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Cell Cycle, Mitosis & Meiosis
Cells divide on a tightly regulated schedule. You will follow the phases and checkpoints, connect cyclins, p53, and Rb to cancer, compare mitosis with meiosis, and predict the outcome of nondisjunction.
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What this chapter covers
- The Cell Cycle & Its Controls. The MCAT tests which phase does what, how cyclin-CDK complexes drive the cycle, and what each checkpoint guards.
- Mitosis & Cytokinesis. Mitosis makes two genetically identical diploid cells. Know the phases and what happens to chromosome and chromatid counts.
- Cancer, p53 & Rb. Cancer is a disease of broken cell-cycle controls. Know oncogenes versus tumor suppressors and what p53 and Rb do.
- Meiosis. Meiosis halves chromosome number and shuffles alleles. Distinguish meiosis I from II and know where variation arises.
- Nondisjunction & Aneuploidy. When chromosomes fail to separate, gametes carry the wrong number. Predict which gametes result and which syndromes follow.
Key points to know
- Interphase = G1 + S + G2; DNA is replicated in S
- CDK levels are constant; cyclin levels oscillate; the complex is the active kinase
- Mitosis: prophase, prometaphase, metaphase, anaphase, telophase; cytokinesis follows
- Sister chromatids separate at anaphase
- Oncogenes: gain of function, dominant; tumor suppressors: loss of function, two hits
- Rb binds E2F; CDK phosphorylation of Rb releases E2F and permits S phase
- Meiosis I is reductional: homologs separate; meiosis II separates sister chromatids
- Synapsis and crossing over occur in prophase I
Try a practice question
In which phase of the cell cycle is DNA replicated?
- S
- G1
- G2
- M
Show the answer
A. Replication takes place in S phase, raising DNA content from 2C to 4C. G2 is a preparation and checking phase after replication.
Common questions
What does this chapter cover?
Cell Cycle, Mitosis & Meiosis covers The Cell Cycle & Its Controls, Mitosis & Cytokinesis, Cancer, p53 & Rb, Meiosis, Nondisjunction & Aneuploidy.
What should I know first?
Interphase = G1 + S + G2; DNA is replicated in S CDK levels are constant; cyclin levels oscillate; the complex is the active kinase Mitosis: prophase, prometaphase, metaphase, anaphase, telophase; cytokinesis follows
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