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Meiosis and Genetic Variation - General Biology

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  • What is a karyotype?

    A karyotype is the complete set of chromosomes in a cell, arranged and displayed in pairs.

  • How many pairs of chromosomes do humans have?

    Humans have 23 pairs of chromosomes.

  • What are the 22 non-sex chromosomes called?

    The 22 non-sex chromosomes are called autosomes.

  • What are homologous chromosomes?

    Homologous chromosomes are pairs of chromosomes that have the same genes at the same loci but may have different alleles.

  • What is a cell with paired chromosomes called?

    A cell with paired chromosomes is called diploid.

  • What does the haploid number (n) represent?

    The haploid number (n) represents the number of chromosomes in a gamete, which is half the diploid number.

  • Why are gametes haploid?

    Gametes (sperm and eggs) are haploid because they contain half the number of chromosomes of a diploid cell.

  • What are the human sex chromosomes?

    Human sex chromosomes are X and Y.

  • What are different versions of a gene called?

    Different versions of a gene are called alleles.

  • How do alleles arise?

    Alleles arise from changes in DNA called mutations.

  • How does sexual reproduction increase genetic variability?

    Sexual reproduction increases genetic variability by combining genetic material from two different gametes.

  • What are the two main stages of meiosis?

    Meiosis consists of Meiosis I and Meiosis II.

  • How many haploid daughter cells does meiosis produce from one diploid cell?

    Meiosis produces four haploid daughter cells from one diploid cell.

  • When is DNA replicated in meiosis?

    DNA is replicated before the first meiotic division.

  • What does Meiosis I separate?

    Meiosis I separates homologous chromosomes.

  • What does Meiosis II separate?

    Meiosis II separates sister chromatids.

  • What happens during prophase I of meiosis?

    During prophase I, homologous chromosomes pair and exchange DNA in a process called crossing over.

  • What are the physical points where chromosomes exchange DNA called?

    The physical points where chromosomes exchange DNA are called chiasmata.

  • What does crossing over create?

    Crossing over creates new combinations of alleles called recombinant chromosomes.

  • What is the random lining up of homologous pairs during metaphase I called?

    This random alignment is called independent assortment.

  • What separates during anaphase I?

    During anaphase I, homologous chromosomes separate.

  • Are the two nuclei after telophase I diploid or haploid?

    After telophase I, the two nuclei are haploid.

  • Which process is meiosis II most similar to?

    Meiosis II is most similar to mitosis.

  • What lines up at the equator during metaphase II?

    During metaphase II, sister chromatids line up at the equator.

  • What splits during anaphase II?

    During anaphase II, sister chromatids split.

  • How many haploid daughter cells are produced at the end of meiosis II?

    At the end of meiosis II, four haploid daughter cells are produced.

  • When does random assortment occur?

    Random assortment occurs during metaphase I of meiosis.

  • When does crossing over occur?

    Crossing over occurs during prophase I of meiosis.

  • Why does fertilization add genetic variability?

    Fertilization adds variability because it combines genetic material from two genetically unique gametes.

  • What are errors in meiosis called?

    Errors in meiosis are called nondisjunction or chromosomal abnormalities.

  • What does nondisjunction result in?

    Nondisjunction results in gametes with an abnormal number of chromosomes.

  • Give an example of a disorder caused by nondisjunction of autosomes.

    An example is Down syndrome, caused by trisomy 21.

  • What is the genotype of Turner syndrome?

    Turner syndrome genotype is X0 (one X chromosome, no second sex chromosome).

  • What is the genotype of Klinefelter syndrome?

    Klinefelter syndrome genotype is XXY.

  • What is the genotype of Trisomy X?

    Trisomy X genotype is XXX.

  • What is the genotype of Jacob syndrome?

    Jacob syndrome genotype is XYY.