What happens to the chromosome number during meiosis?

During meiosis, the chromosome number decreases from diploid to haploid. This essential process occurs in two main stages: meiosis I and meiosis II.

In meiosis I, homologous chromosomes, each consisting of two sister chromatids, are separated into different cells. This reductional division is responsible for halving the chromosome number. For example, in a diploid organism with two sets of chromosomes (2n), meiosis will result in cells with only one set of chromosomes (n), thus transitioning from a diploid to a haploid state.

Meiosis II resembles mitosis, where the sister chromatids are separated, but since the starting point was already haploid after meiosis I, it does not change the haploid status of the cells. The emphasis during meiosis is on reducing the genetic material to ensure that gametes (sperm and eggs) have the appropriate number of chromosomes, which, upon fertilization, will restore the diploid number. This reduction in chromosome number is critical for maintaining the chromosome count across generations in sexually reproducing organisms.