4.3 - Mutations and meiosis

Question 1

What is an allele?

Answer 1

alternative version of the same gene

Question 2

What is a genetic mutation?

Answer 2

change in chromosome base sequence which results in the formation of a new allele

Question 3

What is a mutagenic agent?

Answer 3

factor that increases the rate of gene mutation

Question 4

Describe the no. of nuclear divisions, the parent cell, and the daughter cells produced in meiosis

Answer 4

• 2 nuclear divisions
• single diploid parent cell produces 4 genetically different haploid daughter cells (gametes)

Question 5

How are genetically different daughter cells produced during meiosis?

Answer 5

independent segregation of homologous chromosomes

Question 6

How can chromosome mutations spontaneously arise during meiosis?

Answer 6

• non-disjunction: failure of homologous chromosomes to separate
• polyploidy: an individual has more than 2 sets of chromosomes

Question 7

How does genetic variation occur, and how is it further increased in meiosis?

Answer 7

• random fertilisation of haploid gametes producing new allele combinations
• crossing over between homologous chromosomes

Question 8

Give the 6 types of mutation

Answer 8

base:
- deletion
- addition
- substitution
- inversion
- duplication
- translocation

Question 9

What is crossing over?

Answer 9

the exchange between of genetic material between 2 homologous chromosomes resulting in a new combination of alleles (occurs in meiosis 1)

Question 10

Describe what happens in meiosis 1 and meiosis 2

Answer 10

1:
- homologous chromosomes pair up
- crossing over at the chiasmata (crossing points) may occur
- cell divides + each daughter cell contains 1 chromosome from each homologous pair

2:
- chromatids of each chromosome are separated producing 4 haploid daughter cells