3.4.3 How genetic diversity arises

Question 1

What is the process of mitosis?

Answer 1

• DNA is replicated in interphase before meiosis begins.

• In the first division there is a separation of homologous chromosomes, halving the chromosome number.

• In the second division there is a separation of the sister chromatids.

• This produces four genetically different daughter cells.

Question 2

What does crossing over form?

Answer 2

Recombinant chromosomes.

Question 3

What is the name for two homologous chromosomes pairing up for crossing?

Answer 3

A bivalent.

Question 4

What is the chiasma?

Answer 4

It is a structure that forms between a pair of homologous chromosomes by crossover recombination and physically links the homologous chromosomes during meiosis.

Question 5

How does meiosis lead to genetic variation?

Answer 5

• Mutations can occur changing the base sequence leading to the formation of new alleles.

• In the first division of meiosis there is crossing over where homologous chromosomes swap DNA producing new combinations of alleles.

• Homologous chromosomes may be independently segregated in metaphase (1).

• During fertilisation there is random fusion of gametes.