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Questions and Answers
What is the purpose of the synaptonemal complex during meiosis?
What is the purpose of the synaptonemal complex during meiosis?
What occurs during meiosis I: Anaphase I?
What occurs during meiosis I: Anaphase I?
What is the result of crossing-over during meiosis?
What is the result of crossing-over during meiosis?
What occurs during meiosis II: Prophase II?
What occurs during meiosis II: Prophase II?
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What is the purpose of the chiasmata during meiosis?
What is the purpose of the chiasmata during meiosis?
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What is the result of meiosis I?
What is the result of meiosis I?
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What occurs during meiosis II: Anaphase II?
What occurs during meiosis II: Anaphase II?
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What is the similarity between meiosis II and mitosis?
What is the similarity between meiosis II and mitosis?
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What is the main function of the centrosome during interphase?
What is the main function of the centrosome during interphase?
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What type of microtubules are involved in the attachment to kinetochores?
What type of microtubules are involved in the attachment to kinetochores?
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During which phase of mitosis do the chromosomes become apparent?
During which phase of mitosis do the chromosomes become apparent?
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What is the function of the kinetochores during mitosis?
What is the function of the kinetochores during mitosis?
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What is the main function of the mitotic spindle during mitosis?
What is the main function of the mitotic spindle during mitosis?
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During which phase of mitosis does the nuclear membrane break down?
During which phase of mitosis does the nuclear membrane break down?
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What is the result of the cytokinesis process?
What is the result of the cytokinesis process?
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Which type of cells do not have centrosomes?
Which type of cells do not have centrosomes?
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What is the primary mechanism responsible for the rapid degradation of cyclin concentration during mitosis?
What is the primary mechanism responsible for the rapid degradation of cyclin concentration during mitosis?
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What is the role of the anaphase promoting complex (APC) in mitosis regulation?
What is the role of the anaphase promoting complex (APC) in mitosis regulation?
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Which of the following cyclin-Cdk complexes is responsible for triggering the entry into the S phase?
Which of the following cyclin-Cdk complexes is responsible for triggering the entry into the S phase?
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What is the consequence of cyclin degradation in the cell cycle?
What is the consequence of cyclin degradation in the cell cycle?
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What is the role of M-Cdk in its own deactivation?
What is the role of M-Cdk in its own deactivation?
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What is the primary function of the proteasome in the context of cyclin regulation?
What is the primary function of the proteasome in the context of cyclin regulation?
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What is the consequence of APC complex activation during mitosis?
What is the consequence of APC complex activation during mitosis?
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What is the role of different cyclin-Cdk complexes in the cell cycle?
What is the role of different cyclin-Cdk complexes in the cell cycle?
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Study Notes
Meiosis I: Synapsis
- The synaptonemal complex, also known as the "zipper", aligns homologous chromosomes with remarkable precision, bringing together corresponding genetic regions of the chromosome pair.
- Sister chromatids do not undergo recombination.
- The sites of crossing-over are called chiasmata (singular, chiasma), resulting in the recombination of genetic material.
- No genetic information is lost or gained, and all chromatids retain their original size.
Meiosis I: Metaphase I, Anaphase I, and Telophase I
- Homologous chromosomes move to opposite poles.
- Nuclear envelope reforms.
- Resultant cells have half the number of chromosomes, each consisting of two sister chromatids.
Meiosis II
- Resembles Mitosis, with prophase, metaphase, anaphase, and telophase stages.
- Chromosomes condense, centrioles move towards the poles, and the nuclear envelope breaks down at the end of prophase II.
- Chromosomes align at the metaphase plate.
- Sister chromatids attach to the spindle fibers from opposite poles.
- Centromeres divide, and sister chromatids move to opposite poles.
Cell Cycle Regulation
- The sudden drop in cyclin concentration during mitosis is due to its rapid degradation by the ubiquitin-dependent proteolytic system.
- The anaphase promoting complex (APC) adds ubiquitin to cyclin and other proteins involved in mitotic regulation.
- M-Cdk contributes to its own deactivation.
- Different cyclin-Cdk complexes trigger different steps in the cell cycle.
- E.g., M-cyclin-Cdk complex acts in the G2 phase and triggers the entry into the M phase, while S-phase cyclins are responsible for the entry into the S phase.
Mitosis
- Chromosomes are lined up at the metaphase plate, an imaginary structure at the midway point between the spindle's two poles.
- Centrosomes duplicate during Interphase, and each centrosome migrates during prophase to either side of the nucleus to form spindle poles.
- Plant cells do not have centrosomes.
- Kinetochores are protein complexes associated with centromeres, and microtubules attach to kinetochores found at the centromere.
- Mitosis is conventionally divided into five phases: prophase, prometaphase, metaphase, anaphase, and telophase.
- Cytokinesis is the division of cytoplasm, resulting in the formation of new cell membranes and the separation of cells.
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Description
Learn about the process of synapsis in meiosis I, including the role of the synaptonemal complex and the formation of chiasmata. Understand how this process leads to genetic recombination.
