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Human chromosomes

The genetic material in a human body cell lies in 23 pairs of chromosomes, 46 in all. One chromosome in each pair comes from the mother and one from the father. Sex cells are made by meiosis and have only one set, 23 chromosomes, so the child again gets 46 when egg and sperm fuse. Mitosis, used for growth and repair, gives two cells that each have the same 46. Bacteria are prokaryotic and do not have this nucleus. Their DNA lies free in the cell.

46=23⋅246 = 23 \cdot 2body cell, two sets
23=46/223 = 46/2sex cell, one set

Symbols

2323number of pairs in a body cell
4646chromosomes in a body cell

Example

A body cell: 23⋅2=4623 \cdot 2 = 46 chromosomes.

A sex cell: 46/2=2346/2 = 23 chromosomes.

Mitosis does not change the chromosome number. Meiosis halves it.
Practise the cell for free →

The cell membrane →

Part of Biology 1: The cell.