Mitosis and Meiosis Side by Side

0:00Your cells divide in two ways: mitosis and meiosis. Let's run them side by side.

0:07Both start with a cell with four chromosomes, strands of DNA that carry genes.

0:13They come in matching pairs: one from the mother and one from the father.

0:19First, each chromosome is copied, and the two copies stay joined.

0:24In mitosis, the chromosomes line up one by one across the middle.

0:30The copies are pulled apart and the cell splits: one division, two cells.

0:36In meiosis, the matching chromosomes first join up in pairs.

0:41The partners swap small pieces, which mixes up the genes.

0:45The pairs line up across the middle, and the first division pulls each pair apart.

0:51So each new cell has one chromosome from each pair: two, not four.

0:57Then the second division pulls the copies apart: two divisions, four cells.

1:04So meiosis is not mitosis twice: the chromosomes are copied only once, and the first division splits the pairs.

1:13Mitosis keeps the chromosome number the same, and meiosis halves it: in humans, 46 and 23.

1:21Mitosis makes genetically identical cells, with the same genes. Meiosis makes cells that are all genetically different.

1:31Mitosis is for growth and repair. Meiosis makes sex cells, also called gametes.

1:38Mitosis copies a cell exactly; meiosis halves the chromosomes and mixes the genes.