Topic 4 - Mutations & Meiosis

Question 1

Define the term mutagenic agent.

Answer 1

A factor that increases the rate of mutation.

Question 2

What type of mutation doubles the number of chromosomes and explanation?

Answer 2

• Non-Disjunction
• in meiosis chromosomes not separated (hence DNA seeming doubled)

Question 3

Apart from mutation explain one way genetic variation within a species is increased?

Answer 3

• Random fertilisation of gametes
• produces new allele combos

Question 4

Why are (named animal) eggs produced by meiosis genetically different?

Answer 4

Due to crossing over and independent segregation

Question 5

Define the term ‘gene mutation’ and explain how a gene mutation can have:
- no effect on an individual
- a positive effect on an individual

Answer 5

• Gene mutation = change in base seq of DNA, results in formation of new allele
  No effect
• genetic code = degenerate so AA seq may not change
• does change AA but no effect on tertiary structure
  Positive effect
• results in change of pp that positively changes properties of protein
• may result in inc reproductive success

Question 6

What are two differences between mitosis and meiosis?

Answer 6

• Mitosis only undergoes 1 division, whereas meiosis has 2 rounds of division.
• Mitosis forms 2 daughter cells that are genetically identical, meiosis forms 4 non-genetically identical daughter cells.

Question 7

From the results what can you conclude about the movement of chromosomes in meiosis in this named species?

Answer 7

• did separation of homologous chromosomes occur
• did crossing over occur
• are either of these rare

Question 8

Why might a change at AA 300 had no effect on rate of reaction catalysed by enzyme but same change at AA 279 significantly reduced rate of reaction catalysed by enzyme?

Answer 8

• both - charged to + charged change in AA
• change at AA 300 does not change shape of AS
• AA 279 may have been involved in ionic bond so shape of AS changes.

Question 9

Explain how the chromosome no. is halved during meiosis.

Answer 9

• one of each chromosome from each homologous pair
• goes to each daughter cell

Question 10

Describe the process of crossing over and explain how it inc genetic diversity.

Answer 10

• homologous pairs of chromosomes associate
• chiasma forms
• equal lengths of chromatids exchange
• producing new combos of alleles

Question 11

How is a third copy of a chromosome in a person produced?

Answer 11

• in meiosis
• the homologous pairs of chromosomes did not seperate
• so resulted in an extra copy of the chromosome

Question 12

Explain why all cells of body may have a mutation.

Answer 12

• mutation occurred in gamete
• all cells derived from this single cel by mitosis