Meiosis - Grosse Pointe Public Schools...Definition Meiosis is a process that produces new cells with half the usual number of chromosomes. New cells are called sex cells – Gametes

Meiosis

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Definition

Meiosis is a process that produces new cells with half the usual number of chromosomes.

New cells are called sex cells– Gametes (sperm and egg cells)

Sex Cells Sex cells have

only 1/2 the number of chromosomes. 1 chromosome from each pair.

Human body cells have 46 chromosomes (23 pairs). The chromosomes in each pair are called homologous. Homologous chromosomes are usually the same size and shape.

Homologous Chromosomes

Each pair contains 1 chromosome donated by the mother and one donated by the father.

Homologues Share Genes

A homologous pair of chromosomes contain all of the same genes.– Homologous pairs may contain

different versions of genes called alleles.

Why is it important that sex cells have half the usual

number of chromosomes?

When two gametes fuse, each parent donates 1/2 of a homologous pair of chromosomes.

offspring will receive a normal number of chromosomes in each body cell. Half from each parent.

Meiosis is cell division similar to Mitosis. In mitosis, chromosomes are copied once, then the nucleus divides once.

In Meiosis the chromosomes are copied once, then the nucleus divides twice.

Homologues are

During Meiosis, one of each chromosome pair (homologues) ends up in a sex cell.

What is the function (purpose) of meiosis?