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What is meiosis?
What is meiosis?
A type of cell division that results in four daughter cells, each with half the number of chromosomes of the parent cell.
What are the two main purposes of meiosis?
What are the two main purposes of meiosis?
To generate haploid cells from a diploid cell and to create genetic diversity.
How is a diploid zygote formed?
How is a diploid zygote formed?
Opposite gametes fuse together in fertilisation to produce a diploid zygote.
What are the two types of cell division in meiosis?
What are the two types of cell division in meiosis?
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What happens during prophase I?
What happens during prophase I?
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What happens during prometaphase I?
What happens during prometaphase I?
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What happens during metaphase I?
What happens during metaphase I?
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What happens during anaphase I?
What happens during anaphase I?
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What happens during telophase and cytokinesis I?
What happens during telophase and cytokinesis I?
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What happens during prophase II?
What happens during prophase II?
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What happens during pro/metaphase II?
What happens during pro/metaphase II?
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What happens during anaphase II?
What happens during anaphase II?
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What happens during telophase and cytokinesis II?
What happens during telophase and cytokinesis II?
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What process makes meiosis distinct from mitosis?
What process makes meiosis distinct from mitosis?
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What process happens at chiasmata?
What process happens at chiasmata?
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What are the 5 phases of meiotic prophase I?
What are the 5 phases of meiotic prophase I?
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What happens during Leptotene?
What happens during Leptotene?
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What happens during Zygotene?
What happens during Zygotene?
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What happens during Pachytene?
What happens during Pachytene?
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What happens during Diplotene?
What happens during Diplotene?
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What happens during Diakinesis?
What happens during Diakinesis?
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How does meiosis generate genetic diversity?
How does meiosis generate genetic diversity?
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What are the similarities and differences between meiosis and mitosis?
What are the similarities and differences between meiosis and mitosis?
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What can errors in chromosome segregation during meiosis lead to?
What can errors in chromosome segregation during meiosis lead to?
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Study Notes
Meiosis Overview
- Meiosis is a specialized cell division resulting in four daughter cells, each with half the chromosomes of the parent cell, crucial for gamete and spore production.
Purposes of Meiosis
- Generates haploid gametes from diploid germline cells.
- Creates genetic diversity in the resulting cells.
Formation of Diploid Zygote
- Occurs when two opposite gametes fuse during fertilization, leading to a diploid zygote that undergoes mitosis to form a diploid organism.
Stages of Meiosis
- Two main stages: Meiosis I and Meiosis II.
Key Events in Meiosis I
- Prophase I: Chromosomes condense, pair up, and spindle apparatus forms.
- Prometaphase I: Breakdown of nuclear envelope; spindle fibers attach to chromosomes.
- Metaphase I: Homologous chromosomes align at the cell equator.
- Anaphase I: Separation of homologous chromosomes occurs.
- Telophase I and Cytokinesis: Creation of two diploid cells.
Key Events in Meiosis II
- Prophase II: Spindle apparatus re-forms.
- Prometaphase II: Nuclear envelope breaks down; chromosomes align.
- Anaphase II: Sister chromatids are separated.
- Telophase II and Cytokinesis: Four non-identical haploid cells are produced.
Distinctions from Mitosis
- In mitosis, chromosomes operate independently, whereas homologous chromosomes pair in meiosis.
- Chiasmata form in meiosis, facilitating homologous chromosome pairing.
- Sister chromatids are held together by cohesin in mitosis, while bivalents are held by chiasmata in meiosis.
Crossing Over
- Chiasmata are the sites where crossing over occurs, allowing genetic recombination between homologous chromosomes.
Phases of Meiotic Prophase I
- Five phases: Leptotene, Zygotene, Pachytene, Diplotene, Diakinesis:
- Leptotene: Homologs begin to pair.
- Zygotene: Synaptonemal complex forms to stabilize homologs.
- Pachytene: Complete synapsis occurs along chromosome lengths.
- Diplotene: Synaptonemal complex disassembles.
- Diakinesis: Chromosomes further condense.
Genetic Diversity Mechanisms
- Independent assortment of maternal and paternal chromosomes leads to 2^n different gamete combinations.
- Crossing over exchanges genetic material, enhancing diversity.
Meiosis vs. Mitosis
- Meiosis II resembles mitosis but includes chromosome pairing.
- DNA synthesis precedes both processes, and both complete cell division.
- Meiosis produces four genetically diverse haploid cells; mitosis yields two identical diploid cells.
- Meiosis involves two rounds of division without recombination in mitosis; meiosis maintains cohesion in meiosis I but not in mitosis.
Errors in Meiosis
- Improper chromosome segregation can result in gametes with abnormal chromosome numbers.
- Errors in recombination may lead to structural chromosome abnormalities.
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Test your knowledge on meiosis with these flashcards. Covering key concepts, such as the definition of meiosis and its main purposes, this quiz will help reinforce your understanding of this crucial cell division process.