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General Biology: Sexual Life Cycles and Meiosis

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  • What is heredity?

    Heredity is the transmission of traits from one generation to the next.

  • What are genes and alleles?

    Genes are units of heredity made of DNA segments. Alleles are alternative versions of a gene.

  • What is the difference between haploid and diploid cells?

    Haploid (n) cells have one set of chromosomes (23 in humans), like gametes. Diploid (2n) cells have two sets (46 in humans), like somatic cells.

  • What are homologous chromosomes?

    Homologous chromosomes are pairs of chromosomes carrying genes for the same inherited characters, one from each parent.

  • What is a karyotype?

    A karyotype is an ordered display of chromosome pairs from a cell.

  • Compare sexual and asexual reproduction.

    Sexual reproduction involves two parents and produces genetically unique offspring. Asexual reproduction involves one parent producing genetically identical offspring (clones).

  • What is the role of gametes in the human life cycle?

    Gametes (sperm and egg) are haploid cells produced by meiosis that fuse during fertilization to form a diploid zygote.

  • How does meiosis reduce chromosome number?

    Meiosis reduces chromosome number from diploid to haploid through two consecutive divisions: meiosis I and meiosis II.

  • What happens during Prophase I of meiosis?

    Homologous chromosomes pair up and crossing over occurs at chiasmata, exchanging DNA segments.

  • What is synapsis in meiosis?

    Synapsis is the tight pairing of homologous chromosomes held by the synaptonemal complex during Prophase I.

  • Describe Metaphase I of meiosis.

    Pairs of homologous chromosomes line up at the metaphase plate, with microtubules attached to kinetochores of each homolog.

  • What occurs during Anaphase I?

    Homologous chromosomes separate and move to opposite poles; sister chromatids remain attached.

  • What is the result of Telophase I and Cytokinesis?

    Two haploid daughter cells form, each with duplicated chromosomes consisting of sister chromatids.

  • How is meiosis II similar to mitosis?

    Meiosis II separates sister chromatids into individual chromosomes, similar to mitosis, resulting in haploid cells.

  • What happens during Metaphase II?

    Sister chromatids line up at the metaphase plate with kinetochores attached to microtubules from opposite poles.

  • Describe Anaphase II.

    Sister chromatids separate and move as individual chromosomes toward opposite poles.

  • What is the final outcome of meiosis?

    Four genetically distinct haploid daughter cells, each with unreplicated chromosomes.

  • What mechanisms contribute to genetic variation in meiosis?

    Genetic variation arises from crossing over, independent assortment of chromosomes, and random fertilization.

  • What is crossing over?

    Crossing over produces recombinant chromosomes by exchanging DNA between nonsister chromatids during Prophase I.

  • Explain independent assortment of chromosomes.

    During Metaphase I, homologous pairs orient randomly, sorting maternal and paternal chromosomes independently into daughter cells.