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Meiosis and Genetic Variation in General Biology

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  • What is meiosis?
    Meiosis is a type of cell division that reduces the chromosome number by half, producing four haploid daughter cells from one diploid parent cell.
  • How many rounds of cell division occur in meiosis?
    Meiosis consists of two rounds of cell division: Meiosis I and Meiosis II.
  • What happens during Meiosis I?
    Homologous chromosomes separate during anaphase I, reducing the ploidy from diploid (2n) to haploid (n), but chromosomes remain duplicated.
  • What happens during Meiosis II?
    Sister chromatids separate during anaphase II, but the ploidy remains haploid (n) because chromosomes are no longer duplicated.
  • What is the difference between meiosis and mitosis in terms of daughter cells?
    Meiosis produces four haploid genetically distinct daughter cells, while mitosis produces two diploid identical daughter cells.
  • What is crossing over and when does it occur?
    Crossing over is the exchange of genetic material between homologous chromosomes during prophase I, increasing genetic variation.
  • What is independent assortment?
    Independent assortment is the random distribution of maternal and paternal chromosomes into gametes during meiosis, contributing to genetic diversity.
  • How many possible chromosome combinations can humans produce through independent assortment?
    Humans have 23 homologous pairs, leading to \(2^{23}\) (about 8.4 million) possible combinations.
  • How does fertilization affect chromosome number?
    Fertilization restores the diploid chromosome number (2n) by fusing two haploid gametes (n).
  • What is nondisjunction?
    Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during meiosis, causing aneuploidy.
  • What are the consequences of nondisjunction during meiosis I?
    Nondisjunction in meiosis I results in gametes with an extra chromosome or missing one, affecting all resulting cells.
  • What are the consequences of nondisjunction during meiosis II?
    Nondisjunction in meiosis II affects only half of the gametes, producing some with abnormal chromosome numbers.
  • What is a bivalent in meiosis?
    A bivalent is a paired set of homologous chromosomes physically connected during prophase I.
  • What is a chiasma?
    A chiasma is the site where crossing over occurs between non-sister chromatids of homologous chromosomes.
  • How do mitosis and meiosis differ in the number of cell divisions?
    Mitosis involves one cell division; meiosis involves two cell divisions.
  • What is the role of meiosis in the organism life cycle?
    Meiosis produces haploid gametes for sexual reproduction, halving chromosome number to maintain stability across generations.
  • What is the role of mitosis in the organism life cycle?
    Mitosis supports growth, tissue repair, and asexual reproduction by producing genetically identical diploid cells.
  • What is synapsis?
    Synapsis is the pairing of homologous chromosomes during prophase I of meiosis.
  • What is the difference in DNA content between daughter cells after mitosis and meiosis?
    After mitosis, daughter cells have the same DNA content as the parent; after meiosis, daughter cells have half the DNA content.
  • What is the significance of sister chromatid separation in meiosis II?
    Separation of sister chromatids in meiosis II ensures each gamete receives one copy of each chromosome.