The cell cycle, mitosis and meiosis
How a cell divides: the phases of the cycle and its checkpoints, the stages of mitosis, meiosis that makes gametes and shuffles genes, and what happens when division goes wrong (cancer, trisomies).
- 37 cards
- 4 topics
- Free
The outline, topic by topic
Each topic is weighted the way the exam weighs it.
- Concepts
- The steps
- Scenarios
- Understand
A few cards from the deck
Cell cycle: what is it?
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The sequence of G1 (growth), S (DNA replication), G2 (preparation) and M (division).
A cell that no longer divides leaves the cycle into G0, like neurons.
Mitosis: which step comes after "Prophase: the chromosomes condense"?
- Prometaphase: the nuclear envelope breaks down
- Metaphase: the chromosomes line up at the equator
- Anaphase: the sister chromatids separate
- Telophase: two nuclei re-form
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Prometaphase: the nuclear envelope breaks down
The spindle lines up and then separates the chromatids, and the cell splits into two identical cells.
S phase: what is it?
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The phase of the cycle in which DNA is replicated: each chromosome gets two chromatids.
The cell's amount of DNA doubles.
Why does chemotherapy cause hair loss and low blood counts?
- It destroys bone
- It hits every fast-dividing cell, not only the cancerous ones
- It blocks the heart
- It infects the hair
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It hits every fast-dividing cell, not only the cancerous ones
Hair follicles, marrow and mucosa renew very fast.
Checkpoint: what is it?
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A step where the cell checks that its DNA is intact and properly copied before going on.
The p53 protein halts the cycle, or triggers cell death, if DNA is damaged.
Why does meiosis have two divisions?
- The first separates homologous chromosomes, the second sister chromatids
- To make twice as much DNA
- It is a repeated mitosis
- The second is optional
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The first separates homologous chromosomes, the second sister chromatids
One replication for two divisions: the chromosome number is halved.