Meiosis (AQA GCSE Biology)

Flashcards covering key concepts of Meiosis for AQA GCSE Biology, including definitions, processes, and importance for sexual reproduction.

What is meiosis?

A type of cell division in reproductive organs that produces gametes (sex cells) which are genetically different and have half the normal number of chromosomes (haploid).

How does meiosis differ from mitosis in terms of the cells produced?

Meiosis produces four genetically different cells. Mitosis produces two genetically identical cells.

Why must the chromosome number be halved during meiosis?

So that when gametes fuse at fertilisation, the resulting zygote has the normal full (diploid) number of chromosomes. If they didn’t halve, chromosome number would double every generation.

What is meant by “haploid” and “diploid”?

Diploid: normal body cells with two sets of chromosomes (one from each parent). Haploid: gamete cells, with only one set of chromosomes.

Give the basic outline of how meiosis works: what key steps happen.

1. Genetic material (chromosomes) is copied (as in mitosis). 2. Cell divides the first time → daughter cells that each have one of each chromosome pair. 3. Cell divides a second time → chromatids are separated, resulting in four haploid gametes.

Are you required to know all the detailed stages (prophase I, etc.) of meiosis for AQA GCSE?

No. The specification says knowledge of the stages of meiosis is not required. You need to understand the overall process: halving chromosome number, making four genetically different gametes, and why it's needed.

What does “genetically different” mean in the context of meiosis? Why does variation happen?

Because chromosomes are shuffled: each gamete gets different combinations of maternal and paternal chromosomes. This mixing, plus random fertilisation, means offspring are not identical.

What are gametes? Give examples.

Gametes are sex cells produced by meiosis. Examples: In animals: sperm and egg cells. In plants: pollen and egg cells (ovum).

What happens at fertilisation?

Gametes (one from each parent) fuse → form a zygote with the full (diploid) number of chromosomes. The zygote then divides by mitosis for growth and development.

Why is meiosis important for sexual reproduction?

Produces genetic variation among offspring, which is advantageous especially if the environment changes. Ensures chromosome number stays stable from generation to generation via halving and then restoring.