Continuity and change - Cell and nuclear division

The cell cycle is an ordered sequence of events: Interphase (comprising $G_1$, $S$, and $G_2$ phases) followed by the M-phase (mitosis and cytokinesis).

DNA replication occurs during the $S$ phase of interphase to ensure that each daughter cell receives a complete set of genetic information.

Mitosis consists of four main stages: Prophase, Metaphase, Anaphase, and Telophase (PMAT), resulting in two genetically identical diploid ($2n$) daughter nuclei.

Cytokinesis is the physical division of the cytoplasm. In animal cells, it involves a cleavage furrow; in plant cells, it involves the formation of a cell plate.

Cyclins are a group of proteins that regulate the cell cycle by binding to cyclin-dependent kinases (CDKs), ensuring tasks are performed at the correct time.

Meiosis involves two consecutive nuclear divisions (Meiosis I and Meiosis II) to produce four non-identical haploid ($n$) daughter cells.

Genetic variation in meiosis is promoted by crossing over during Prophase I and independent assortment of bivalents during Metaphase I.

Non-disjunction is the failure of homologous chromosomes or sister chromatids to separate properly, leading to aneuploidy (e.g., Down Syndrome, which is Trisomy $21$).