Summary of the cell cycle
- Mitosis is equatorial cell division that results in two genetically identical daughter cells. It is used to produce new cells in a multicellular organism and in asexual reproduction. Meiosis is reductive cell division used to produce gametes for sexual reproduction. It produces four daughter cells with half the DNA content of the parent cell.
- The cell cycle consists of G1, S, G2, and M stages. G1, S, and G2 stages together make up an interphase. The DNA content of a cell doubles during S phase, when replication occurs, but chromosome number does not change because chromatids stay connected. Chromatids separate in M phase, or mitosis.
- Mitosis consists of prophase, metaphase, anaphase, and telophase, followed by cytokinese. Meiosis consists of two divisions: meiosis I and meiosis II. Meiosis I is divided into prophase I, metaphase I, anaphase I, and telophase I. Homologous pairs separate in meiosis I, resulting in haploid daughter cells. Meiosis II is divided into prophase II, metaphase II, anaphase II, and telophase II. Sister chromatids separate in meiosis II.
- The process of meiosis is different between sexes, with all four products of meiosis producing viable sperm, but only one product of meiosis producing a viable egg.
- Nondisjunction of chromosomes and other errors during mitosis and meiosis can lead to aneuploidies and polyploids. Polyploid genomes are common in plants. Aneuploid cells and cells with an odd ploidy cannot undergo meiosis because they arrest in meiosis I when chromosomes cannot form pairs.
