Genetic information, variation and relationships between organisms

Question 1

2 marks

Explain a mutation, which involved the addition of one nucleotide within a sequence

Answer 1

1. Frameshift / all triplets moved
2. So affects more than one amino acid

Question 2

2 marks

Describe how a phosphodiester bond is formed between two nucleotides within a DNA molecule.

Answer 2

1. Condensation reaction–> loss of water
2. Between phosphate and deoxyribose
3. Catalysed by DNA polymerase

Question 3

4 marks

Explain how mutation can result in production of a non-functional protein receptor

Answer 3

1. Change in DNA base- mutation changes triplet/ causes frameshift
2. Change in amino acid sequence
3. Alter position of hydrogen/ionic/disulfide bonds
4. Change in tertiary strucure

Question 4

4 marks

Use your knowledge of natural selection to explain why resistance is so common in Africa

Answer 4

1. Random genetic mutation for allele for the resistance
2. This beneficial allele leads to survival of the fittest and they are more likely to survive
3. They breed and pass on the allele
4. Allele frequency increases over many generations

Question 5

5 marks

Natural selection

Answer 5

1. Variation happens when new alleles are generated by random genetic mutations
2. A new selection pressure of a predator creates a struggle for survival
3. Those will beneficial alleles are best adapted to selection pressure and survive
4. They breed and pass on these beneficial alleles
5. Next generation will have a higher fequency if beneficial alleles in gene pool

Question 6

Explain antibiotic resistance

Answer 6

1. Frequent use of antibiotic creates selection pressure
2. Bacteria with mutation are more likely to survive
3. Reproduce more than other types ad pass of beneficial allele to offspring
4. Frequency of beneficial allele increases in subsequent generations
5. Frequency of resistant types increases in subsequent generations

Question 7

4 marks

Desrcibe aseptic tecnhiques

Answer 7

1. Disinfect surface prior to the investigation
2. Use a sterile spreader
3. Have a bunsen burner close to work space to create convection current to remove microoraginism upwards
4. Flaming neck of the bottle
5. Slightly lifiting lid of algar plate to avoid contiminates getting in

Question 8

One farmer stated that the increase in the use of Bt crop plants had caused a mutation
in one of the insect species to become resistant to the toxins in the plants and that this mutation had spread to other species of insect. Was he correct? Explain your answer.

Answer 8

1. Mutations are spontaneous/random;
2. Only the rate of mutation is affected by environment;
3. Different species do not interbreed/do not produce fertile offspring;
4. So mutation/gene/allele cannot be passed from one species to another;

Question 9

5 marks

Haemoglobins are chemically similar molecules found box in many different species.
Differences in the primary structure of haemoglobin molecules can provide evidence of phylogenetic (evolutionary) relationships between species.
Explain how.

Answer 9

1. Mutations change bases
2. Change in amino acid sequence
3. Mutations build up over time
4. More mutations =more differences in amino acid sequence between distantly related species;
5. Distantly related species have earlier common ancestor

Question 10

4 marks

Define ‘gene mutation’ and explain how a gene mutation can have:
* no effect on an individual
* a positive effect on an individual.

Answer 10

1. Gene mutation is the change in the base sequence of DNA
2. Results in the formation of a new allele
   No effect:
3. Genetic code is degenerate so aa sequence may not change
4. Does change aa sequence but no effect on tertiary structure
5. New allele is recessive so doesnt influence phenotype
   Positive effect:
6. Results in change in polypeptide that positively changes the properties of the protein
7. May result in increased reproductive success

Question 11

2 marks

Farmers are now being encouraged to replant hedges on their land. Suggest and explain one advantage and one disadvantage to a farmer of replanting hedges on her farmland.

Answer 11

Advantage -
1. Greater biodiversity so increase in predators of pests
2. Increase in pollinators so more yield/income
3. May attract more tourists/subsidies to their farm so more income from diversification
Disadvantage -
2. Reduced land area for crop growth/income
3. Increase pest population so less yield/less income/more need for pesticides
4. Increased interspecific competition so less yield/income
5. More difficult to farm so less income