Topic 4: meiosis

Question 1

describe how genetic variation is introduced during meiosis:

Answer 1

Genetic variation can be introduced in a variety of ways such as during meiosis cell division, mutations and the random fertilisation of gametes.

Meiosis cell division creates genetically different gametes. Unlike in mitosis, there are two nuclear divisions in this process which results in four haploid daughter cells.

Question 2

Define haploid

Answer 2

one copy of each chromosome

Question 3

Define diploid

Answer 3

two copies of each chromosome

Question 4

The genetic differences are introduced by two key processes in meiosis. Name these key processes

Answer 4

Independent segregation Crossing over

Question 5

Describe how crossing over introduces variation (include a diagram to demonstrate a chiasma).

Answer 5

Crossing over occurs in meiosis I. When homologous pairs line up opposite each other at the equator in meiosis 1, parts of the chromatids can become twisted around each other.

This puts tension on the chromatids, causing pairs of the chromatid to break.

The broken parts of the chromatid recombine with another chromatid (genetic recombination).
This results in new combinations of alleles in the gametes.

Question 6

Use your knowledge to describe how independent segregation introduces variation.

Answer 6

In meiosis I, homologous pairs of chromosomes line up opposite each other at the equator of the cell. It is random which side of the equator the paternal and maternal chromosomes from each homologous pair lie.
These pairs are separated, so one of each homologous pair ends up in the daughter cell.
This creates a large number of possible combinations of chromosomes in the daughter cells produced.