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This phase is everything except mitosis
interphase
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Chromosomes condense
Prophase
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Nuclear envelope goes away in this stage
pro-metaphase
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Chromosomes line up on metapase plate
metaphase
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Centromeres split and chromosomes pulled to opposite sides
anaphase
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Chromosomes de-condense, nuclear membrane returns, and cells divide
telophase
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This is where spindles attach chromosomes
centromeres
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5 Bits of Prophase
Lepotene: unpaired but replicated chromosomes can be seen
Zygotene: maternal and paternal homologs pair up and synapse so genes are along eachother = bivalents
Pachytene: chromosomes thicken, crossing over occurs
Diplotene: homologs try to separate but are held together by chiasmata here
Diakenisis: homologous pairs contract
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This holds homologs together in metaphase 1
chiasmata
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Crossing over happens at these sites
chiasmata
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Exchange of genetic information between non-sister chromatids
Crossing over
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Sister chromatids are pulled apart
anaphase 2
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Homologous chromosomes line up
metaphase 1
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Chromosomes with the same length, centromere position, and genes
- Homologous chromosomes
- One from dad, one from mom
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What are two sources of genetic variation?
1. independent assortment
2. Cossing over
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This complex polices the G1 --> S phase
- Cdk2-CyclinA complex
- If there is damaged DNA, S-phase will not begin
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This enzyme is important in apoptosis
Caspase
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- Cyclins are scaffolding proteins
- they bring target proteins close to CDK for interaction
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In late G1 phase, Cyclin A - CDK2 complex activates a transcription factor called E2F so that mitosis can occur
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