Podcast
Questions and Answers
Which of the following events contributes most significantly to genetic variation during meiosis?
Which of the following events contributes most significantly to genetic variation during meiosis?
- Crossing over between homologous chromosomes during prophase I. (correct)
- The replication of DNA during interphase before meiosis I.
- The alignment of chromosomes at the metaphase plate during metaphase II.
- The separation of sister chromatids during anaphase II.
During which stage of meiosis does independent assortment of chromosomes occur, leading to genetic variation?
During which stage of meiosis does independent assortment of chromosomes occur, leading to genetic variation?
- Prophase I
- Telophase II
- Metaphase I (correct)
- Anaphase II
How does anaphase I of meiosis differ from anaphase of mitosis?
How does anaphase I of meiosis differ from anaphase of mitosis?
- In meiosis I, the chromosome number is halved, while in mitosis, it doubles.
- In meiosis I, sister chromatids separate, while in mitosis, homologous chromosomes separate.
- In meiosis I, homologous chromosomes separate, while in mitosis, sister chromatids separate. (correct)
- In meiosis I, the chromosome number doubles, while in mitosis, it remains the same.
Which of the following is the correct sequence of events during prophase I of meiosis?
Which of the following is the correct sequence of events during prophase I of meiosis?
What is the direct outcome of meiosis I?
What is the direct outcome of meiosis I?
What is the significance of chiasmata formation during meiosis?
What is the significance of chiasmata formation during meiosis?
Which of the following events takes place during anaphase II?
Which of the following events takes place during anaphase II?
If a cell with 20 chromosomes undergoes meiosis, how many chromosomes will each daughter cell have at the end of meiosis II?
If a cell with 20 chromosomes undergoes meiosis, how many chromosomes will each daughter cell have at the end of meiosis II?
Which of the following is a key difference between meiosis I and meiosis II?
Which of the following is a key difference between meiosis I and meiosis II?
The synaptonemal complex forms during which stage of meiosis I?
The synaptonemal complex forms during which stage of meiosis I?
Flashcards
Meiosis
Meiosis
A specialized cell division halving chromosome number to create four unique haploid cells, essential for sexual reproduction.
Independent assortment
Independent assortment
Random alignment of homologous chromosome pairs during metaphase I, creating diverse maternal/paternal chromosome combinations in daughter cells.
Crossing over
Crossing over
Exchange of genetic material between homologous chromosomes during prophase I, creating new allele combinations.
Random fertilization
Random fertilization
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Zygotene
Zygotene
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Pachytene
Pachytene
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Metaphase I
Metaphase I
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Anaphase I
Anaphase I
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Anaphase II
Anaphase II
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Telophase II and Cytokinesis
Telophase II and Cytokinesis
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Study Notes
- Meiosis is a specialized type of cell division that reduces the chromosome number by half, resulting in four haploid cells, each genetically distinct from the parent cell
- Essential for sexual reproduction, maintaining a stable chromosome number across generations
- Meiosis consists of two successive nuclear and cellular divisions: Meiosis I and Meiosis II
Genetic Variation
- Meiosis introduces genetic variation through mechanisms like independent assortment, crossing over, and random fertilization
- Independent assortment: During metaphase I, homologous chromosome pairs align randomly, leading to different combinations of maternal and paternal chromosomes in daughter cells
- Crossing over: Occurs in prophase I, where homologous chromosomes exchange genetic material at the chiasmata, creating recombinant chromosomes
- Random fertilization: Any sperm can fuse with any egg, further increasing genetic diversity
- These mechanisms result in offspring with unique combinations of genes, contributing to diversity within populations
Stages of Meiosis I
Prophase I
- The most complex phase, accounting for about 90% of the time required for meiosis
- Subdivided into stages:
- Leptotene: Chromosomes begin to condense and become visible
- Zygotene: Homologous chromosomes pair up (synapsis), forming a synaptonemal complex
- Pachytene: Crossing over occurs; homologous chromosomes exchange genetic material at chiasmata
- Diplotene: Synaptonemal complex disassembles; homologous chromosomes remain connected at chiasmata
- Diakinesis: Chromosomes fully condense, and the nuclear envelope breaks down
Metaphase I
- Homologous chromosome pairs align at the metaphase plate
- Microtubules from opposite poles attach to the kinetochores of each homologous chromosome
Anaphase I
- Homologous chromosomes separate and move toward opposite poles; sister chromatids remain attached
- Differs from mitosis, where sister chromatids separate
Telophase I and Cytokinesis
- Chromosomes arrive at opposite poles
- Nuclear envelope may reform
- Cytokinesis occurs, resulting in two haploid daughter cells, each with duplicated chromosomes
Stages of Meiosis II
Prophase II
- Chromosomes condense
- Nuclear envelope breaks down (if reformed in Telophase I)
Metaphase II
- Sister chromatids align at the metaphase plate
- Microtubules from opposite poles attach to the kinetochores of each sister chromatid
Anaphase II
- Sister chromatids separate and move toward opposite poles
Telophase II and Cytokinesis
- Chromosomes arrive at opposite poles
- Nuclear envelope reforms
- Cytokinesis occurs, resulting in four haploid daughter cells, each with unduplicated chromosomes
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