Blueprint For Life

Question 1

Macro-evolution vs Micro-evolution?

Answer 1

Macro-evolution: takes place over millions of years. Results not only in new species but even families and orders.

Micro-evolution: takes place over shorter periods of time and results in changes within a population, can still result in new species. New forms witbin a population are referred to as variations or races e.g. Breed of dog.

Question 2

Case study to show environmental change can lead to change in a species?

Answer 2

Peppered moth-
1) pre-industrialisation the light coloured tree trunks favoured light coloured moths for camouflage, hence they dominated the population.

2) industrialisation produces soot which stains the tree trunks. Dark moths are more suited for the changed environment as they now camouflage better, dark moth population increase and light moth pop decrease.
3) modern clean air act= decrease in soot, tree trunks made lighter again and light coloured moths dominate.

Chemical change: insecticides (cattle ticks)
Insecticides arsenic, ddt, introduced and within 15 years tick population largely resistant to it (due to natural selection)

Question 3

How is evolution supported by: palaeontology?

Example?

Answer 3

The study of fossils provides direct evidence of once living organisms and how they changed over time.
Transition fossils-intermediate form between two major types of organisms, possessing characteristics from both group.

Example- Archaeopteryx
Transition fossil between reptiles and birds- small flying dinosaur with feathers.

(Has wishbone feathers but also teeth and solid bones)

Question 4

How is evolution supported by: Biogeography?

Example?

Answer 4

Biogeography-Study of distribution of organisms. Distribution patterns provide evidence that species originated from a common ancestor but when isolated have evolved differently (due to different selective pressures).

Example- echidna
Australian and new guinean echidna are thought to come from a common ancestor when they were both part of gondwana, but since splitting have evolved differently due to different pressures.
Aussie-short beak, smaller body
New guinean-larger beak, larger body

Question 5

How is evolution supported by: comparative embryology?

Example?

Answer 5

Comparative embryology- study of embryos of different organisms, looking for similarities and differences, similarities supporting evolution as they suggest a common ancestor.

Example-
All chordates possess pharyngeal gill pouches during embryonic development even if they do not possess them later in life, suggesting common ancestor.
(E.g. Become ear, gills etc)

Question 6

How is evolution supported by: comparative anatomy?

Example?

Answer 6

Comparative anatomy- studying the structures of different organisms. Homologous structures (structures that are similar but perform different functions) suggest evolution from a common ancestor, adapting to separate selective pressures.

Example- pentadactyl limb (5 digits) and same basic bone composition present in many vertebrates but adapted to different selective pressures, performing different functions (e.g. Human arm, whale fin, bat wing) suggesting a common ancestor.

Question 7

Environmental changes effecting evolution: physical and chemical? Why does it result in competition?

What impact do these have?

Answer 7

Physical factors: temp, water availability, light, wind, slope, substrate, tides

Chemical factors: presence/absences of gases such as carbon dioxide or oxygen, pH and concentrations of salt and heavy metals

Results in competition as resources become limited and organisms will have to compete

Change of environment=selective pressure.

Organisms that have a variation that confers with the environment compete most successfully and are said to have an adaption to the environment, survive and breed, and pass on their genes.

This stable environments exert little pressure on the evolutionary process.

Question 8

Outline a first-hand investigation to model natural selection:

Answer 8

Toothpick prac:

Materials: 20 red toothpicks, 20 green toothpicks, metre ruler, stopwatch, 3 participants

1) assign 2 people the role of “predator”
2) measure out a 3m x 3m area of grass
3) have the predators look away while the other person scatters all 60 toothpicks in the area
4) give the predators 15 seconds (timed by the 3rd participant) to find and collect as many toothpicks as possible
5) repeat steps 4) 5 times

Results: green toothpicks are able to camouflage in the green grass and thus were found less often than the red toothpicks. This example in an ecosystem would mean that the red toothpicks would be easier to see therefore eaten more frequently by predators. As such the green toothpicks have a natural adaption to the environment and will survive to breed more often, over time becoming the dominant colour

Question 9

How is evolution supported by: biochemistry?

Example?

Answer 9

Similarities between organisms on a molecular level point to common ancestor therefore evolution.

Example: organic compounds like haemoglobin, RNA and hormones used to compare amino acid sequences between species. More similar = more recent common ancestor

Also an example is DNA hybridisation

Question 10

Give an example of how technology has changed scientific thinking about evolutionary relationships:

Answer 10

DNA Hybridisation:
Double stranded DNA is heated so that the base pairs are broken to form 2 single strands. A single strand from 2 different species are mixed to form a hybrid double stranded DNA and allowed to cool. The base pairs that do match will bind the strands together but due to being different species there will be mismatches in the base pairs. The fewer mismatches the more related the species.

Change in thinking: showed that human and chimpanzee DNA is 98% identical leading to suggestion humans and chimps should be in the same genus while now they are in different families.

Usually done on cytochrome which is mitochondrial dna due to low mutation rate

Question 11

Explain darwin/wallace’s theory of evolution by natural selection:

Answer 11

Erasmus darwin: evolution occurs through sexual selection and competition. Introduced concept of evolution by most suited characteristic for an environment.

Charles darwin/wallace: suggested the mechanic: natural selection

• there will be natural variations between individuals
• in the face of selective pressures, organisms with favourable variations will survive to reproduce and these variations are inherited by their offspring
• favourable characteristics become more common in the pop

When a population is isolated they evolve independently

Question 12

Divergent vs convergent evolution?

Examples?

Answer 12

Divergent- species that evolved from a common ancestor. Isolated populations subjected to different selective pressures will evolve differently. Eventually there will be enough genetic variation to inhibit interbreeding producing fertile offspring, thus new species.

Example: darwins finches
Studied finches with the same basic structure but different environments, had different shape/size beaks and body sizes to fit their environment and diet.

Convergent- similar selective pressures produce similar evolutionary responses in species that do not share a recent common ancestor.

Example: sharks and dolphins
Both have find, streamlined bodies, fins, layer of fat, diet of fish. Yet they are in entirely different orders of mammals.

Question 13

What is the Wallace line?

Answer 13

A hypothetical line that separates asian and australian fauna.

Wallace developed the theory of natural selection in this region independently of charles darwin who came to the same conclusion at the same time in Galapagos.

Question 14

Historical development of the theory of evolution and social and political influences on these developments:

Answer 14

Ray 1686- serpents heads carved on ammonites to fit legend of st hilda turning snakes to stone

Hooke 1696- found fossil-like shells to be reliable evidence of extinct organisms. Went against church doctrine that all organisms are still present from creation.

Linnaeus 1735- binomial classification system with humans and apes classified together. New species come from hybridisation but under the hand of god.

Buffon 1749- suggested life older than 6000 years. Modern definition of species. Believed in evolution but thought environment was the direct agent of change.

Erasmus Darwin 1794- one of the first theories of evolution. All life developed from a single ancestor. Did not know mechanism (natural selection)

Lamarck 1809- though species do not become extinct just evolve into a new species. Believed in the notion of inherited characteristics (like if you lose an arm your kid has no arm)

Wallace and darwin: obvious

Question 15

Outline the experiments carried out by mendel:

Answer 15

Worked with the garden pea plant to study inheritance. He selected a variety of characteristics in the plants which only had 2 forms e.g. Short and tall. He then procured pure breeding plants of each form of each characteristic e.g. Tall pea plants that only produce tall offspring and vice versa for short, to form his parent generation.

Mendel first cross-fertilised two true-breeding plants for one characteristic (e.g. Tall with a short), to form his F1 generation.

The F1 generation was then allowed to self fertilise or cross-fertilise with each other to produce the F2 generation.

Results:

• F1 generation all one phenotype (e.g. All tall)
• F2 generation have a 3:1 ratio of phenotypes (e.g. 3 tall: 1 short)

Repeated this with all characteristics

Conclusions:
-there is no blending
-inheritance is controlled by a pair of factors (he named factors)
-these factors are separated from one another when the sex cell forms (law of segregation)
-characters are either dominant or recessive
Only the dominant factor appears in F1, dominates in F2 in a ratio of 3:1.

Also experimented with 2 traits at a time and determined they were inherited independently (law of independent assortment) (only works if the genes coding for these traits are on different chromosomes)
(Dihybrid cross=9:3:3:1)

Question 16

Experimental techniques used by mendel that lead to his success?

Answer 16

• used peas, which produce successive generations rapidly and whose pollination can be controlled.
• selected easily observable characteristics with two easily identified phenotypes
• only studied one characteristic at a time
• high level of repetition over long period of time= reliable
• bred a single variety for two years to ensure parent generation was pure breeding
• kept meticulous records

Question 17

What is a gene?

Allele?

Answer 17

Genes are sections of DNA which codes for proteins and expresses itself as a phenotype
(Exons, introns do not code for proteins)

Allele= an alternate form of a particular gene

Question 18

Pedigree chart symbols?

Answer 18

Male=square
Female=circle
Coloured in=affected
Horizontal line=mating
Square fork= offspring
Triangular fork= twins
Line between triangular fork= identical twins

Question 19

Homozygous vs heterozygous?

Answer 19

Homozygous: both alleles for the characteristic are the same (e.g. TT or tt)

Heterozygous: alleles for the characteristic are different (e.g. Tt)

Question 20

Phenotype vs genotype?

Answer 20

Phenotype= appearance of the characteristic.

Genotype=actual alleles present in the organism

Question 21

Explain the relationship between dominant and recessive genes and phenotype?

Answer 21

An organism with a homozygous dominant genotype or heterozygous genotype will have dominant form of the characteristic expressed as the phenotype.
The recessive gene is only expressed if the genotype is homozygous recessive.

Question 22

Why was mendels work not recognised in his time?

Answer 22

• his use of statistical analysis was considered radical in biology, not well understood
• was not a high profile scientist
• paper neither presented well or to an influential group of scientists
• idea that inheritance came from discrete units was not understood in a tome when chromosomes and cells were only first being understood.

Question 23

Explain the purpose of hybridisation within a species:

Example?

Answer 23

Hybridisation within a species-crossing of different varieties of one species to produce new varieties with different combinations of characteristics.

Systematic crosses between different varieties of one species to form hybrids that have new combinations of desirable characters.

Example: sheep
Border leicester rams are crossed with merino ewes to produce “first cross mothers” which are well proportioned, highly fertile, good at foraging and good milk production.

Question 24

Role of Sutton and Boveri in identifying the importance of chromosomes?

Answer 24

Boveri and Sutton proposed that chromosomes bear hereditary factors in accordance with mendelian laws.

Boveri:

• chromosomes remain organised units during cell division
• (most importantly) sperm and eggs each contribute the same number of chromosomes to a zygote

Experiment: using sea urchins, fertilised an egg with 2 sperm cells to produce daughter cells with variable number of chromosomes. These daughter cells only survived if they had a full set of chromosomes present. He concluded:

• that a specific assortment of chromosomes is responsible for normal development
• since there are far less chromosomes than inherited characteristics, each chromosome carries many factors.

Sutton:
By studying meiosis in grasshoppers found:
- meiosis is a reduction division and full number of chromosomes restored to make the zygote
- chromosomes occur in distinct pairs (one of each pair paternal and maternal (homologous pairs))

Concluded:

• chromosomes are units of inheritance
• if 2 characteristics are on the same chromosome they will move together

Question 25

What is a chromosome?

Answer 25

DNA wrapped around a protein core.

Question 26

C? G? A? T? U?

These are ____?

Convert to mrna: CATGCCGTA

Answer 26

Cytosine
Guanine
Adenine
Thymine
Uracil

These are bases

CATGCCGTA = GUACGGCAU

Combos: C-G (3 hydrogen bonds)
A-T(or U) (2 hydrogen bonds)

Question 27

What is DNA?

What is a nucleotide?

Answer 27

A nucleic acid. A double stranded helical molecule with each strand comprised of nucleotides connected to a complementary strand by pairing of bases, A-T & C-G

Nucleotide= a sugar, a phosphate and a base. The sugar and phosphate make up the “backbone” of the DNA molecule.

Question 28

Meiosis?

Answer 28

Interphase: cell does cell things, DNA replicated so all 46 chromosomes exist as a duplicated sister chromatid.

Prophase I:

• chromosomes condense, centrioles duplicate and nuclear envelope breaks down (just like mitosis)
• homologues (homologous pairs) come together lengthwise
• while they are together crossing over occurs: sections if the chromosomes being exchanged

Metaphase I:
-homologues line up at the equator of the cell still paired up (i.e. Not a single file line)

Anaphase I:
-homologous pairs separated and pulled to opposite sides of the cell via microtubules from the centrioles

Telophase I:
-cell separates via cytokinesis, homologues now in separate cells

No interphase II and hence no DNA replication

Prophase II:
- chromosomes condense, centrioles duplicate and nuclear envelope breaks down

Metaphase II:
-chromosomes line up at the equation in single file

Anaphase II:
-sister chromatids separated and pulled to each end of the cell

Telophase II:
-cell splits via cytokinesis, overall leaving 4 cells with 1 copy of each the 23 chromosomes (i.e. 4 haploid cells)

Question 29

Relationship between structure and function of chromosomes during meiosis and inheritance of genes?

Answer 29

• genes are carried on chromosomes
• during meiosis chromosomes replicate and the haploid gametes are given one of two possible chromosomes.
• law of independent assortment: when pairs of factors segregate, they do so independently of other factors i.e. Are distributed into gametes independently of other pairs of factors (except when genes situate on the same chromosome)

Question 30

Model if meiosis including crossing over, segregation and production of gametes:

Answer 30

Do it in class

Question 31

Role of gamete formation and sexual reproduction in variability of offspring?

Answer 31

Sexual reproduction- joining of a male and female gamete in a combination of genes which is different from the mother and father.

Gamete formation- random assortment of chromosomes (law of independent assortment)
-crossing over: the exchange of genes between chromosome pairs. Causes the combination to alleles on the chromosomes in the gametes to be different from the alleles of the chromosomes of the parents.

Question 32

What is sex linked inheritance?

Answer 32

The expression of an allele related to the chromosomal sex of the individual in the phenotype.

Sex-linked traits do not have simple mendelian ratios as the probability of displaying the characteristic is different for males and females. As men only have one pf each sex chromosome if they carry a recessive gene on either itll be displayed. Women need to have a homozygous recessive gene on the x chromosome for it to be displayed.

Question 33

Incomplete dominance and codominance?

Why dont simple mendelian ratios work?

Answer 33

Incomplete dominance- one allele is not completely dominant over the other and thus heterozygous offspring are a “blend” of their parents.
Snapdragon flower: white and purple

Codominance- both alleles are expressed but the characteristics are independent of each other.
E.g. Roam cows

Question 34

Describe the work of Morgan identifying sex linkage:

Answer 34

Worked on drosophila flies showing mendelian ratios of red/white eye colour.

Crossed a red eyed female with a white eyed male (i.e. XRXR and XrY)
The result being 100% red eyes.

He then cross bred the F1 generation (i.e. XRXr and XRY)
And found 100% females red eyes and males 50% of each (1:1)
I.e. Not fitting mendelian 3:1 ratio

Thus hypothesised that the gene for eye colour for the drosophila fly must be carried on the X chromosome and the Y chromosome has no gene for eye colour. Later found to be right.

Question 35

How can the environment effect the expression of a gene in an individual?

Answer 35

Environment includes factors that act upon the organism such as temp, pH and nutrition. These effect the expression of the gene in an individual and thus identical inherited characteristics do not always result in identical organisms.

Question 36

Experiment to demonstrate the effect of the environment on phenotype

Answer 36

Effect of soil pH on hydrangeas flower colour:

Materials- 50 similar size hydrangeas, garden bed, limestone, sulphur, string

Method- 1) section the garden bed off using string into 10 1m^2 areas

2) use limestone and sulphur accordingly to either lower or raise pH of each 1m^2 section so every 0.2pH increment between pH 5 and pH 7 is present.
3) plant 5 hydrangeas in each section
4) expose hydrangeas to similar conditions of temp, sunlight, water etc. until change of flower colour is observed

Result:
6ish range gives pink colour, 5ish range gives blue colour

Question 37

DNA replication: process and significance

Answer 37

Process:

• begins at a certain sequence of bases
• enzyme helicase attaches and unwinds (“unzips”) the dna strands by breaking hydrogen bonds (creating the replication fork).
• enzyme DNA polymerase comes in and adds free nucleotides in the 5’ to free prime direction.
• This allows DNA polymerase to work continuously on the leading strand as it runs 5’ to 3’ (towards the fork).
• The lagging strand however runs 3’ to 5’ and thus completely in small fragments working backwards so it can work 5’ to 3’.
• the new DNA molecules are rewound into a double helix by the enzyme DNA ligase.

Fragments are called okazaki fragments, gaps left in then filled up by ligase

Significance:
DNA replication produces 2 exact copies of the original DNA molecule meaning that in mitosis the 2 daughter cells can be identical and exact copies of the parent cell and thus perform the same functions.

DNA polymerase needs a rna primer made by primase (not assessable)

Question 38

Production of polypeptides/protein synthesis:

Step 1: Transcription

Answer 38

• Occurs inside the nucleus of the cell
• DNA molecule unwinds at a specific sit which codes for the production of a specific polypeptide
• nucleotides align with complementary bases on one side of the DNA molecule and RNA polymerase helps the nucleotides join together to form a strand of mRNA (T’s replaced with U’s)
• mRNA then exits into the cytoplasm

Question 39

Production of Polypeptides/protein synthesis:

Step 2: Translation

Answer 39

-Occurs outside the nucleus

-mRNA binds with a ribosome at the start codon, forming a template for polypeptide production.
Each group of 3 bases (codon) codes for a specific amino acid.

• tRNA (transfer RNA) consist of an anti-codon and an amino acid. As the mRNA moves through the ribosome a tRNA with the anti-codon to match the frontmost codon will temporarily bind to the mRNA.
• The frontmost amino acid binds to the backmost one and the frontmost tRNA (now without an amino acid) is released.
• The process stops when a stop codon is reached and the polypeptide chain is released into the cytoplasm.

Question 40

Difference between peptide and polypeptide?

Answer 40

Peptide= sequence of less than 50 amino acids

Polypeptide= 50 or more amino acids

Question 41

Relationship between proteins and polypeptides?

Answer 41

A protein can be formed from one or several polypeptides linked together and folded into a 3d shape.

(A polypeptide is a chain of amino acids held together by peptide bonds)

Question 42

Beadle and Tatum’s experiment?

Answer 42

Experiment using red bread mould:
-knew that the mould had the enzymes to convert sugars and salts into amino acids and vitamins it needs for growth, such as vitamin B4 and B1 under normal conditions.

• exposed the mould to x-rays to induce genetic mutations, some disrupted the mould’s ability to make certain nutrients, and this grow.
• added supplements to the growth medium 1 by 1 to find which supplement would make it start growing and this which enzyme it was missing.
• breeding the mutant strains with normal ones showed the defects were recessive traits, proving the genes were altered.

Thus tatum and beadle formed their hypothesis: one gene = one protein.
This is true for simple organisms but other animals like humans many proteins are constructed from multiple polypeptide chains combined to make one protein.

Thus the new hypothesis now reads “one gene = one polypeptide”

Question 43

Explain how mutation in DNA lead to new alleles?

Answer 43

Mutation- a change in the amount or structure of DNA in an organism which can result in a change in the characteristics of an organism.

• mutations my affect a gene (genic), part of or a whole chromosome
• mutations that occur in sex cells can generate new alleles which are passed to the next generation. Mutation in somatic cells will not be passed to the next generation.

Question 44

Types of Genic Mutation:

9 types

Answer 44

Deletion- a base is lost/deleted

Insertion- an extra base is added/inserted

Frameshift- the reading “frame” changes, thus changing the amino acid sequence from that point forward.
-deletion and insertion can cause a frameshift

Substitution mutation- one base is substitutes for another:

• missense: if the substitution changes the amino acid
• silent: when the substitution does not change the amino acid
• nonsense: when the substitution changes the amino acid to a “stop”

Premature stop-the mutation codes for a stop codon. May be caused by a substitution mutation or a frameshift mutation

Duplication- part of a gene is repeated as an extra copy

Inversion- DNA sequence breaks off and reattaches backwards

Translocation- part of DNA from one chromosome attaches to another

Amplification- many extra copies if a DNA sequence are found in the chromosome

Question 45

Chromosomal mutations:

Answer 45

Aneuploidy: An abnormal chromosome number is present in the organisms.

• Occurs when chromosomes fail to separate during meiosis (non-disjunction).
• results in one haploid cell with one less chromosome and one with an extra chromosome.

Polyploidy: multiples of the full of chromosomes are present in the organism (3n, 4n etc (most organisms have 2n))

• occurs if the chromosomes fail to separate during mitosis, leaving a cell with 4n sets of chromosomes.
• offspring is a polyploid, common in plants.

Question 46

Construct a flow chart that shows changes in DNA sequences can result in changes in cell activity:

Answer 46

Normal cell:
DNA-    TAC ACG TTG AGC
mRNA- AUG UGC AAC UCG
tRNA-   UAC ACG UUG AGC
polypeptide- correct and functional

Mutated Cell (deletion of 1st A)
   DNA- TCA CGT TGA GC
mRNA- AGU GCA ACU CG
  tRNA- UCA CGU UGA GC
polypeptide- incorrect and dysfunctional

Question 47

Types of mutagenic radiation:

Examples of its effects?

Answer 47

Types of mutagenic radiation:

Ionising radiation- such as x-rays and gamma rays
-can penetrate cells and tissue where it imparts energy to a neutral atom causing an electron to be knocked out of its orbit. This creates a free radical which reacts violently with other molecules like DNA causing mutations such as deletion, substitution etc

UV radiation-

• mainly absorbed by pyrimidine bases (cytosine, thymine, uracil).
• can cause a bond to form between 2 of the same pyrimidine base that happen to already be adjacent, blocking normal duplication of DNA.

Evidence:

• survivors at Hiroshima and Nagasaki given large doses of radiation, their descendants suffered damage to their DNA e.g. Leukemia
• Liquidators after Chernobyl exposed to more than a lifetime’s dose of radiation in 60s. Study many years later showed severe chromosomal abnormalities e.g. Multiple centromeres, random fragmentation.

Question 48

How has understanding the source of variation (which is?) supports Darwin’s theory of evolution by natural selection?

Answer 48

Current understanding of genetics shows variation can occur by:

• random joining of gametes to form a zygote (random fertilisation)
• crossing over during mitosis
• random segregation of chromosomes (law of independent assortment)
• mutations of chromosomes and genes

Darwin’s theory of natural selection requires 2 aspects, variation in a species and an environmental pressure. While environmental pressure was clearly explained, the mechanism for variation was then unknown. Thus knowing one now supports the theory.

Question 49

Explain a modern example of natural selection:

Answer 49

Antibiotic resistance in bacteria:
-within a bacteria population a low frequency of bacteria are/may be resistant to a certain antibiotic.

• when the antibiotic is introduced into the population’s environment an environmental pressure is created.
• The bacteria that survive and are able to reproduce will mostly be bacteria which display resistance to the antibiotic.
• they reproduce and pass their resistance to their offspring and up the frequency of resistant bacteria within a population increases as a result.
• after subsequent treatments all non-resistant bacteria are wiped out and the whole population is now resistant.

Question 50

What is punctuated evolution?

How does it differ from the process proposed by Darwin?

Answer 50

Darwin proposed that evolution was a slow gradual process.

Punctuated equilibrium proposes that short rapid periods of evolution due to evolutionary pressures are followed by long periods of evolutionary stability where there is little change to a species.

This theory is supported by the fossil record which documents periods of mass extinctions and rapid changes.

Proposed in 1972

Question 51

Watson, Crick, Franklin and Wilkins:

Answer 51

Watson and Crick: created the model of DNA
-suggested helical structure of DNA
-gathered the data that # of adenine= # of thymine and # of cytosine= # of guanine.
Chargaff then interpreted this as pyrimidine and purine bases pairing up in DNA

Franklin: information used to make this model came largely from franklin

• used x-ray crystallography on fibres of DNA resulting in images like photo 51 showing the helical nature.
• died early due to ovarian cancer (probs due to xrays) before the nobel prize was awarded (probs sexism involved too)

Wilkins:

• provided franklin with DNA fibres
• obtained photo 51 from franklin without her permission and gave it to watson and crick.

Question 52

Method used in cloning organisms:

Answer 52

1) haploid ovum has its nucleus removed
2) nucleus of a diploid donor cell (i.e. Body cell) is fused with ovum to form an embryo
3) embryo implanted in surrogate mother

Question 53

Identify how reproductive techniques may alter the genetics of a population:

• artificial insemination
• artificial pollination
• cloning

Answer 53

Artificial insemination:
Process of fertilisation without intercourse.
Involves either-
-injecting sperm into the vagina
Or
-forming embryos using IVF and implanted the fertilised egg into the uterus.

Used in agriculture so a stud can pass its characteristics to offspring around the world.

Artificial Pollination:
Manually transferring pollen of a plant to the female stigma of another flower.
Allows single plant to have large number of offspring and thus pass on favourable characteristics.

Cloning:
(Technique covered later)
Produces a clone genetically identical to the organism whose diploid nucleus was used to create it.
+precise control of characteristics of organisms
-genetically identical population=extremely susceptible to environmental pressures.

First 2 techniques increase genetic diversity but may impede natural selection as couples who could not breed can and pass on these characteristics.

Question 54

Transgenic species:
How to produce one?
Example?
Ethical issues?

Answer 54

Transgenic species-contains DNA from other species to improve the organism’s characteristics.

Creation:
1)identify useful gene and the chromosome its on. Gene is then isolated and cut out using special restrictive enzymes (gene shears) which cut at a particular base sequence.

2) regulatory genes added to ensure the DNA functions.
3) gene may be copied several tomes (amplification)
4) gene is inserted into the DNA of another organism via bacteriophage, microinjection, particle gun or other method. DNA ligases help new DNA fragments to seal and strengthen their bonds.

Examples:

• trout gene for frost resistance put in strawberries
• bGH (bovine growth hormone) put in salmon creating larger faster salmon.
• Bt cotton has gene from (bacillius thuringiensis) bacteria which produce Bt toxin, increases plants resistance to pests.

Ethical Issues:

• safety of transgenic species as food
• effect of transgenic species on ecosystems as can reduce genetic variability=susceptible to environmental pressures
• detrimental effect of foreign gene on the species e.g. Transgenic pigs are plagued with arthritis
• tampering with nature for commercial gain
• may interfere with evolution

+can help in the treatment of disease and improve food production efficiency, getting food to impoverished areas.

Question 55

Plant and Animal example of reproductive technology reducing genetic diversity:

Answer 55

Bt cotton- transgenic species that produce a toxin to reduce attacks from pests and need for pesticides. If Bt crops became the standard crop all other varieties would be lost and the species will become vulnerable to environmental pressures.

Transgenic salmon- bGH salmon are bigger and faster than other salmon. Would out compete other species in the wild as well as other salmon variations, potentially wiping out other fish populations and reducing genetic variability in salmon.

Question 56

Effect of reproductive technologies on genetic variability:

Answer 56

Speed up introduction of favourable characteristics into a population but reduce genetic variety in the process.

Question 57

Social and political effects on research in evolution:

Answer 57

For darwin:

Social- Lack of formal widespread education needed to understand and recognise his work

Political- church wasn’t separated from the state at the time and the theory of evolution conflicted with the creationist story e.g. The world is only 4000 years old and all species from creation are still present