Meiosis

Science

Definition

Meiosis is a type of cell division that produces four genetically unique haploid cells (gametes) from one diploid parent cell. It involves two rounds of division (meiosis I and meiosis II) and is essential for sexual reproduction, introducing genetic variation through crossing over and independent assortment.

How It Works

  1. DNA replicates during interphase, producing duplicated chromosomes.
  2. In meiosis I, homologous chromosomes pair up and crossing over occurs during prophase I.
  3. Homologous pairs separate during anaphase I, reducing chromosome number by half.
  4. In meiosis II, sister chromatids separate, similar to mitosis.
  5. Four genetically unique haploid daughter cells are produced.

Examples

  • Human egg and sperm cells each containing 23 chromosomes
  • Crossing over creating new allele combinations on chromosomes
  • Independent assortment producing 2²³ possible gamete combinations in humans
Key Fact

Meiosis produces 4 haploid cells (n) from 1 diploid cell (2n).

Related Terms

Mitosis Cell cycle Mendelian genetics Reproduction in plants

Study This Concept

Practice meiosis with free review games in these units:

AP Biology Unit 5: Heredity