Biology / Unit 4: Cell Growth and Division
4.1 Chromosomes and the Cell Cycle
Notes
The cell cycle is the series of events a cell goes through as it grows and divides.
- Interphase is most of the cycle: G1 (growth), S (DNA is copied), G2 (prepares to divide).
- The mitotic (M) phase includes mitosis (nucleus divides) and cytokinesis (cytoplasm divides).
- DNA is packed into chromosomes. After S phase, each chromosome has two identical sister chromatids joined at a centromere.
- Humans have 46 chromosomes (23 pairs) in body cells.
- Cells divide for growth, repair and asexual reproduction.
Practice
During which phase is DNA copied?
S stands for synthesis, when DNA replicates.
A cell spends most of its life in which stage?
Interphase includes G1, S and G2, the longest part of the cycle.
Sister chromatids are:
They form when DNA is copied in S phase.
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