CIE paper 4 Flashcards
Suggest reasons why species is becoming an endangered species
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
Describe two other methods of conserving endangered species
national parks ;
zoos ;
captive breeding programmes ;
AVP ; e.g. banning hunting / gamete banks / education qualified
recessive allele.
form / variety / version, of a gene ;
only affects phenotype when dominant allele not present / AW ;
Explain how viruses input alleles into cells
viral DNA carries normal, allele / gene ;
virus binds cells
viral DNA put into host DNA
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
- translation will not occur normally ;
- no amino acid added to chain when stop codon reached ;
- protein chain not completed / protein only partially made ;
Outline the hybridoma method for the production of a monoclonal antibody.
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 ;
State the name of the hormone that is involved in the control of the water potential of
the blood.
ADH ;
) Explain the role of isolating mechanisms in the evolution of new species
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 ;
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.
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
Explain what is meant by the term endangered species
species threatened with extinction ;
numbers reduced to critical level / population too small ;
such low numbers that reproduction is affected ;
Discuss possible ways in which the squirrel monkey could be protected.
(maintain colony) in zoo ; captive breeding (programme) ; assisted reproduction ; e.g. IVF educate public ; national parks / conservation areas ; habitat protection ; ban, hunting / poaching ;
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
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 ;
Explain why variation is important in natural selection.
variation means the presence of different characteristics ;
resulting in different survival rates / AW ;
(leads to) reproductive, success / failure ;
explain why using bacteria immobilised in alginate rather than agar would be a
more cost-effective production of protease.
- can use alginate (beads) many times ;
- (reduces cost of), materials / energy / labour ;
- fewer bacterial cultures needed / less time spent immobilising
bacteria ; - more protease produced (per hour) (using alginate) ;
- can run fermentation for longer time ;
- less time wasted between fermentations ;
answers must imply comparison
Explain why hybridisation between emmer wheat and goat grass 2 would have produced
a sterile hybrid, if doubling of chromosome number had not occurred.
unable to, breed / reproduce ;
to produce fertile offspring ;
reproductively isolated ;
With reference to Fig. 4.1, suggest why Triticum urartu and Triticum turgidum are
classified as different species.
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 ;
Outline how geographical isolation may result in speciation
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 ;
) Explain briefly the need to discuss the result of the test with a genetic counsellor.
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 ;
Explain what is meant by the term dominant
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 ;
Explain the benefits of maintaining biodiversity.
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 ;
Describe the mode of action of penicillin on bacteria.
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 ;
Explain why penicillin does not affect viruses.
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 ;
Explain
(i) how a mutation of a gene coding for an enzyme may result in an enzyme with reduced activity,
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 ;
) Explain the role of natural selection in the evolution of antibiotic resistance in bacteria
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 ;
Suggest why isolating the mRNA coding for insulin in a ` cell is easier than isolating the DNA for insulin in a ` cell.
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
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.
breed deepwater variety with (high-yielding) non-deepwater variety ;
- identify / select, offspring with both deepwater response and high yield ;
- breed selected offspring (with both deepwater response and high yield) ;
- continue for many generations ;
steps for genetic modification
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
Explain the meaning ofdominant
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
Explain the meaning of gene.
gene
length of DNA / sequence of nucleotides, coding for a (specific) polypeptide ; A protein
Explain why single-cross hybrids are genetically uniform, but double-cross hybrids are not.
. single-cross hybrids have homozygous parents ;
- each has inherited the same alleles ;
- (so) they are uniformly heterozygous ;
- double-cross hybrids have heterozygous parents ;
- each has inherited different combinations of alleles
or
(mixture of) homozygous dominant, homozygous recessive and heterozygous hybrids
Describe the reasons why a named species has become endangered
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
Explain what is meant by a gene mutation and outline the possible consequences of a gene mutation for an organism.
- chance / random / spontaneous ;
- change in, base / nucleotide, sequence (in DNA) ;
- during DNA replication ;
- base substitution ;
- often no effect / silent mutation / may code for same amino acid ;
- base addition / base deletion ;
- have great effect on phenotype ;
- frame shifts ;
- alters whole sequence of bases after mutation ;
- may lead to stop codon ;
- different / new, allele ;
- protein, different shape / different function / not made ;
Describe the main features of an organism belonging to the plant kingdom
- multicellular ;
- (cells are) differentiated into tissues ;
- autotrophic / photosynthetic ;
- eukaryotic (cells);
- starch is storage compound ;
- (some have) chloroplasts / chlorophyll ;
- cell wall ;
- made of cellulose ;
- plasmodesmata ;
- large (central) vacuole
Explain how the principles of artificial selection would have been used to produce golden retrievers with the characteristics required for a guide dog.
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]
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
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) ;
State the role of each of these enzymes in producing recombinant DNA carrying the gene for human insulin.
reverse transcriptase
reverse transcriptase: produces (c)DNA from mRNA ;
State the role of each of these enzymes in producing recombinant DNA carrying the gene for human insulin DNA polymerase
DNA polymerase: produces double stranded DNA from, single stranded (DNA)
/
cDNA ;
State the role of each of these enzymes in producing recombinant DNA carrying the gene for human insulin DNA ligase
DNA ligase: joins (gaps in) the sugar-phosphate backbone (of DNA) ; [4]
State the role of each of these enzymes in producing recombinant DNA carrying the gene for human insulin restriction enzyme
cuts, DNA
/
plasmid
a) List three reasons why it is important to conserve endangered plant species
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 ;
Explain why high genetic diversity is important for a species
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 ;
Explain why storing seeds may be a more successful method of conservation than maintaining a population of growing plants
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 ;
Suggest why a sample of each type of seed stored in a seed bank is germinated every few years.
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]
Explain what is meant by a recessive mutation
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 ;
Explain the term sex linkage.
allele / gene, carried on the X chromosome
PCR Steps
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
Suggest what actions may have been necessary at local, national and global levels to contribute to the successful conservation of biodiversity
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
Body composed of single isolated cells. Heterotrophic eukaryotic cells without a cell wall. Organism motile.
protoctista
Body composed of a mass of undifferentiated cells. Heterotrophic eukaryotic cells with a chitin cell wall. Not motile.
fungi
Body composed of a small ball of undifferentiated cells. Autotrophic eukaryotic cells with a cellulose cell wall and flagellum. Organism motile
protoctista
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.
Animalia
Body a string of tiny undifferentiated cells. Heterotrophic prokaryotic cells with a peptidoglycan (murein) cell wall. Not motile
prokaryote
Body complex and multicellular, differentiated into a variety of tissues and organs. Autotrophic eukaryotic cells with a cellulose cell wall. Not motile.
plant
Suggest the advantages and disadvantages of such a two-kingdom classification compared to the five kingdom classification often used today.
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);
how is the plasmid DNA is cut
restriction (endonuclease) enzyme; named example; e.g. EcoR1 specific, sequence of bases/point; ref. to sticky ends/exposed bases
Explain how the human insulin gene is joined to the plasmid DNA.
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;
List two advantages of treating diabetics with human insulin produced by genetic engineering.
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
Beer contains ethanol. Suggest and explain the role of yeast enzymes in beer production
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
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
end product not contaminated; enzyme, more stable/less likely to be denatured; enzyme recovery easier; idea of enzyme being reused; AVP; e.g. cost
a) Describe why variation is important in natural selection.
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
b) Explain the role of isolating mechanisms in the evolution of new species
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;
Explain what is meant by the term heterozygous
two different alleles of a gene / different allele pair for a gene / AW ; produces gametes with different genotypes ; (max 1)
Explain what is meant by the term genotype.
alleles present in an organism / particular alleles of a gene / genetic constitution / AW ;
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.
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 ;
Suggest what may happen to the desert pupfi sh if water levels rise and the pools once more form an extensive lake system.
- 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
Explain how the lac operon is involved in the metabolism of lactose in Escherichia coli.
- 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 ;
Describe the role of gibberellin in the germination of barley.
- 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
Explain how allopatric speciation is occurring in the house mouse populations of Madeira.
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
Suggest why Gram-positive bacteria are more susceptible to the action of penicillin than Gram-negative bacteria
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 ;
Describe the parts of the pancreas involved in its endocrine function.
islets of Langerhans ;
scattered throughout pancreas / AW ;
alpha and beta cells ;
blood supply (to carry hormones away) ;
Explain the benefits of maintaining biodiversity
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
Explain how an addition mutation could produce a stop triplet.
(addition / insertion), of a, base / nucleotide, to DNA / to a gene ;
- changes a, sequence of three bases / triplet / codon ; ignore ref. to frame shift
- (triplet) no longer codes for an amino acid ;
Explain how a marker gene, such as the gene for GFP, is used to show successful uptake of a gene for a wanted protein
- marker gene linked to gene for wanted protein ; 2. with promoter ; 3. GFP gene is, transcribed / expressed ; 4. producing GFP which fluoresces ; [3 max]
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.
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 /
Suggest how human activities could damage coral reefs.
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]
Discuss the link between the frequency of sickle cell anaemia and the number of cases of malaria.
accept alternative symbols for alleles throughout 11. frequency of sickle cell anaemia is highest in areas where malaria is common ;
- 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
Describe the main features of an organism belonging to the plant kingdom
- multicellular ;
- (cells are) differentiated into tissues ;
- autotrophic / photosynthetic ;
- eukaryotic (cells);
- starch is storage compound ;
- (some have) chloroplasts / chlorophyll ;
- cell wall ;
- made of cellulose ;
- plasmodesmata ;
- large (central) vacuole
Explain what is meant by a gene mutation and outline the possible consequences of a gene mutation for an organism
. 1 chance / random / spontaneous ;
- change in, base / nucleotide, sequence (in DNA) ;
- during DNA replication ;
- base substitution ;
- often no effect / silent mutation / may code for same amino acid ;
- base addition / base deletion ;
- have great effect on phenotype ;
- frame shifts ;
- alters whole sequence of bases after mutation ;
- may lead to stop codon ;
- different / new, allele ;
- protein, different shape / different function / not made
locus
position of gene on chromosome