CIE paper 4

Question 1

Suggest reasons why species is becoming an endangered species

Answer 1

habitat destruction / deforestation ;
disease ;
fall in prey numbers / difficulty in finding food ;
increased competition (with other carnivores) ;
ref. named human activities ; ; e.g. killing / agriculture / logging
R pollution

Question 2

Describe two other methods of conserving endangered species

Answer 2

national parks ;
zoos ;
captive breeding programmes ;
AVP ; e.g. banning hunting / gamete banks / education qualified

Question 3

recessive allele.

Answer 3

form / variety / version, of a gene ;

only affects phenotype when dominant allele not present / AW ;

Question 4

Explain how viruses input alleles into cells

Answer 4

viral DNA carries normal, allele / gene ;

virus binds cells
viral DNA put into host DNA

Question 5

In some people with cystic fibrosis, the allele has a single-base mutation which produces
a ‘nonsense’ (stop) codon within the gene.
(i) Explain how this mutation would prevent normal CFTR protein being produced

Answer 5

1. translation will not occur normally ;
2. no amino acid added to chain when stop codon reached ;
3. protein chain not completed / protein only partially made ;

Question 6

Outline the hybridoma method for the production of a monoclonal antibody.

Answer 6

2
3
4
5
6
7
(mouse) injected with antigen ; A protein / red cells
spleen / plasma / B, cell ;
with ability to make antibody ; linked to 2
fused with, tumour / myeloma / cancerous, cell ;
cells cultured ;
cells checked for antibody production ;
cells cloned ;

Question 7

State the name of the hormone that is involved in the control of the water potential of
the blood.

Answer 7

ADH ;

Question 8

) Explain the role of isolating mechanisms in the evolution of new species

Answer 8

allopatric speciation ;
geographical isolation / spatial separation ;
e.g. of barrier ;
e.g. of organism ; must relate to 3
sympatric speciation ;
example ;
meiosis problems ;
polyploidy ;
behavioural / temporal / ecological / structural, isolation ;
(isolated) populations, prevented from interbreeding / can only breed
amongst themselves ;
no, gene flow / gene mixing, (between populations) ;
different selection pressures operate ;
natural selection ;
change in allele frequencies ;
different gene pool ;
over time (differences prevent interbreeding) ;
reproductively isolated ;

Question 9

Explain the role of isolating mechanisms in the evolution of new species. [8]
(b) Describe and explain, using an example, the process of artificial selection.

Answer 9

humans ; must be linked to, choosing / selecting / mating etc
parents with desirable feature ;
e.g. organism and feature ;
bred / crossed ;
select offspring with desirable feature ;
repeat over many generations ;
increase in frequency of desired allele(s) / decrease in frequency of
undesired allele(s) ;
background genes ;
loss of hybrid vigour / increase in homozygosity / ref. inbreeding depression ;
AVP ; e.g. detail of breeding techniques

Question 10

Explain what is meant by the term endangered species

Answer 10

species threatened with extinction ;
numbers reduced to critical level / population too small ;
such low numbers that reproduction is affected ;

Question 11

Discuss possible ways in which the squirrel monkey could be protected.

Answer 11

(maintain colony) in zoo ;
captive breeding (programme) ;
assisted reproduction ; e.g. IVF
educate public ;
national parks / conservation areas ;
habitat protection ;
ban, hunting / poaching ;

Question 12

Asellus aquaticus is a small freshwater crustacean.
200 A. aquaticus were released into a pond where there had previously been none. The
pond was favourable for their growth and reproduction.
Describe and explain the expected changes in the population size of A. aquaticus over
the following few months

Answer 12

population increases slowly at first / ref. lag phase ;
(because) adjusting to pond environment ;
(then) steep increase / log phase / exponential increase / rapid
growth or reproduction phase ;
(because) abundant food source / named other factor ;
stationary phase ;
fall in population size / death phase / decline phase ;
(due to) predation / build up of waste ;
competition for named resource ; e.g. food shortage
idea of further increase and fall / ref. population size may be cyclic ;

Question 13

Explain why variation is important in natural selection.

Answer 13

variation means the presence of different characteristics ;
resulting in different survival rates / AW ;
(leads to) reproductive, success / failure ;

Question 14

explain why using bacteria immobilised in alginate rather than agar would be a
more cost-effective production of protease.

Answer 14

1. can use alginate (beads) many times ;
2. (reduces cost of), materials / energy / labour ;
3. fewer bacterial cultures needed / less time spent immobilising
   bacteria ;
4. more protease produced (per hour) (using alginate) ;
5. can run fermentation for longer time ;
6. less time wasted between fermentations ;
   answers must imply comparison

Question 15

Explain why hybridisation between emmer wheat and goat grass 2 would have produced
a sterile hybrid, if doubling of chromosome number had not occurred.

Answer 15

unable to, breed / reproduce ;
to produce fertile offspring ;
reproductively isolated ;

Question 16

With reference to Fig. 4.1, suggest why Triticum urartu and Triticum turgidum are
classified as different species.

Answer 16

species split into two populations by (geographical) barrier ;
different, selection pressures / (environmental) conditions, (on the
two populations) ;
different features, selected / advantageous ;
change in, gene pools / allele frequencies ;
(over time) become unable to interbreed ;

Question 17

Outline how geographical isolation may result in speciation

Answer 17

species split into two populations by (geographical) barrier ;
different, selection pressures / (environmental) conditions, (on the
two populations) ;
different features, selected / advantageous ;
change in, gene pools / allele frequencies ;
(over time) become unable to interbreed ;

Question 18

) Explain briefly the need to discuss the result of the test with a genetic counsellor.

Answer 18

outcome of test needs explanation / counsellor gives advice on
options ;
already have one affected child to care for or problems / cost, of care ;
ref. termination ;
life expectancy increasing with improved drugs ;
gene therapy, not as yet successful / likely to be temporary ;
possibility of, pre-implantation genetic diagnosis (PGD) / artificial
insemination by donor sperm (AID), on another occasion ;

Question 19

Explain what is meant by the term dominant

Answer 19

dominant
(allele) that always expresses itself in the phenotype when present /
(allele) which influences the phenotype even in the presence of an
alternative allele / AW ;

Question 20

Explain the benefits of maintaining biodiversity.

Answer 20

cultural / aesthetic / leisure, reasons ;

moral / ethical, reasons ; e.g. right to exist / prevent extinction

resource material ; e.g. wood for building / fibres for clothes / food for
humans

ecotourism ;

economic benefits ;

ref. resource / species, may have use in future / AW ; e.g. medical use

maintains, food webs / food chains ; A description

nutrient cycling / protection against erosion ;

climate stability ;

maintains, large gene pool / genetic variation ;

Question 21

Describe the mode of action of penicillin on bacteria.

Answer 21

1 penicillin inhibits, enzyme / peptidase ;

2 blocks / alters shape of, active site ;

3 peptidoglycan chains cannot link up / stops cross-links forming ;

4 cell wall weaker / AW ;

5 turgor of cell not resisted (by cell wall) / AW ;

6 cell / wall / bacterium, bursts ;

Question 22

Explain why penicillin does not affect viruses.

Answer 22

1 viruses do not have cell wall ;

2 viruses do not have cytoplasm ;

3 viruses do not have peptidoglycan ;

4 viruses do not have peptidase ;

Question 23

Explain

(i) how a mutation of a gene coding for an enzyme may result in an enzyme with reduced activity,

Answer 23

1 changes in, base / nucleotide, sequence ; A named change
e.g. substitution

2 alters, triplet code / codon ;

3 enzyme has different, primary structure / amino acid sequence ;

4 enzyme has different, 3D structure / tertiary structure / active site ;

Question 24

) Explain the role of natural selection in the evolution of antibiotic resistance in bacteria

Answer 24

1

2

3

4
antibiotic, is selective agent / provides selective pressure ;

resistant bacteria, survive / reproduce ;

pass allele for resistance to offspring ;

frequency of allele in population increases ;

Question 25

Suggest why isolating the mRNA coding for insulin in a ` cell is easier than isolating the DNA for insulin in a ` cell.

Answer 25

1 mRNA (found in β cells) is only from gene coding for insulin / AW ; 2 large numbers (of mRNA coding for insulin) ; 3 (whereas) DNA has all genes ; 4 (so) restriction enzymes needed

Question 26

Deepwater rice is the main food crop in many parts of the world that undergo flooding in the rainy season. Many varieties of deepwater rice have lower yields than non-deepwater varieties. Suggest how a deepwater rice variety with high yield could be produced, using artificial selection.

Answer 26

breed deepwater variety with (high-yielding) non-deepwater variety ; 2. identify / select, offspring with both deepwater response and high yield ; 3. breed selected offspring (with both deepwater response and high yield) ; 4. continue for many generations ;

Question 27

steps for genetic modification

Answer 27

obtain copies of gene with sticky ends the gene codes for the synthesis of insulin use restriction endonuclease enzyme to produce ‘sticky ends’ or cut at specific, site / sequence ; mix vector and gene gene inserts into, vector / plasmid or forms recombinant DNA / AW ; (use DNA) ligase ; to seal the sugar-phosphate backbone insert, plasmid / vector, into host / E. coli / bacteria ; to obtain transformed host E. coli cells screen n for, and obtain, successfully transformed cells so only recombinant host cells cultured ref. batch / continuous, culture or fermenter or bacterial cloning / population growth ; to obtain large amounts of insulin for extraction and purification

Question 28

Explain the meaning ofdominant

Answer 28

dominant (allele) that always expresses itself (in the phenotype) when present or (allele) which influences the phenotype even in the presence of an alternative allele

Question 29

Explain the meaning of gene.

Answer 29

gene length of DNA / sequence of nucleotides, coding for a (specific) polypeptide ; A protein

Question 30

Explain why single-cross hybrids are genetically uniform, but double-cross hybrids are not.

Answer 30

. single-cross hybrids have homozygous parents ; 2. each has inherited the same alleles ; 3. (so) they are uniformly heterozygous ; 4. double-cross hybrids have heterozygous parents ; 5. each has inherited different combinations of alleles or (mixture of) homozygous dominant, homozygous recessive and heterozygous hybrids

Question 31

Describe the reasons why a named species has become endangered

Answer 31

four relevant reasons for a named species ; ; ; ; e.g. animal species direct human effect e.g. hunting / fishing / collection / skins habitat destruction climate change qualified increase in pollution spread / increase, in disease or new disease lack of food increased predation e.g. plant species direct human effect e.g. specimen collection / logging habitat destruction climate change qualified increase in pollution spread / increase, in disease or new disease loss of pollinators increased competition from introduced plants

Question 32

Explain what is meant by a gene mutation and outline the possible consequences of a gene mutation for an organism.

Answer 32

1. chance / random / spontaneous ; 2. change in, base / nucleotide, sequence (in DNA) ; 3. during DNA replication ; 4. base substitution ; 5. often no effect / silent mutation / may code for same amino acid ; 6. base addition / base deletion ; 7. have great effect on phenotype ; 8. frame shifts ; 9. alters whole sequence of bases after mutation ; 10. may lead to stop codon ; 11. different / new, allele ; 12. protein, different shape / different function / not made ;

Question 33

Describe the main features of an organism belonging to the plant kingdom

Answer 33

1. multicellular ; 2. (cells are) differentiated into tissues ; 3. autotrophic / photosynthetic ; 4. eukaryotic (cells); 5. starch is storage compound ; 6. (some have) chloroplasts / chlorophyll ; 7. cell wall ; 8. made of cellulose ; 9. plasmodesmata ; 10. large (central) vacuole

Question 34

Explain how the principles of artificial selection would have been used to produce golden retrievers with the characteristics required for a guide dog.

Answer 34

1 (ideal characteristics) selected by humans / AW ; 2 one example of features ; e.g. calm temperament / obedient / intelligent 3 allowed to mate / bred together ; 4 offspring with ideal characteristics chosen to mate ; 5 over (many) generations ; 6 allele frequency (for ideal characteristics) increases ; 7 directional selection ; [max 4]

Question 35

The monoclonal antibody made by the hybridoma method is modified to obtain humanised mouse antibody. This type of antibody molecule resembles those produced by humans. Suggest advantages of using humanised mouse antibody rather than mouse antibody

Answer 35

1 does not act as foreign antigen / AW ; 2 (so) does not cause, immune response / rejection ; 3 avoids, allergic reactions / side effects / anaphylactic shock ; 4 allows more than one treatment ; 5 remains in body for longer (so more effective) ;

Question 36

State the role of each of these enzymes in producing recombinant DNA carrying the gene for human insulin. reverse transcriptase

Answer 36

reverse transcriptase: produces (c)DNA from mRNA ;

Question 37

State the role of each of these enzymes in producing recombinant DNA carrying the gene for human insulin DNA polymerase

Answer 37

DNA polymerase: produces double stranded DNA from, single stranded (DNA) / cDNA ;

Question 38

State the role of each of these enzymes in producing recombinant DNA carrying the gene for human insulin DNA ligase

Answer 38

DNA ligase: joins (gaps in) the sugar-phosphate backbone (of DNA) ; [4]

Question 39

State the role of each of these enzymes in producing recombinant DNA carrying the gene for human insulin restriction enzyme

Answer 39

cuts, DNA / plasmid

Question 40

a) List three reasons why it is important to conserve endangered plant species

Answer 40

1 maintains biodiversity ; 2 maintain, genetic diversity / genetic variation / gene pool ; 3 (loss of a species) may affect food, chains / webs ; 4 use by humans ; e.g. medical use / building materials / food 5 (eco)tourism ; 6 ethical / moral / aesthetic, reasons ;

Question 41

Explain why high genetic diversity is important for a species

Answer 41

1 idea of better chance of survival in changing conditions ; 2 example of change ; e.g. climatic / increased competition / new disease / new pest 3 less chance of, two harmful recessive alleles coming together / inbreeding depression ;

Question 42

Explain why storing seeds may be a more successful method of conservation than maintaining a population of growing plants

Answer 42

1 idea that seeds are small and easier to store ; 2 seeds can be stored for a long time ; 3 little maintenance required ; 4 less prone to, disease / being eaten ; 5 seeds can be stored anywhere in the world ;

Question 43

Suggest why a sample of each type of seed stored in a seed bank is germinated every few years.

Answer 43

1 to check that seeds are still, viable / able to germinate ; 2 to produce new plants from which fresh seeds can be collected ; 3 to, find / verify, conditions for breaking seed dormancy (should plants be needed) ; [max 2]

Question 44

Explain what is meant by a recessive mutation

Answer 44

V recessive only expressed in homozygote / two copies of the allele needed to be expressed / not expressed in heterozygote / not expressed in presence of dominant allele ; mutation change in the structure of, DNA / gene / allele or change in, base / nucleotide, sequence ;

Question 45

Explain the term sex linkage.

Answer 45

allele / gene, carried on the X chromosome

Question 46

PCR Steps

Answer 46

step 1 DNA sample heated to 95 °C 1 to, separate the two strands / denature DNA ; A make single-stranded DNA 2 by breaking hydrogen bonds (between bases) ; 3 so that bases are exposed ; 4 to produce template strands for (complementary) copying ; step 2 cooled to 65 °C then primers added because 1 (primer) binds / anneals, to DNA by complementary base pairing ; 2 idea of attaching close to the specific section of DNA ; 3 (DNA) polymerase only attaches to double-stranded DNA ; 4 (primers) reduce re-annealing of separated strands step 3 incubated at 72 °C with Taq polymerase, complementary strands of DNA synthesised. the taq 1 synthesises complementary DNA strands ; 2 (Taq polymerase), is heat stable / works at high temperature ; 3 (so) does not need to be added again for each cycle / needs replacing only after a number of cycles ; or other polymerases need replacing regularly ; 4 process is, more efficient / faster (than normal DNA polymerase) ; step 4 heated to 95 °C again and process repeated

Question 47

Suggest what actions may have been necessary at local, national and global levels to contribute to the successful conservation of biodiversity

Answer 47

four from 1 education / awareness, programmes ; 2 compensation scheme / incentives, (needed for farmers who have livestock preyed upon) ; 3 ban, hunting / poaching ; 4 ref. to population monitoring ; 5 international / cross-border, agreement / laws ; 6 ref. to WWF / CITES / trade agreements ; 7 ref. to zoos / reserves / national parks ; 8 captive breeding / sperm banks ; 4

Question 48

Body composed of single isolated cells. Heterotrophic eukaryotic cells without a cell wall. Organism motile.

Answer 48

protoctista

Question 49

Body composed of a mass of undifferentiated cells. Heterotrophic eukaryotic cells with a chitin cell wall. Not motile.

Answer 49

fungi

Question 50

Body composed of a small ball of undifferentiated cells. Autotrophic eukaryotic cells with a cellulose cell wall and flagellum. Organism motile

Answer 50

protoctista

Question 51

Body complex and multicellular, differentiated into a variety of tissues and organs. Heterotrophic eukaryotic cells with no cell wall, some cells have flagellae. Organism motile.

Answer 51

Animalia

Question 52

Body a string of tiny undifferentiated cells. Heterotrophic prokaryotic cells with a peptidoglycan (murein) cell wall. Not motile

Answer 52

prokaryote

Question 53

Body complex and multicellular, differentiated into a variety of tissues and organs. Autotrophic eukaryotic cells with a cellulose cell wall. Not motile.

Answer 53

plant

Question 54

Suggest the advantages and disadvantages of such a two-kingdom classification compared to the five kingdom classification often used today.

Answer 54

advantages IDEA of simplicity; easy to classify most organisms into the correct kingdom; consistent with the traditional literature / AW; disadvantages plant kingdom, is artificial / contains unrelated organisms / organisms that are not fundamentally similar; ref. to prokaryotes and eukaryotes in the same kingdom; ref. to other valid example of very differently organised organisms in the same kingdom; problem of what to do with protoctists / AW; detail of difficulty with protoctists (e.g. Euglena is motile (animal-like) but autotrophic (plantlike);

Question 55

how is the plasmid DNA is cut

Answer 55

restriction (endonuclease) enzyme; named example; e.g. EcoR1 specific, sequence of bases/point; ref. to sticky ends/exposed bases

Question 56

Explain how the human insulin gene is joined to the plasmid DNA.

Answer 56

sticky ends added to insulin gene; ref. to complimentary base pairing/C and G bases pair up; ref. H bonds; (DNA) ligase; formation of phosphodiester bond/seals sugar phosphate backbone;

Question 57

List two advantages of treating diabetics with human insulin produced by genetic engineering.

Answer 57

identical to human insulin (ref. to bovine/porcine insulin used previously); ref. to reduced immune response/side effects; cheaper to produce; more rapid response; pure/uncontaminated; regular production not dependent on livestock; ethical issues; AVP; e.g. tolerance

Question 58

Beer contains ethanol. Suggest and explain the role of yeast enzymes in beer production

Answer 58

6 (a) anaerobic / in absence of oxygen; glycolysis; IDEA OF because if it was aerobic, no ethanol / only carbon dioxide and water, would be produced; sugar(s) / named sugar is respiratory substrate; ethanol produced; carbon dioxide produced

Question 59

Most beers contain starch. Recently, ‘light’ beers of low energy content have become more popular. Light beers have a low starch content. This is achieved by the addition of immobilised fungal amylase after the mashing process. (i) Explain the advantage of using immobilised enzymes in this process

Answer 59

end product not contaminated; enzyme, more stable/less likely to be denatured; enzyme recovery easier; idea of enzyme being reused; AVP; e.g. cost

Question 60

a) Describe why variation is important in natural selection.

Answer 60

ref. continuous/discontinuous variation; 2 genetic/inherited variation; 3 variation in phenotype/characteristics/AW; 4 (can be due to) interaction of genotype and environment; 5 e.g. of characteristic that influences survival; 6 ref. intraspecific competition/struggle for existence; 7 those with favourable characteristics survive/AW; 8 pass on favourable characteristics to offspring; 9 those with disadvantageous characteristics die

Question 61

b) Explain the role of isolating mechanisms in the evolution of new species

Answer 61

10 ref. to definition of species; 11 ref. allopatric; 12 geographical isolation; 13 ref. to examples e.g. islands/lakes/mountain chains/idea of barrier; 14 ref. to example organism; 15 ref. to populations prevented from interbreeding; 16 isolated populations subjected to different selection pressures/conditions; 17 over time sufficient differences to prevent interbreeding; 18 ref. sympatric; 19 ref. to reproductive isolation; 20 ref. behavioural barriers (within a population); 21 e.g. day active/night active; 22 correct ref. to gene pool; 23 change to allele frequencies;

Question 62

Explain what is meant by the term heterozygous

Answer 62

two different alleles of a gene / different allele pair for a gene / AW ; produces gametes with different genotypes ; (max 1)

Question 63

Explain what is meant by the term genotype.

Answer 63

alleles present in an organism / particular alleles of a gene / genetic constitution / AW ;

Question 64

Explain how the change from an extensive lake system to just a few pools could have resulted in the evolution of four species of desert pupfi sh.

Answer 64

any fi ve from: 1. allopatric speciation ; 2. fi sh populations isolated ; 3. geographical / physical / land, barrier ; 4. no, breeding / allele fl ow / gene fl ow, between populations ; 5. mutations occur ; 6. different selection pressures / different (environmental) conditions ; 7. advantageous alleles selected for / advantageous alleles passed on ; 8. change in, allele frequency / gene pool ; 9. (can result in) different chromosome numbers ; 10. genetic drift ; 11. ultimately, reproductively isolated / cannot interbreed ;

Question 65

Suggest what may happen to the desert pupfi sh if water levels rise and the pools once more form an extensive lake system.

Answer 65

1. numbers of all species increase initially ; 2. due to more, breeding space / food ; 3. competition between (four) species ; 4. (possible) reduction in numbers within, some / all, species ; 5. not all species (may) survive ; 6. different species, restricted to different areas / occupy different niches ; 7. interbreeding / hybridisation ; 8. AVP ; e.g. ref. new selection pressure

Question 66

Explain how the lac operon is involved in the metabolism of lactose in Escherichia coli.

Answer 66

1. regulatory gene codes for repressor protein ; 2. (repressor protein) binds to operator region ; 3. (repressor protein) blocks promoter region ; 4. lactose binds to repressor protein which changes shape ; 5. (repressor protein with bound lactose) breaks away from operator region ; 6. promoter region now unblocked, so RNA polymerase binds to promoter region ; 7. structural genes transcribed ; 8. and translated ; 9. enzymes formed ; 10. ref. lactose permease and uptake of lactose from medium ; 11. ref. β-galactosidase and breakdown of lactose ; 12. into, glucose / galactose ;

Question 67

Describe the role of gibberellin in the germination of barley.

Answer 67

1. DELLA proteins inhibit germination ; 2. seed absorbs water ; 3. stimulates production of gibberellin ; 4. by embryo ; 5. gibberellin causes breakdown of DELLA proteins ; 6. leads to transcription of mRNA coding for amylase ; 7. in aleurone layer ; 8. (amylase) hydrolyses starch to maltose ; 9. ref. maltose converted to glucose ; 10. glucose respired by embryo during germination

Question 68

Explain how allopatric speciation is occurring in the house mouse populations of Madeira.

Answer 68

mouse populations separated by mountains ; no, breeding / gene flow, between populations ; mutations occur ; different selection pressures / different (environmental) conditions ; genetic change ; e.g. different alleles selected for / change in allele frequency / change in gene pool / advantageous alleles passed on ; (results in) different chromosome numbers ; genetic drift ; (different populations ultimately) cannot interbreed ; R different species

Question 69

Suggest why Gram-positive bacteria are more susceptible to the action of penicillin than Gram-negative bacteria

Answer 69

assume gram+ unless otherwise stated (gram+) penicillin can reach, cell wall / peptidoglycan, directly /AW / (gram-) ora ; (gram-) outer membrane provides protection (from penicillin) / (gram+) ora ; (gram+) more % peptidoglycan in wall (so greater effect from penicillin) / (gram-) ora ;

Question 70

Describe the parts of the pancreas involved in its endocrine function.

Answer 70

islets of Langerhans ; scattered throughout pancreas / AW ; alpha and beta cells ; blood supply (to carry hormones away) ;

Question 71

Explain the benefits of maintaining biodiversity

Answer 71

cultural / aesthetic / leisure, reasons ; moral / ethical, reasons ; e.g. right to exist / prevent extinction resource material ; e.g. wood for building / fibres for clothes / food for humans ecotourism ; economic benefits ; ref. resource / species, may have use in future / AW ; e.g. medical use maintains, food webs / food chains ; A description nutrient cycling / protection against erosion ; climate stability ; maintains, large gene pool / genetic variation

Question 72

Explain how an addition mutation could produce a stop triplet.

Answer 72

(addition / insertion), of a, base / nucleotide, to DNA / to a gene ; 2. changes a, sequence of three bases / triplet / codon ; ignore ref. to frame shift 3. (triplet) no longer codes for an amino acid ;

Question 73

Explain how a marker gene, such as the gene for GFP, is used to show successful uptake of a gene for a wanted protein

Answer 73

1. marker gene linked to gene for wanted protein ; 2. with promoter ; 3. GFP gene is, transcribed / expressed ; 4. producing GFP which fluoresces ; [3 max]

Question 74

Genes for enzymes that produce fluorescent substances are often used as markers in gene technology. GFP is not an enzyme. Suggest one disadvantage of using the gene for GFP to produce easily detectable fluorescence, rather than using a gene for an enzyme that produces a fluorescent substance. Explain your answer.

Answer 74

disadvantage 1. may not fluoresce very brightly / may be difficult to detect ; explanation 2. only a few molecules of GFP produced ; 3. each enzyme molecule produces more fluorescent substance /

Question 75

Suggest how human activities could damage coral reefs.

Answer 75

any three from 1. named marine pollutant ; e.g. oil / sewage 2. example of climate change ; e.g. sea level rising / change in sea temperature / decrease in oxygen concentration of sea 3. (increasing carbon dioxide) decrease in pH of sea ; 4. intensive fishing ; 5. tourism qualified ; 6. removal of parts of reef ; 7. reclaiming land ; [3 max]

Question 76

Discuss the link between the frequency of sickle cell anaemia and the number of cases of malaria.

Answer 76

accept alternative symbols for alleles throughout 11. frequency of sickle cell anaemia is highest in areas where malaria is common ; 12. sickle cell anaemia red blood cells cannot carry oxygen very well / AW ; A sickling blocks capillaries 13. homozygous HS / HSHS, have sickle cell anaemia / may die ; 14. homozygous HN / HNHN, have normal, Hb / red blood cells ; 15. heterozygotes, have sickle cell trait or (sickle cell trait) red blood cells not (severely) affected ; 16. malaria parasite / Plasmodium, affects red blood cells ; 17. malaria lethal ; 18. sickle cell trait people / heterozygotes, less likely to suffer from (severe effects of) malaria ; 19. have selective advantage ; 20. pass on both HN and HS ; 21. malaria selects against, homozygous HN / HNHN ; 22. sickle cell anaemia selects against, homozygous HS / HS HS ; 23. idea that sickle cell allele is maintained within population because of sickle cell trait individuals

Question 77

Describe the main features of an organism belonging to the plant kingdom

Answer 77

1. multicellular ; 2. (cells are) differentiated into tissues ; 3. autotrophic / photosynthetic ; 4. eukaryotic (cells); 5. starch is storage compound ; 6. (some have) chloroplasts / chlorophyll ; 7. cell wall ; 8. made of cellulose ; 9. plasmodesmata ; 10. large (central) vacuole

Question 78

Explain what is meant by a gene mutation and outline the possible consequences of a gene mutation for an organism

Answer 78

. 1 chance / random / spontaneous ; 2. change in, base / nucleotide, sequence (in DNA) ; 3. during DNA replication ; 4. base substitution ; 5. often no effect / silent mutation / may code for same amino acid ; 6. base addition / base deletion ; 7. have great effect on phenotype ; 8. frame shifts ; 9. alters whole sequence of bases after mutation ; 10. may lead to stop codon ; 11. different / new, allele ; 12. protein, different shape / different function / not made

Question 79

locus

Answer 79

position of gene on chromosome

Question 80

Describe the properties of plasmids that make them suitable for their roles in genetic engineering.

Answer 80

three from 1 small ; 2 circles (of DNA) ; 3 contain genes (for enzymes) to enable DNA transfer to plant cells ; 4 contain, restriction sites / polylinkers ; 5 own origin of replication / can multiply independently ; 6 ref. to marker genes ; 3

Question 81

The life cycle of Plasmodium is very complex, with a number of stages. The stages that infect human beings are haploid. Suggest why the Hardy-Weinberg principle cannot be used to calculate the frequency of the allele for chloroquine resistance.

Answer 81

(parasites are) haploid / not diploid ; do not reproduce (only) sexually ; (no need to calculate as) percentage of parasites killed = frequency of non-resistant allele ; ora percentage of parasites surviving = frequency of resistant allele AVP ; Hardy-Weinberg principle requires, random mating / no migration / no mutation / no selection

Question 82

Discuss whether or not an individual tree can be described as a small, distinct ecosystem

Answer 82

ref. to interactions between, biotic and abiotic (components) ; yes tree supports, many species / community / many interactions ; energy flow / food web, occurs on one tree ; no idea that tree is part of larger ecosystem / interactions occur with organisms outside tree ; part of, savannah / larger, energy flow / food web / nutrient recycling

Question 83

Outline the disadvantages of using plants that have been genetically modified.

Answer 83

GM seed could be difficult for farmers in developing countries to obtain ; 2 high cost of (buying) GM seed / cannot use own seed ; 3 too expensive for, people to buy / farmers to sell ; 4 might reduce efforts to relieve poverty ; 5 may not grow well in all conditions (as other traits not selected for) ; 6 ref. to possible, allergic reactions in humans / toxicity of more herbicide left after use / adverse effects on the immune system ; 7 under-developed countries becoming more dependent on other countries ; 8 cross-pollination with, wild plants / organic crops ; 9 new more resistant weeds / “superweeds” ; 10 ref. to loss of traditional varieties ; 11 loss of genetic diversity ; 12 harm to other species ; e.g. effect on rest of food chain

Question 84

Outline the advantages of captive breeding programmes

Answer 84

1 supplied with food ; 2 monitor health of the, mother / offspring ; 3 (sperm / eggs) stored / frozen ; A sperm bank 4 artificial insemination / in vitro fertilisation ; A AI / IVF 5 ref. to cloning / surrogacy / fostering (of young) ; 6 fertilised eggs incubated artificially ; 7 transfer of breeding partners between zoos ; 8 maintenance of records ; 9 maintains genetic diversity ; 10 protection from, predators / shooting / disease

Question 85

Suggest why animals in captive breeding programmes may not always breed successfully

Answer 85

1 no longer living in natural habitat ; 2 stress ; 3 behavioural changes ; 4 idea of disruption to normal reproductive cycles ; 5 reject mate

Question 86

) When animals that have been bred in captivity are released, their survival rate is low. Suggest two reasons why many of these animals are unable to survive in the wild

Answer 86

1 may find difficulty in moving around (due to previously been captive) ; 2 idea of difficulty obtaining food / short of food / outcompeted for food ; 3 difficulty integrating with others of members of their species ; 4 disease ; 5 idea of lack of survival skills ; A lack of fear of, humans / predators

Question 87

Suggest why some methods of manufacturing genetically engineered insulin use eukaryotic yeast cells rather than prokaryotic bacterial cells.

Answer 87

1 in yeast cells promoters already present ; 2 have RER / Golgi body ; 3 so, insulin can be modified / insulin is in correct 3D conformation ; 4 AVP ; e.g. ref. to YAC holding more DNA than BAC

Question 88

Outline the main operating conditions of continuous culture

Answer 88

1 performed in an open fermenter / nutrients added at a steady rate throughout ; 2 products harvested throughout ; 3 pH / temp / oxygen concentration, controlled throughout ; 4 ref. to input = output / constant volume ; [max 2]

Question 89

State three advantages of using continuous culture and not batch culture, for the mass production of these enzymes.

Answer 89

1 organisms maintained in exponential phase ; 2 faster rate of enzyme production ; 3 no build-up of toxins ; 4 no down time / AW ; 5 small vessels can be used ; 6 cost effective

Question 90

Outline the advantages of using immobilised enzymes in the treatment of textile waste water

Answer 90

1 enzyme can be, re-used / recovered after use ; 2 enzyme does not contaminate water / no purification needed ; 3 idea of enzymes being thermostable ; 4 idea that enzymes able to withstand pH changes ; 5 ref. to increased shelf-life of enzyme

Question 91

Suggest explanations for the decrease in the number of marine animal species between 1950 and 2000

Answer 91

pollution ; environment / habitat, change qualified ; e.g. increase in water temperature / change in water pH overfishing ; loss of food / more competition for food ; direct human interference qualified ; e.g. pleasure boats

Question 92

Explain what is meant by the term biodiversity.

Answer 92

variety of / different / total number of, species ; genetic diversity of species / AW ;

Question 93

Discuss the benefits of maintaining the biodiversity of a marine ecosystem, such as that in the coastal waters of Canada.

Answer 93

any three from tourism / leisure ; economic benefits ; food for humans ; ref. resource / species, may have use in future / AW ; maintains, food webs / food chains ; A description nutrient cycling ; maintains, (large) gene pool / genetic variation ;

Question 94

(b) Explain, using examples, how the environment may affect the phenotype of an organism.

Answer 94

phenotypic variation results from interaction of genotype and environment / VP = VG + VE ; environment may modify expression of gene(s) ; must be stated e.g. for size / mass / height ; because, food / nutrient / ion, missing or in short supply ; A malnutrition named, food / nutrient / ion, (missing or in short supply) ; environment may, trigger / switch on, gene ; must be stated ref. low temperature and change in animal colour ; ref. high temperature and, curled wing in Drosophila / gender in crocodiles ; ref. UV light and melanin production ; ref. wavelength of light and, flowering / germination / fruit colour ; other named trigger plus example ; environment effect usually greater on polygenes / ora ; environment may induce mutation affecting phenotype ;

Question 95

Suggest methods to conserve the Bengal Tiger

Answer 95

1. stop killing ; 2. education ; 3. stop trade in tiger parts ; 4. zoos / national parks ; 5. captive breeding / AW ; 6. release back into wild ; 7. replant forests / AW ; 8. protect remaining forest / stop deforestation ; 9. AVP ; e.g. incentives to indigenous people / ban use in circuses or as pets

Question 96

The Bengal Tiger belongs to the kingdom Animalia. State two differences between members of the kingdom Animalia and the kingdom Plantae

Answer 96

1. heterotrophic / AW ; 2. locomotion ; ora 3. male gametes motile ; ora 4. detail cell structure ; e.g. no cell wall / no tonoplast ora ignore ref. to cellulose

Question 97

a summary of the main principles of artificial selection.

Answer 97

Some of the words have been omitted. Write the most appropriate term in each space. When humans purposefully apply selection pressure. to members of a population, the process is known as artificial selection. For example, people have tried to ‘improve’ their cattle for thousands of years. It is desirable for a dairy farmer to have cows with a high milk yield. The farmer will select cows with high milk yields and mate them with bulls whose female relatives have high milk yields. Some of the alleles conferring high milk yield are passed onto their female offspring who are then chosen for breeding. This will continue for many generations Artificial selection can have disadvantages such as inbreeding depression which can lead to infertility.

Question 98

Suggest how the stocks of Atlantic cod may be increased.

Answer 98

1. stop / reduce, fishing ; A correct ref. to quotas / moratorium 2. ref. to size of nets ; 3. ref. to methods of fishing ; 4. control pollution ; 5. education ; 6. captive breeding and release / restocking from fish farms ; 7. ref. to marine reserves

Question 99

Explain the role of allopatric isolating mechanisms in the evolution of new species.

Answer 99

1. (same) species separated into separate populations ; 2. (by) geographical isolation / named example ; 3. prevents interbreeding between populations / no gene flow ; 4. ref. to different selection pressures ; 5. change in allele frequencies ; 6. eventually do not successfully interbreed ; 7. allopatric speciation ; 8. ref. to genetic drift / founder effect / different mutations / (different) new alleles

Question 100

Coelacanth haemoglobin has a very high affinity for oxygen, suggesting that coelacanths, which have been captured at depths of between 200 m and 400 m, live in water that has a low concentration of oxygen. Explain how an environmental factor, such as the low concentration of oxygen in deep water, can act: (i) as a stabilising force in natural selection

Answer 100

1. idea of, unchanging / constant, environment ; 2. oxygen concentration acts as a selective agent ; 3. organisms best adapted to these conditions survive ; ora 4. extreme (phenotypes) selected against ; 5. ref. narrow range of genetic variation / allele frequency maintained ; 6. sketch graph ; 7. ref. mutation ;

Question 101

Coelacanth haemoglobin has a very high affinity for oxygen, suggesting that coelacanths, which have been captured at depths of between 200 m and 400 m, live in water that has a low concentration of oxygen. Explain how an environmental factor, such as the low concentration of oxygen in deep water, can act: (ii) as an evolutionary force in natural selection.

Answer 101

1. ref. change in oxygen concentration ; 2. (low) oxygen concentration acts as selective agent ; 3. some individuals (in population) are better adapted ; 4. these are more likely to survive ; ora 5. directional selection ; 6. sketch graph ; 7. populations develop in different concentrations of oxygen ; 8. disruptive selection ; 9. sketch graph ; allow either mp6 or mp9 but not both

Question 102

Explain how a population of A. porcatus that became isolated on an island could evolve into a new species.

Answer 102

1 allopatric speciation ; 2 (lizard populations) separated by water ; 3 geographical/physical, barrier ; 4 no, breeding/gene flow, between populations ; 5 mutations occur ; 6 different selection pressures/different (environmental) conditions ; 7 genetic change ; e.g. different alleles selected for/change in allele frequency/ change in gene pool/advantageous alleles passed on ; 8 (can result in) different chromosome numbers ; 9 genetic drift ; 10 ultimately, reproductively isolated/cannot interbreed

Question 103

Explain what is meant by the term gene mutation.

Answer 103

change in, DNA/base sequence ; produces different allele ; ref. different, protein/polypeptide, produced

Question 104

Explain what is meant by the term species.

Answer 104

1. similar, morphological / physiological / biochemical / behavioural, features ; 2. interbreed / reproduce, to produce fertile offspring ; 3. occupy same niche ; 4. reproductively isolated

Question 105

what happens during an immune response

Answer 105

1. ref. antigen presenting cells ; 2. (antigen) A recognised as, non-self / AW ; 3. by B lymphocytes; 4. with appropriate, receptor / antibody / immunoglobulin ; 5. ref. clonal selection ; 6. (B lymphocytes) clonal expansion / mitosis / cell division ; 7. T-helper cells to stimulate B-cell (response) ; 8. release cytokine; 9. (B lymphocytes) mature into plasma cells ; 10. (plasma cells) secrete (anti-A) antibody ;

Question 106

Variable number tandem repeats (VNTRs) are repetitive, non-coding sections of DNA. A particular VNTR is located at the same locus in different individuals, but the number of repeats in that VNTR varies between individuals. (a) Explain how, in the process of genetic fingerprinting, gel electrophoresis is able to distinguish between the VNTRs that occur at the same loci of different individuals.

Answer 106

1. VNTRs with more repeats are, longer / greater mass ; ora 2. phosphate groups (of DNA) give negative charge ; 3. fragments / DNA, attracted to, anode / positive electrode ; 4. Shorter / lower mass / fewer repeat, pieces move, faster / further in unit time; ora 5. ref. impedance of gel / AW ;

Question 107

Suggest reasons for maintaining plant biodiversity

Answer 107

1. (some, species / plants / animals may have) uses in the future ; 2. medical uses / example ; 3. resource material ; e.g. wood for building / fibres for clothes / food (for humans) / agriculture ; 4. ecotourism ; 5. maintain, gene pool / genetic diversity ; 6. prevention of natural disasters ; 7. aesthetic reasons ; 8. to maintain stability in, ecosystems / food chains

Question 108

State why a man who has haemophilia is unable to pass the condition on to his son.

Answer 108

passes Y chromosome onto son / passes X chromosome onto daughter ;

Question 109

State the term used to describe the genotype of a carrier and Suggest how become a carrier.

Answer 109

heterozygous ;

Question 110

Explain why, in many examples of gene technology, fluorescent markers are used in preference to antibiotic resistance genes.

Answer 110

1. easier to, identify/screen; 2. more economical/time saving/labour saving; 3. resistance gene(s) can be passed to other bacteria; 4. idea of antibiotics no longer effective OR requiring development of new, antibiotics/treatments;

Question 111

Explain why, in gene technology, a promoter needs to be transferred along with the desired gene

Answer 111

1. promoter, initiates transcription/switches on gene/causes gene expression/AW; 2. ref. binding of, RNA polymerase/transcription factors; 3. otherwise gene has to be inserted near an existing promoter; 4. this is difficult to do/this may disrupt expression of existing gene; 5. in eukaryotes precise position of promoter important;

Question 112

Explain what is meant by the term continuous culture

Answer 112

1. nutrients added and product removed at a steady rate/AW; 2. (so) volume kept constant; 3. organism kept at, exponential/log, phase of growth

Question 113

) After about six weeks, mutants may appear in the fungal population, for example, a more highly-branched form of the fungus. The fermenter is emptied, cleaned and repopulated with the original strain of F. venenatum every six weeks. Explain why the fermentation process should be stopped before mutants appear.

Answer 113

v1. (branched fungus tangles together in clumps so) too heavy for bubbles to, lift/stir OR ref. to blocking; 2. difficult to, harvest/get desired texture; 3. mutant may be, harmful when eaten/toxic/allergenic; 4. mutant may produce, distasteful/coloured, substance; 5. mutant may be less productive; 6. mutant may have high concentration of RNA (which is difficult to lower); 7. approval for sale only applies to original strain;

Question 114

Suggest why populations, such as that of the small squirrel, do not increase in size indefinitely.

Answer 114

1. limiting/density dependent, factors or described; 2. reached carrying capacity/AW; 3. competition/AW; 4. for, food/nesting sites/resources; 5. large population attracts predators; 6. large population spreads disease more easily;

Question 115

Suggest why some animals became extinct in this area but the other mammals did not.

Answer 115

1. not many to begin with; 2. are carnivorous; 3. prey numbers fell; 4. slower reproductive rate; 5. more likely to migrate (to other areas);

Question 116

(a) Explain the need to maintain biodiversity in an ecosystem such as a tropical rainforest

Answer 116

1. cultural/aesthetic / leisure, reasons; 2. moral/ethical, reasons ; e.g. right to exist/prevent extinction; 3. resource material ; e.g. wood (for building)/fibres for clothes/food for humans/(herbal) medicine 4. (eco)tourism; 5. economic benefits; 6. ref. resource / species, may have use in future/AW; e.g. medical use 7. maintains, food webs / food chains; A description 8. nutrient cycling; 9. protection against erosion; 10. climate stability; 11. maintains, (large) gene pool/genetic variation; 12. scientific research;

Question 117

Outline how DNA sequencing could be used to compare the DNA

Answer 117

(total) DNA / genome, cut into fragments ; by restriction enzymes ; DNA, denatured / made single stranded ; ref. primers / (modified) PCR ; ref. dideoxynucleotides / chain termination ; DNA / Taq, polymerase ; copies of different lengths produced ; electrophoresis ; A description detection, of fluorescence / by laser scanner ; sequence of, bases / nucleotides, read (by computer) ;

Question 118

query With reference to any named species of plant or animal, explain why this species is considered to be endangered and outline the reasons that have caused it to become endangered.

Answer 118

fall in numbers ; danger of becoming extinct ; ref. (IUCN / International Union for Conservation of Nature) / red list ; one mark for idea, additional mark if qualified with point specific to named example e.g. habitat destruction ; detail ; climate change ; detail ; e.g. rise in temperature increase in disease ; detail ; increase in, predators / grazers ; detail ; decrease in food ; detail ; named pollutant and habitat affected ; detail ; hunting / killing / poaching / removal (plant) ; detail ; e.g. trade in animal parts, selling rare plants increased competition ; detail ; lack of human education ; detail ; disturbance to breeding sites ; detail ; [max 8]

Question 119

It has been stated that the kingdom Protoctista can be described as a very diverse group of organisms that share only a few common features. Discuss the ways in which members of the kingdom Protoctista are similar to each other and ways in which they differ

Answer 119

) similarities eukaryotic (cells) ; detail of eukaryotic cell ;; e.g. nucleus / ``` linear DNA / chromosomes associated with histones / (named) membrane-bound organelles / 80S ribosomes ``` differences single-celled or colonial / multicellular ; autotrophic or heterotrophic ; motile or unable to move ; cell wall or no cell wall ; vacuole or no vacuole ; different life cycles ; [max 7]

Question 120

Explain how multiple alleles arise

Answer 120

gene mutation ; a change in the, base(s) / ``` nucleotide(s) ; e.g. base, substitution / deletion / addition ```

Question 121

Describe how the gene coding for human insulin can be obtained and inserted into a plasmid vector.

Answer 121

1 obtain mRNA from β cells (of islets of Langerhans of pancreas) ; 2 reverse transcriptase ; 3 make (single-stranded) cDNA ; 4 DNA polymerase used to make cDNA double stranded ; 5 sticky ends created ; A description 6 (obtain) plasmids ; 7 cut with restriction, endonuclease / enzyme ; A named e.g. EcoR1 8 ref. complementary sticky ends ; 9 cDNA / insulin gene, mixed with plasmid ; 10 DNA ligase ; 11 seals nicks in sugar-phosphate backbone ; R anneals

Question 122

Explain how bacteria can be genetically modified and then identified using antibiotic resistance genes.

Answer 122

1 (recombinant) plasmids mixed with bacteria ; 2 (some) bacteria, take up plasmids / transformed ; 3 heat shock / calcium chloride solution / Ca 2+ ions / electroporation ; to identify bacteria containing plasmids 4 grow on, agar / medium, containing antibiotic (A) ; A ampicillin 5 plasmid contains, antibiotic (A) / ampicillin, resistance gene(s) ; 6 bacteria with plasmid survive ; ora to identify recombinant bacteria 7 replica plate ; A description e.g. sponge / velvet pad / absorbent paper 8 (onto) agar / medium, containing second antibiotic (B) ; A tetracycline 9 (tetR / B / 2nd) resistance gene inactivated (by insertion of new, DNA / gene) / AW ; 10 (ID) colonies from, 1st / ampicillin, plate that do not grow on, 2nd / tetracycline, plate ;

Question 123

Describe the advantages of using batch culture for penicillin production and continuous culture for mycoprotein production.

Answer 123

) batch / penicillin 1 nutrients, decrease / run out ; 2 so, secondary metabolite / penicillin, made ; 3 fermenters can be used (after cleaning) for different process ; 4 if problem occurs only one batch affected ; 5 needs little, monitoring / attention (once set up) ; continuous / mycoprotein 6 (fungus) kept in, exponential / log, phase (of growth) ; 7 (so) high, biomass / yield / production rate ; 8 little / no, downtime ; 9 small, vessels / space, required; 10 cost-effective ;

Question 124

(b) Outline the hybridoma method for the production of a monoclonal antibody.

Answer 124

1 mouse is injected with an antigen ; 2 wait for immune response to occur ; 3 clonal selection ; A description e.g. antigen binds to, specific / virgin, B cell 4 clonal expansion ; A description e.g. mitosis / division / cloning of B cells 5 B-lymphocytes / plasma cells, are extracted ; 6 from the mouse’s spleen ; 7 fused with, cancer / myeloma / tumour, cells ; 8 hybridoma cells formed ; 9 hybridoma cells producing antibodies are identified ; 10 cultured on a large scale (to secrete monoclonal antibodies) ; [max 7]

Question 125

Define the term bioinformatics

Answer 125

database(s) ; computer (programs) / software ; analysis of, data / biological information / sequences ; A compare, genes / genomes

Question 126

Outline how sequencing the genome of Plasmodium and the use of bioinformatics can suggest new targets for anti-malarial drugs.

Answer 126

1 identify / recognise, gene(s) ; A find where genes are 2 predict, primary structure / amino acid sequences, of proteins ; 3 predict 3D structure of proteins ; A tertiary 4 identify / predict, functions of proteins (from 3D structure) ; 5 ref. to drug to, bind with / block activity of / disrupt structure of, protein / enzyme ; A drug specific to protein I denature, protein / enzyme 6 drug prevents, transcription / expression, (of gene) ; I gene editing

Question 127

Suggest advantages of using theoretical models in this research, rather than testing possible drugs in the laboratory.

Answer 127

cheaper ; A more economic(al) faster / can try many different drugs in a short period of time ; A time-saving can try out changes to, model / drug structure, to see if more effective ; no need for, laboratories / equipment ; I uses less labour (initially) no need for tests on, animals / humans ; A fewer ethical issues

Question 128

Suggest why theoretical modelling cannot completely replace laboratory trials in the search for new drugs.

Answer 128

functionality / to test that drug, actually works / is effective ; A cannot assume predictions are correct I efficiency safety ; A ref. to clinical trials / side effects dosage ; A theoretical modelling will not give information on doses [max 2]

Question 129

Name and describe a method for estimating the abundance of water voles in a local area

Answer 129

1 mark-release-recapture / AW ; A catch, mark, return, catch A mark-and-recapture description (max 3) 2 detail of trapping ; e.g. Longworth / Sherman / live / small mammal 3 detail of marking ; e.g. felt tip pen / clipping fur / not to have adverse effects 4 detail of timing of second trapping ; e.g. not too soon or mixing will not occur / not too long after as migration may occur / after 24 hours / ``` 1 day (any number of days up to two weeks) 5 detail of calculation ; e.g. Lincoln Index / Petersen index or number marked time 1 × no. captured time 2 number of marked individuals recaptured time 2 A symbols in equation if key is given ```

Question 130

Discuss the reasons why alien species should be controlled.

Answer 130

1 reduce, other organisms’ abundance / biodiversity ; A endanger, rare species / water voles A causes extinction 2 alter food, chains / webs ; 3 due to predation ; 4 due to competition ; 5 due to spreading disease ; 6 may change habitat ; e.g. create shade, change soil pH 7 may be toxic / threaten human health

Question 131

Explain what is meant by the term homeostasis

Answer 131

maintaining a constant internal environment ; AW R external I body conditions [1] start

Question 132

Outline the differences between structural and regulatory genes.

Answer 132

I polypeptide throughout structural gene 1 structural protein / enzyme / ``` rRNA ; A any named protein other than a transcription factor (e.g. transporter / receptor / named hormone / ``` immunoglobulin / haemoglobin / etc.) R if any of these are identified as product of regulatory gene 2 named, structural protein / other protein / enzyme, or tRNA ; R named protein if function wrongly described 3 idea that needed for, structure / function, of cell ; regulatory gene 4 (product) controls, gene expression / transcription ; A promote / prevent / start / stop, gene expression or transcription 5 (codes for) transcription factor / DNA-binding protein ; 6 binds to, promoter / operator / DNA response element ; 7 stops / allows, binding of RNA polymerase ; 8 ref. to repressor / repressible ; A silencer 9 ref. to inducer / inducible ; A activator / enhancer 10 named example of regulatory gene ; A lac repressor / DELLA repressor / homeobox or homeotic or Hox gene [max 6]

Question 133

Explain the economic reasons for maintaining biodiversity.

Answer 133

economic 1 (some, species / plants / animals may have) uses in the future ; 2 medical uses / example ; 3 resource material ; e.g. wood for building / fibres for clothes 4 food (for humans) / agriculture ; 5 tourism / example ; 6 ref. maintain gene pool / genetic diversity ; 7 prevention of natural disasters ; 8 AVP ; e.g. ref. biological control (predators / parasites reduce pest populati

Question 134

Outline the principles of electrophoresis as used in sequencing this DNA

Answer 134

1 cut DNA (into fragments) ; 2 by, restriction enzymes / named enzyme ; 3 place on (agarose) gel ; 4 apply, current / p.d. / electricity ; 5 fragments travel towards anode ; 6 short fragments travel, further / faster, than long ones ; A mass of fragments 7 visualise DNA with UV light / other means of visualisation ; 8 AVP ; e.g. Southern blotting / described

Question 135

) Outline how artificial selection differs from natural selection

Answer 135

``` artificial selection selection (pressure by) humans genetic diversity lowered inbreeding common loss of vigour / inbreeding depression increased homozygosity / decreased heterozygosity no isolation mechanisms operating (usually) faster selected feature for human benefit not for, survival / evolution ``` natural selectiom environmental selection pressure ; genetic diversity remains high ; outbreeding common ; increased vigour / less chance of inbreeding depression ; decreased homozygosity / increased heterozygosity ;isolation mechanisms do operate ; (usually) slower ;selected feature for organism’s benefit ;promotes, survival / evolution

Question 136

Explain why batch culture, rather than continuous culture, is used for the production of penicillin.

Answer 136

marking points refer to batch culture 1 (penicillin) is a secondary, metabolite / product ; R Penicillium 2 more penicillin is produced (per unit time) ; A higher yield comparative statement 3 in the later stages of growth (of the culture) / after main growth phase is over ; 4 (penicillin produced when, fungus / Penicillium,) is short of nutrients ; R no nutrients left alternative points for 2 and 3 for continuous culture (ora) 2a less penicillin is produced (per unit time) ; comparative statement 3a continuous culture remains in, exponential / active growth, phase ;

Question 137

explain the importance of the plasmid having a single target site for a particular restriction enzyme

Answer 137

single target site will be in correct resistance gene ; 2 (gene to be inserted has) complementary sticky ends to target site sticky ends ; 3 more cuts would fragment plasmid

Question 138

Describe the use of one alternative marker gene that can be used instead of an antibiotic gene

Answer 138

1 gene for fluorescent substance ; 2 source of gene ; e.g. from jellyfish 3 substance fluoresces when exposed to appropriate light ; or 4 lacZ gene / gene for β-galactosidase ; 5 splits non-blue substrate ; 6 product is blue ;

Question 139

Explain how natural selection may bring about evolution

Answer 139

13 individuals in population have great reproductive potential / AW ; 14 numbers in population remain roughly constant ; 15 variation in members of population ; 16 environmental factors / named factor (biotic or abiotic) ; linked to 17 and 18 17 (cause) many, fail to survive / die / do not reproduce ; 18 those best adapted survive / survival of the fittest ; 19 (reproduce to) pass on alleles ; R genes 20 genetic variation leads to change in phenotype ; 21 ref: changes in, gene pool / allele frequency ; 22 over time produces evolutionary change ; 23 new species arise from existing ones / speciation ; 24 directional / stabilising, selection ; [8 max]

Question 140

In 1987, the world population of black-footed ferrets consisted of only 18 animals living in captivity. A number of different agencies worked together to prevent the extinction of this species. Their goal was to produce young black-footed ferrets to be released into the wild. The survival and breeding of the animals in the wild would then be monitored and supported. The collaborating agencies included: • local government • universities • zoos • native tribes that owned undeveloped reservation land. Outline how these different agencies could contribute to successful conservation of the black-footed ferret.

Answer 140

1 (local government) authorities, education / pass protection laws / create protected zones ; 2 (universities) carry out research ; 3 example of relevant research ; e.g. improve success of breeding programme do IVF monitor genetic variability coordinate stud records determine suitable habitat requirements for release sites monitor wild populations 4 (zoos) run captive breeding (programmes) / description ; 5 native Americans / reservations / tribes, provide suitable habitat

Question 141

Explain the benefits of using frozen sperm in captive breeding programmes

Answer 141

1 increases number of, breeding stock / potential mates ; 2 larger gene pool / increase in genetic variation ; 3 sperm transported to other, zoos / breeding facilities ; 4 (frozen / stored), sperm acts as gene bank ; 5 alleles available from animals no longer alive ;

Question 142

Discuss the advantages of screening for genetic conditions.

Answer 142

1 information about the increased risk of person having genetic conditions ; 2 ref. breast cancer / named example ; 3 allows people to prepare for late onset genetic conditions ; 4 ref. Huntington’s disease / Alzheimer’s disease / named example ; 5 identify whether fetuses are going to develop a genetic condition ; 6 so can give early treatment when born ; 7 allows parents to prepare for the birth of a child who will need treatment for a considerable time or even throughout life / AW ; 8 identifies carriers of genetic conditions ; 9 helps to provide early diagnosis ; 10 allows couples who are both carriers of a genetic condition to make decisions about starting a family / having more children / seeking IVF ; 11 AVP ; e.g. termination

Question 143

Discuss the potential advantages of growing genetically modified crops, using examples to help your answer.

Answer 143

1 increase, food production / crop yields ; 2 improve food, quality / taste / keeping properties ; 3 add nutrients to crop (to improve human health) ; 4 crops may be more tolerant to climate change ; 5 crops, can be grown in poor quality land / do not need as much fertiliser ; 6 pest / insect / fungal disease, resistance (increases crop growth) ; 7 less pesticide used ; 8 benefit to farmer ; e.g. cost effective / health benefit 9 benefit to environment ; e.g. less effect on food chains, pollinators 10 herbicide resistance reduces competition from weeds ; 11 could engineer nitrogen-fixing ability in non-leguminous crops ; 12 specific examples (crop variety and enhancement described) ; ; + e.g. Golden Rice™ for extra vitamin A 13 Bt maize / Bt cotton, kill (named) leaf-eating insects Flavr Savr tomato, stores better / can ripen on vine

Question 144

Explain the use of genes for fluorescent or easily stained substances as markers in gene technology.

Answer 144

1 emits bright light ; 2 when exposed to UV light ; 3 visible colour change ; 4 add marker gene to the, vector / plasmid ; 5 easy to identify transformed bacteria ; 6 gene of interest inserted, into / close to, marker gene ; 7 easy to identify recombinant, DNA / plasmid ; 8 easy to identify transgenic organisms ; 9 examples ; e.g. GFP / β galactosidase / GUS 10 idea of no known risk ; [

Question 145

Outline how sequencing the genome of Plasmodium and the use of bioinformatics can suggest new targets for anti-malarial drugs

Answer 145

identify / recognise, gene(s) ; A find where genes are 2 predict, primary structure / amino acid sequences, of proteins ; 3 predict 3D structure of proteins ; A tertiary 4 identify / predict, functions of proteins (from 3D structure) ; 5 ref. to drug to, bind with / block activity of / disrupt structure of, protein / enzyme ; A drug specific to protein I denature, protein / enzyme 6 drug prevents, transcription / expression, (of gene) ; I gene editing [max 3]

Question 146

Describe how the gene coding for human insulin can be obtained and inserted into a plasmid vector.

Answer 146

1 obtain mRNA from β cells (of islets of Langerhans of pancreas) ; 2 reverse transcriptase ; 3 make (single-stranded) cDNA ; 4 DNA polymerase used to make cDNA double stranded ; 5 sticky ends created ; A description 6 (obtain) plasmids ; 7 cut with restriction, endonuclease / enzyme ; A named e.g. EcoR1 8 ref. complementary sticky ends ; 9 cDNA / insulin gene, mixed with plasmid ; 10 DNA ligase ; 11 seals nicks in sugar-phosphate backbone ; R anneals

Question 147

) Explain how bacteria can be genetically modified and then identified using antibiotic resistance genes.

Answer 147

1 (recombinant) plasmids mixed with bacteria ; 2 (some) bacteria, take up plasmids / transformed ; 3 heat shock / calcium chloride solution / Ca 2+ ions / electroporation ; to identify bacteria containing plasmids 4 grow on, agar / medium, containing antibiotic (A) ; A ampicillin 5 plasmid contains, antibiotic (A) / ampicillin, resistance gene(s) ; 6 bacteria with plasmid survive ; ora to identify recombinant bacteria 7 replica plate ; A description e.g. sponge / velvet pad / absorbent paper 8 (onto) agar / medium, containing second antibiotic (B) ; A tetracycline 9 (tetR / B / 2nd) resistance gene inactivated (by insertion of new, DNA / gene) / AW ; 10 (ID) colonies from, 1st / ampicillin, plate that do not grow on, 2nd / tetracycline, plate

Question 148

Describe the advantages of using batch culture for penicillin production and continuous culture for mycoprotein production.

Answer 148

batch / penicillin 1 nutrients, decrease / run out ; 2 so, secondary metabolite / penicillin, made ; 3 fermenters can be used (after cleaning) for different process ; 4 if problem occurs only one batch affected ; 5 needs little, monitoring / attention (once set up) ; continuous / mycoprotein 6 (fungus) kept in, exponential / log, phase (of growth) ; 7 (so) high, biomass / yield / production rate ; 8 little / no, downtime ; 9 small, vessels / space, required; 10 cost-effective ;

Question 149

Explain what is meant by heterotrophic.

Answer 149

c) (i) idea of feeding on other organisms ; | to obtain organic compounds

Question 150

Outline how an enzyme can be immobilised in alginate

Answer 150

1. (solutions of) alginate and enzyme mixed ; 2. droplets (of mixture) into calcium chloride (solution) ; 3. to produce beads ;

Question 151

State two advantages, of using an immobilised enzyme in an industrial process compared with the same enzyme that has not been immobilised.

Answer 151

stability 1. idea of easier purification of product ; 2. enzyme, can be reused / is not lost / has longer shelf life ; 3. allows continuous culture ; 4. cheaper

Question 152

summary of the main principles of natural selection

Answer 152

Individuals in a population have great reproductive potential and yet the numbers in a population remain roughly .stable . This is because many die due to environmental factors and therefore do not reproduce. There is variation amongst members of a population and those with the features best adapted to the environment survive. They reproduce and pass on their alleles to their offspring. This may lead to a change in the gene pool of the population and over time may lead to evolutionary change.

Question 153

triplet code

Answer 153

triplet code 4. (sequence of) three (DNA nucleotide) bases ; 5. complementary to mRNA codon ; 6. codes for a specific amino acid ;

Question 154

Explain why genes for enzymes that produce fluorescent substances are used as makers in gene technology

Answer 154

1 identification of transformed, cells/organisms ; 2 avoid use of antibiotics ; 3 easy to detect ; 4 no known ill effect on GM organism ;

Question 155

Explain what is meant by continuous variation and explain why this type of variation occurs in a population

Answer 155

) range of, phenotypes / ``` heights ; AW normal distribution ; A described or drawn polygenic / genes or alleles have an additive effect ; environment has an effect ; named environmental factor ; e.g. nutrients / light intensity / (soil) water availability / ``` ``` soil pH / soil mineral availability / disease or pest attack ``` / temperature / wind

Question 156

Outline three characteristic features of members of Eukarya

Answer 156

``` 1 (cells) have a nucleus ; 2 (cells) contain membrane-bound organelles ; A mitochondria / ER / golgi 3 ribosomes are, large / 22 nm / 80S ; 4 DNA is linear ; 5 histones present ; 6 ref. to cytoskeleton / microtubules / undulipodia / cilia ; ```

Question 157

Explain how non native species could cause problems for local biodiversity

Answer 157

1 may compete with other species for, food / habitat ; 2 may be predators of other species ; 3 may spread disease to other species ; 4 may reduce population sizes / cause extinction of other species ; 5

Question 158

b) Describe the genetic control of protein production in a prokaryote using the lac operon

Answer 158

1 ref. to regulatory gene ; 2 codes for repressor protein ; 3 (repressor protein) binds to operator ; In presence of lactose 4 lactose binds to repressor protein ; A allolactose 5 (repressor protein) changes shape ; 6 (repressor protein), moves away from / no longer binds to, operator ; In absence of lactose 7 repressor protein blocks promoter or promoter region now unblocked ; 8 RNA polymerase cannot bind to promoter or RNA polymerase can now bind to promoter ; 9 (named) gene cannot be transcribed / mRNA not synthesised or (named) gene now, transcribed / ‘switched on’ ; 10 enzymes / named enzyme, cannot be synthesised or enzymes / named enzyme, can now be synthesised ; [max 7]

Question 159

Suggest why increasing genetic diversity could help to conserve populations of a species.

Answer 159

1 reduces likelihood of harmful recessive alleles coming together ; 2 to prevent, inbreeding depression / reduced vigour ; ora 3 increases ability (of population) to adapt to changing environment ; ora 4 increases chances of survival when exposed to, pathogen / disease ;

Question 160

Explain how artificial selection works

Answer 160

humans (as selective agent) ; offspring with ideal characteristics chosen to mate ; repeated over many generations ; allele frequency for ideal characteristics increases ; directional selection

Question 161

characteristics that may be selected for when carrying out artificial selection in cattle

Answer 161

any two from docility / AW ; ref. to milk production ; high fertility ; hornlessness ; ref. to meat production ; disease resistance

Question 162

Suggest problems that may result from inbreeding.

Answer 162

inbreeding depression / lack of hybrid vigour ; 2 more chance that harmful recessive alleles may be expressed ; 3 decrease in heterozygosity / increase in homozygosity ; 4 less genetic variation ; [max 3]

Question 163

Describe how electrophoresis is used in genetic fingerprinting

Answer 163

1 ref. to VNTR (sequences) ; 2 quantity of DNA increased by PCR ; 3 DNA fragmented by, restriction enzyme(s) / endonuclease(s) ; 4 loaded (into wells) in agarose gel ; 5 (at) negative end / cathode end ; 6 ref. to buffer / electrolyte ; 7 direct current applied ; 8 phosphate groups of DNA give negative charge ; 9 (negatively charged) DNA attracted to, anode / positive electrode ; 10 short pieces / smaller mass, move further / move faster ; ora 11 (pieces) transferred to, membrane / nylon / nitrocellulose / absorbent paper or Southern blotting ; 12 heated to separate strands ; 13 probes / fluorescent dye, added ; 14 X-ray film / UV light / lasers ; 15 pattern of stripes / ref. banding pattern

Question 164

Describe how an enzyme can be immobilised in alginate and discuss the advantages of using an immobilised enzyme.

Answer 164

a) description 1 enzyme mixed with sodium alginate (solution) ; 2 placed in syringe ; 3 added drop by drop ; 4 to (solution of) calcium chloride ; 5 beads (with enzyme) formed ; 6 beads separated from calcium chloride ; 7 wash with water ; advantages 8 (enzyme) can be re-used ; 9 product, uncontaminated / enzyme-free ; 10 (so) purification not needed / less downstream processing ; 11 reduces cost ; 12 works at higher temperature / thermostable ; 13 works in changed pH ; 14 reaction, can be fast(er) / have high(er) yield ;

Question 165

artificial selection

Answer 165

by humans ; individuals with desired features chosen to breed / AW / named example

Question 166

Describe the methods used to conserve endangered animal species

Answer 166

place in zoos ; protected against, disease / predation ; captive breeding programme ; ref. assisted reproduction / cloning / sperm banks ; released into wild ; ref. national parks / reserves ; rangers patrol parks ; human access restricted ; controlled agriculture ; controlled industry ; visitor centres / education ; habitat / breeding sites, protected ; banning sale of protected animals or their products ; banning hunting ;

Question 167

Describe the advantages of the batch culture method and the continuous culture method

Answer 167

batch easy to set up culture ; can continue with minimal attention / AW ; environmental conditions easy to control ; fermenter can be used for different process afterwards ; only waste one batch if contaminated ; less chance of blockage in fermenter ; continuous no / less, down time / AW ; small vessels can be used ; productivity high ; cost effective ; downstream processing easier ; good for using immobilised enzymes

Question 168

Describe the production of penicillin using the batch culture method

Answer 168

use Penicillium (in batch fermenter) ; (main) nutrients added at start ; penicillin only produced, after growth phase / when running out of nutrients ; (penicillin) is a secondary metabolite ; fermentation is stopped ; penicillin is harvested ; fermenter is cleaned out / ref. sterility ; new culture of Penicillium is put in and started again ; ref. fed batch culture ; carbohydrate / named nutrient, added regularly ; keeps fermentation going longer / produces more penicillin ; detail of fermenter ;; e.g. paddle to mix nutrients / sterilising steam inlet / set at pH 6.5 / aeration / kept at 27 °C [max 8]

Question 169

Suggest two advantages of growing GM rice

Answer 169

1 reduces deficiency disease/AW ; 2 better quality food ; 3 assistance to developing nations/AW ; 4 cheap seed ; e.g. for golden rice

Question 170

Suggest two disadvantages of growing GM crops.

Answer 170

high cost of GM seed ; 2 too much power held by multinational companies ; 3 change to ecosystem ; e.g. hybridisation 4 GM crops may be difficult to sell ; 5 GM plant varieties may be genetically unstable ; 6 no long term studies done on effects on human health ; 7 reduction in biodiversity/outcompetes natural variety or species ;

Question 171

Explain why genes for enzymes that produce fluorescent substances are used as makers in gene technology

Answer 171

identification of transformed, cells/organisms ; 2 avoid use of antibiotics ; 3 easy to detect ; 4 no known ill effect on GM organism

Question 172

Maize, Zea mays, is a major cereal food crop. Unlike most crop plants, maize seed is produced by hybridisation between two different inbred parental strains. (a) (i) Explain why this is done.Suggest one disadvantage of producing seed in this way

Answer 172

1. hybrid vigour ; 2. increased heterozygosity / decreased homozygosity ; 3. increases gene pool / AW ; 4. harmful recessive alleles less likely to be expressed / reduces inbreeding depression ; 5. increased yield ; 6. other named useful characteristic ; e.g. disease resistance / more nutritious [3 max] (ii) high cost (of seed) / farmers must buy new seed each year

Question 173

The following passage is a summary of the main principles of natural selection. Some of the words have been omitted. Write the most appropriate term in each space. Individuals in a population have great ......................................................... potential and yet the numbers in a population remain roughly ......................................................... . This is because many die due to environmental factors and therefore do not reproduce. There is ......................................................... amongst members of a population and those with the features best adapted to the environment survive. They reproduce and pass on their ......................................................... to their offspring. This may lead to a change in the ......................................................... pool of the population and over time may lead to evolutionary change.

Answer 173

``` reproductive ; constant / stable / AW ; variation ; alleles ; gene ; ```

Question 174

triplet code

Answer 174

triplet code 4. (sequence of) three (DNA nucleotide) bases ; 5. complementary to mRNA codon ; 6. codes for a specific amino acid ;

Question 175

Explain how gel electrophoresis separates these fragments of DNA

Answer 175

1. fragments are separated according to, length / mass ; 2. phosphate groups (of DNA) give negative charge ; 3. fragments move to, anode / positive electrode ; 4. short / light, fragments move, faster / further in unit time / ora ; must be comparative 5. ref. impedance of gel / AW ;

Question 176

Explain why a promoter was inserted into the plasmid

Answer 176

(ii) 1. (promoter required) to ensure expression of the (introduced) genes / AW ; 2. (suitable promoter) might not be present in the rice cells ; 3. (suitable promoter) might not be in the correct position relative to the introduced genes ;

Question 177

Explain why the fungus needs sources of carbon and nitrogen

Answer 177

carbon or nitrogen source 1. to produce, amino acids / proteins / enzymes; 2. to produce, nucleic acids / nucleotides / ATP / purines / pyrimidines / named N-base; 3. chitin / building block, for cell wall; carbon only 4. used in respiration; 5. to produce, carbohydrates / sugar / polysaccharide / glycogen / lipids

Question 178

Explain what is meant by the term continuous culture.

Answer 178

nutrients added and product removed at a steady rate / AW; 2. (so) volume / named condition, kept, constant / at an optimum; 3. organism kept at, exponential / log, phase of growth; [2 max]

Question 179

v Outline the principles of gel electrophoresis. (ii) Explain how the presence of the gene for DsRed in a moth can be confirmed once electrophoresis is complete. ..................................................................................................................................

Answer 179

© Cambridge International Examinations 2013 (b) (i) 1. DNA fragmented by, restriction enzyme(s) / endonuclease(s); 2. loaded (into wells) at, negative end / cathode end, (of gel); 3. ref. buffer / electrolyte; 4. phosphate groups of DNA give negative charge; 5. (negatively charged) DNA attracted to, anode / positive electrode; 6. separation due to, electric field / PD / potential difference; 7. short pieces / smaller mass, move further (in unit time) / move faster; ora 8. ref. impedance of gel / AW; [4 max] (ii) 1. idea of comparison of position with reference DNA; 2. ref. staining / fluorescence in UV; 3. by use of DNA probe; 4. ref. single-stranded / complementary base pairing;

Question 180

) Describe the methods used to conserve endangered animal species

Answer 180

place in zoos ; protected against, disease / predation ; captive breeding programme ; ref. assisted reproduction / cloning / sperm banks ; released into wild ; ref. national parks / reserves ; rangers patrol parks ; human access restricted ; controlled agriculture ; controlled industry ; visitor centres / education ; habitat / breeding sites, protected ; banning sale of protected animals or their products ; banning hunting ;

Question 181

Mycoprotein is produced using a continuous culture method. Describe the advantages of the batch culture method and the continuous culture method. [7] [Total

Answer 181

batch easy to set up culture ; can continue with minimal attention / AW ; environmental conditions easy to control ; fermenter can be used for different process afterwards ; only waste one batch if contaminated ; less chance of blockage in fermenter ; continuous no / less, down time / AW ; small vessels can be used ; productivity high ; cost effective ; downstream processing easier ; good for using immobilised enzymes ;

Question 182

Describe the production of penicillin using the batch culture method

Answer 182

use Penicillium (in batch fermenter) ; (main) nutrients added at start ; penicillin only produced, after growth phase / when running out of nutrients ; (penicillin) is a secondary metabolite ; fermentation is stopped ; penicillin is harvested ; fermenter is cleaned out / ref. sterility ; new culture of Penicillium is put in and started again ; ref. fed batch culture ; carbohydrate / named nutrient, added regularly ; keeps fermentation going longer / produces more penicillin ; detail of fermenter ;; e.g. paddle to mix nutrients / sterilising steam inlet / set at pH 6.5 / aeration / kept at 27 °C [max 8]

Question 183

a) Describe the main features of an organism belonging to the plant kingdom.

Answer 183

multicellular ; differentiated cells ; (most) have, vascular tissue / xylem and phloem ; eukaryotic (cells) ; ref. meristems ; (most) are not motile ; motile gametes only in mosses and ferns ; autotrophic nutrition / photosynthesis ; cells have: chloroplasts ; large / central, vacuole ; walls made of cellulose ;

Question 184

) Outline how DNA analysis can be carried out and then used to establish which male lizard sired each hatchling

Answer 184

details of electrophoresis ;; any 2 from DNA cut by, restriction enzyme(s) / endonuclease(s) loaded (into wells) at, negative end / cathode end, (of gel) ref. buffer / electrolyte (negatively charged) DNA attracted to, anode / positive electrode separation due to, electric field / potential difference short pieces / smaller mass, move further (in unit time) / move faster ora fluorescent / radioactive, DNA probes compare, DNA sequences / bands, (of male lizard and hatchling

Question 185

what is meant by artificial selection

Answer 185

by humans ; individuals with desired features chosen to breed / AW / named example ;

Question 186

) Describe how an enzyme can be immobilised in alginate and discuss the advantages of using an immobilised enzyme.

Answer 186

a) description 1 enzyme mixed with sodium alginate (solution) ; 2 placed in syringe ; 3 added drop by drop ; 4 to (solution of) calcium chloride ; 5 beads (with enzyme) formed ; 6 beads separated from calcium chloride ; 7 wash with water ; advantages 8 (enzyme) can be re-used ; 9 product, uncontaminated / enzyme-free ; 10 (so) purification not needed / less downstream processing ; 11 reduces cost ; 12 works at higher temperature / thermostable ; 13 works in changed pH ; 14 reaction, can be fast(er) / have high(er) yield ;

Question 187

Explain the advantages of treating diabetic people with human insulin produced by gene technology.

Answer 187

1 it is identical to human insulin ; ora 2 (more) rapid response ; ora 3 no / fewer, immune response / side effects / allergic reactions ; ora 4 ref. to ethical / moral / religious, issues ; ora 5 cheaper to produce in large volume / unlimited availability ; ora R cheap to produce 6 less risk of, transmitting disease / infection ; ora 7 good for people who have developed tolerance to animal insulin ; ora

Question 188

Describe how electrophoresis is used in genetic fingerprinting

Answer 188

1 ref. to VNTR (sequences) ; 2 quantity of DNA increased by PCR ; 3 DNA fragmented by, restriction enzyme(s) / endonuclease(s) ; 4 loaded (into wells) in agarose gel ; 5 (at) negative end / cathode end ; 6 ref. to buffer / electrolyte ; 7 direct current applied ; 8 phosphate groups of DNA give negative charge ; 9 (negatively charged) DNA attracted to, anode / positive electrode ; 10 short pieces / smaller mass, move further / move faster ; ora 11 (pieces) transferred to, membrane / nylon / nitrocellulose / absorbent paper or Southern blotting ; 12 heated to separate strands ; 13 probes / fluorescent dye, added ; 14 X-ray film / UV light / lasers ; 15 pattern of stripes / ref. banding pattern ;

Question 189

Artificial selection can result in inbreeding. Suggest problems that may result from inbreeding. ...................................................................................................................................................

Answer 189

1 inbreeding depression / lack of hybrid vigour ; 2 more chance that harmful recessive alleles may be expressed ; 3 decrease in heterozygosity / increase in homozygosity ; 4 less genetic variation ; [max 3]

Question 190

Suggest two other characteristics that may be selected for when carrying out artificial selection in cattle.

Answer 190

v) any two from docility / AW ; ref. to milk production ; high fertility ; hornlessness ; ref. to meat production ; disease resistance ;

Question 191

ain how artificial selection has taken place to produce Santa Gertrudis cattle.

Answer 191

humans (as selective agent) ; 2 shorthorn and Brahman bred together ; 3 offspring with ideal characteristics chosen to mate ; 4 repeated over many generations ; 5 allele frequency for ideal characteristics increases ; 6 directional selection

Question 192

Suggest why increasing genetic diversity could help to conserve populations of Italian agile frogs. ...................................................................................................................................................

Answer 192

reduces likelihood of harmful recessive alleles coming together ; 2 to prevent, inbreeding depression / reduced vigour ; ora 3 increases ability (of population) to adapt to changing environment ; ora 4 increases chances of survival when exposed to, pathogen / disease ; ora [max 3]

Question 193

Describe the genetic control of protein production in a prokaryote using the lac operon

Answer 193

1 ref. to regulatory gene ; 2 codes for repressor protein ; 3 (repressor protein) binds to operator ; In presence of lactose 4 lactose binds to repressor protein ; A allolactose 5 (repressor protein) changes shape ; 6 (repressor protein), moves away from / no longer binds to, operator ; In absence of lactose 7 repressor protein blocks promoter or promoter region now unblocked ; 8 RNA polymerase cannot bind to promoter or RNA polymerase can now bind to promoter ; 9 (named) gene cannot be transcribed / mRNA not synthesised or (named) gene now, transcribed / ‘switched on’ ; 10 enzymes / named enzyme, cannot be synthesised or enzymes / named enzyme, can now be synthesised ;

Question 194

Outline how wheat crops have been improved by selective breeding

Answer 194

``` 1 ref. to humans (select) ; 2 cross / breed, plants with desirable characteristic ; 3 named desirable characteristic ; e.g. bigger ears / more grains per ear / bigger grains / higher yield / fast-growing / tolerance to high temperature / disease-resistant / ``` pest-resistant 4 over several generations ; 5 (only) using offspring with desirable characteristic(s) ; 6 frequency of desirable allele(s) increases ; 7 AVP ; e.g. polyploidy / hybridisation of ancestor grasses

Question 195

Explain what is meant by continuous variation and explain why this type of variation occurs in a population.

Answer 195

range of, phenotypes / ``` heights ; AW normal distribution ; A described or drawn polygenic / genes or alleles have an additive effect ; environment has an effect ; named environmental factor ; e.g. nutrients / light intensity / (soil) water availability / ``` ``` soil pH / soil mineral availability / disease or pest attack ``` / temperature / wind [max 3]

Question 196

Describe a method for estimating the size of a raccoon population in a town.

Answer 196

; AW 2 detail of trapping ; e.g. live mammal trap bait with, food / chocolate / peanut butter 3 detail of marking ; e.g. paint / clipping fur / not to have adverse effects 4 time of second trapping detail ; e.g. not too soon or mixing won’t occur / not too long after as migration may occur 5 detail of calculation ; e.g. Lincoln / Petersen, index or population size = number caught / marked, time 1 x no. captured time 2 number of marked individuals recaptured time 2 6 public reports ; e.g. online site / use of reporting app 7 detail of reporting, time frame / areas ; e.g. raccoon spotting week 8 detail of calculating numbers per unit area / use of computer modelling ;

Question 197

Eukarya

Answer 197

``` ) 1 (cells) have a nucleus ; 2 (cells) contain membrane-bound organelles ; A mitochondria / ER / golgi 3 ribosomes are, large / 22 nm / 80S ; 4 DNA is linear ; 5 histones present ; 6 ref. to cytoskeleton / microtubules / undulipodia / cilia ```

Question 198

It has been suggested that raccoons may threaten biodiversity and pose a risk to human health in Germany. Explain how raccoons could cause problems for local biodiversity and for human health. local biodiversity

Answer 198

1 may compete with other species for, food / habitat ; 2 may be predators of other species ; 3 may spread disease to other species ; 4 may reduce population sizes / cause extinction of other species ; 5 may spread, disease / rabies, to humans ; 6 may bite humans ;