4.3 Meiosis and Mutations

Question 1

Explain how crossing over results in variation.

Answer 1

Crossing over- during Meiosis 1, bits of chromatids swap over to contain the same genes but different sections of alleles

Question 2

Explain how independent segregation results in variation

Answer 2

Independant segregation of homologous chromosomes, random process of which chromosomes from each parent separate into which daughter cell (one from mother one from father)

Question 3

Explain how random combination leads to variation in meiosis

Answer 3

random process in which gametes combine to form a zygote

Question 4

Summarise the process of meiosis 1

Answer 4

meiosis 1
- homologous chromosomes pair up
-chromatids cross over- to contain different alleles
- One chromosome from each homologous pair ends up in each cell

Question 5

Summarise the process meiosis 2

Answer 5

Meiosis 2
-sister chromatids separate to opposite sides of the cell by microtubules and the production of 4 daughter cells
-

Question 6

What happens in prophase 1?

Answer 6

chromatin condenses into chromosomes
homologous chromosomes pair up to form homologous chromosome pairs
Separates homologous chromosomes

Question 7

What happens in metaphase 1?

Answer 7

Homologous chromosome pairs line up along centre of the cell and microtubules attach

Question 8

What happens in anaphase 1?

Answer 8

Microtubules seperate homologous chromosome pairs

Question 9

What happens in telephase 1?

Answer 9

The nuclear envelope reappears, two cells are formed

Question 10

What is the difference between meiosis 1 and meiosis 2?

Answer 10

The first division of meiosis, which reduces the number of chromosomes in a cell by half. results in 2 daughter cells with half the number of chromosomes.

meiosis 2- pair of sister chromatids separated. 4 haploid cells produced

Question 11

How can you calculate the number of different zygotes with different paternal and maternal chromosome combinations?

Answer 11

2^n where n is the number of chromosome pairs

Question 12

How can you calculate the number of different gametes with different paternal and maternal chromosome combinations?

Question 13

Describe what. a mutagenic agent is and identify some possible mutagenic agents?

Answer 13

Increases chances of mutation such as UV light and viruses

Question 14

What is a non-disjunction effect and how does it occur?

Answer 14

chromosomes fail to separate, occurs in prophase 1