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Bioscience in brief

An introduction to genes and crops

How are chromosomes inherited?

Most adult cells contain two sets of chromosomes. However, sexual cells (sperm cells from the father and egg
cells from the mother) contain a single chromosome set. During reproduction, each parent contributes one set of chromosomes to their offspring.

Sexual reproduction involves the fusion of a female and a male reproductive cell (also called gametes; in humans these are the sperm and egg cells). Reproductive cells contain half the set of chromosomes from the rest of the
cells of the body. The fertilised egg therefore received one chromosome in the pair from the mother, and one from
the father.

The illustration  below shows a photograph of the  human chromosomes when viewed with a microscope (this is called a karyotype). We have 22 pairs of chromosomes, plus the sexual chromosomes Y and X. Each parent contributed one chromosome in each pair.