Meiosis is a type of cell division with two divisions that produces four haploid cells. The cells are genetically different from each other and from the parent cell.

What are homologous chromosomes?

Homologous chromosomes are a pair of chromosomes, one maternal and one paternal, with the same genes at the same loci. The alleles carried at each locus may differ.

What happens to homologous chromosomes in the first division of meiosis?

Homologous chromosomes pair up and line up at the equator of the cell. The pairs then separate, one chromosome of each pair moving to each pole.

What separates in the second division of meiosis?

The sister chromatids of each chromosome separate in the second division. Four haploid cells result from the two divisions.

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Genetics, Stem Cell Research and Cloning

Meiosis and genetic variation

3 things to know
A2 5

Overview

Haploid gametes, homologous chromosomes, the two divisions of meiosis, independent segregation with worked combinations, crossing over and recombination, meiosis against mitosis and non-disjunction.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What is meiosis?

Key term

Why is it important that gametes are haploid?

Key term

State the diploid and haploid chromosome numbers of a human.

Questions from this subtopic

Each one with the model answer underneath.

1
What is meiosis?
Model answer
Meiosis is a type of cell division with two divisions that produces four haploid cells. The cells are genetically different from each other and from the parent cell.
2
Why is it important that gametes are haploid?
Model answer
Fertilisation fuses two gametes, restoring the diploid number in the zygote. Chromosome number therefore stays constant from one generation to the next.
3
State the diploid and haploid chromosome numbers of a human.
Model answer
Human body cells are diploid, with 46 chromosomes in 23 pairs. Human gametes are haploid, with 23 chromosomes.
4
What are homologous chromosomes?
Model answer
Homologous chromosomes are a pair of chromosomes, one maternal and one paternal, with the same genes at the same loci. The alleles carried at each locus may differ.
5
What happens to homologous chromosomes in the first division of meiosis?
Model answer
Homologous chromosomes pair up and line up at the equator of the cell. The pairs then separate, one chromosome of each pair moving to each pole.
6
What separates in the second division of meiosis?
Model answer
The sister chromatids of each chromosome separate in the second division. Four haploid cells result from the two divisions.

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