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What is meiosis?

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Quick answer

Meiosis is a special type of cell division that makes sex cells — eggs and sperm — each with half the normal number of chromosomes. It also shuffles genes, which is why offspring differ from their parents and from each other.

Key things to understand

  1. It halves the chromosome count, so fertilization can restore the full set.
  2. One cell divides twice to produce four genetically unique cells.
  3. Genes are reshuffled ('crossing over'), creating variation.
  4. It is essential for sexual reproduction and inheritance.
  5. Errors can cause conditions linked to extra or missing chromosomes.

People also ask

How is meiosis different from mitosis?
Mitosis copies a cell into two identical cells; meiosis makes four genetically varied sex cells with half the chromosomes.
Why does meiosis create variation?
It mixes the parents' genes through crossing over and random sorting, so each egg or sperm carries a unique combination.
Why must sex cells have half the chromosomes?
So that when egg and sperm combine, the offspring ends up with the correct full number, not double.