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Anatomy Unit 4

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Terms in this set (31)

  • Why do cells divide?

    For growth, repair, replacement of old or dead cells, production of new cells, production of gametes, and specialization of cells.

  • What are the two main types of cell division?

    Mitosis (growth, repair, replacement) and Meiosis (production of gametes).

  • What is the chromosome number in most human body cells?

    46 chromosomes arranged in 23 pairs; these cells are diploid (2n).

  • Define haploid cells.

    Cells with one copy of each chromosome (n), such as human gametes with 23 chromosomes.

  • What are homologous chromosomes?

    Chromosome pairs of similar size and shape carrying the same genes but possibly different alleles, one from each parent.

  • Define gene, allele, and locus.

    Gene: DNA region coding for a product.
    Allele: Different versions of a gene.
    Locus: Specific gene location on a chromosome.

  • What are autosomes and sex chromosomes?

    Pairs 1–22 are autosomes (body traits), pair 23 are sex chromosomes (XX or XY).

  • What is a gamete?

    A reproductive cell (sperm or egg) that is haploid with 23 chromosomes.

  • What happens during fertilization?

    Sperm (n=23) and egg (n=23) combine to form a diploid zygote (2n=46).

  • What are the two major parts of the cell cycle?

    Interphase (G1, S, G2) and Mitotic phase (mitosis + cytokinesis).

  • What occurs during the S phase of interphase?

    DNA replication; each chromosome duplicates to form two identical sister chromatids.

  • What are sister chromatids?

    Two identical copies of a chromosome connected at the centromere after DNA replication.

  • Difference between chromosome and chromatid?

    Before replication: 1 chromosome = 1 chromatid.
    After replication: 1 chromosome = 2 sister chromatids.
    Separated chromatids become individual chromosomes.

  • What is the G0 phase?

    A resting, non-dividing state where cells remain alive but do not prepare to divide (e.g., neurons, cardiac muscle cells).

  • What is mitosis and its purpose?

    Nuclear division producing 2 genetically identical diploid cells for growth, repair, and replacement.

  • List the four stages of mitosis.

    Prophase, Metaphase, Anaphase, Telophase.

  • What happens during prophase?

    Chromatin condenses into chromosomes, nuclear envelope breaks down, spindle forms, nucleolus disappears.

  • What is the role of spindle fibers and kinetochores?

    Spindle microtubules move chromosomes by attaching to kinetochores at the centromere.

  • What occurs during metaphase?

    Chromosomes line up at the metaphase plate (middle of the cell).

  • What happens in anaphase?

    Sister chromatids separate and move to opposite poles of the cell.

  • Describe telophase.

    Chromosomes reach poles, uncoil, nuclear envelopes reform, nucleoli reappear, spindle fibers disappear.

  • What is cytokinesis?

    Division of the cytoplasm, physically splitting one cell into two genetically identical diploid cells.

  • What is meiosis and its purpose?

    Special cell division producing 4 genetically different haploid gametes to maintain chromosome number across generations.

  • Why is meiosis necessary?

    To reduce chromosome number by half so fertilization restores diploid number, preventing chromosome doubling each generation.

  • How many divisions occur in meiosis?

    Two divisions: Meiosis I and Meiosis II, with DNA replication only before Meiosis I.

  • What separates during Meiosis I?

    Homologous chromosomes separate; this is called reduction division (diploid to haploid).

  • What is a tetrad?

    A paired set of homologous chromosomes, each with two sister chromatids, totaling four chromatids.

  • What is crossing over?

    Exchange of DNA between homologous chromosomes during Prophase I, increasing genetic variation.

  • Difference between metaphase I and metaphase II?

    Metaphase I: homologous pairs line up.
    Metaphase II: individual chromosomes line up.

  • What separates during anaphase I and anaphase II?

    Anaphase I: homologous chromosomes separate.
    Anaphase II: sister chromatids separate.

  • Final result of meiosis?

    One diploid cell produces four genetically different haploid cells (gametes) with 23 chromosomes each.