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Biology LibreTexts

2.S: Chromosomes, Mitosis, and Meiosis (Summary)

  • Page ID
    4014
  • [ "article:topic", "OOG", "OGG", "authorname:tnickle" ]

    • Chromosomes are complex and dynamic structures consisting of DNA and proteins (chromatin).
    • The degree of chromatin compaction involves proteins and varies between heterochromatic and euchromatic regions and among stages of the cell cycle.
    • Chromosomes can be distinguished cytologicaly based on their length, centromere position, and banding patterns when stained dyes or labeled with sequence-specific probes.
    • Homologous chromosomes contain the same series of genes along their length, but not necessarily the same alleles.Sister chromatids initially contain the same alleles.
    • Chromosomes are replicated by DNA polymerases and begin at an origin. Replication is bi-directional. Eukaryotes have multiple origins along each chromosome and have telomerase to replicate the ends.
    • Mitosis reduces the c-number, but not the n-number.Meiosis reduces both c and n.
    • Homologous chromosomes pair (sysnapse) with each other during meiosis, but not mitosis.
    • Several types of structural defects in chromosomes occur naturally, and can affect cellular function and even evolution.
    • Aneuploidy results from the addition or subtraction of one or more chromosomes from a group of homologs, and is usually deleterious to the cell.
    • Polyploidy is the presence of more than two complete sets of chromosomes in a genome.Even-numbered multiple sets of chromosomes can be stably inherited in some species, especially plants.
    • Endopolyploidy is tissue-specific type of polyploidy observed in some species, including diploids.
    • Both aneuploidy and structural defects such as duplications can affect gene balance.
    • Organelles also contain chromosomes, but these are much more like prokaryotic chromosomes than the nuclear chromosomes of eukaryotes.

    Key Terms

    chromosome

    core histones

    nucleosome

    30nm fiber

    histone H1

    scaffold proteins

    heterochromatin

    euchromatin

    satellite DNA

    chromatid

    centromere

    metacentric

    acrocentric

    telocentric

    holocentric

    telomere

    homologous

    non-homologous

    chromatid

    sister chromatid

    non-sister chromatid

    interphase

    mitosis

    prophase

    metaphase

    anaphase

    telophase

    DNA polymerase

    origin of replication

    telomerase

    riboprotein

    Hayflick limit

    HeLa cells

    cytokinesis

    meiosis

    gametes

    prophase (I, II)

    metaphase (I, II)

    anaphase (I, II)

    telophase (I, II)

    cytokinesis

    meiocyte

    bivalent

    syanapse, pair up

    synaptonemal complex

    reductional division

    equational division

    leptotene

    zygotene

    pachytene

    diplotene

    diakinesis

    crossing over

    chiasma (chiasmata)

    polar bodies

    G1

    G2

    S

    M

    G0

    interphase

    n

    c

    replicated chromosome

    karyotype/karyogram

    autosome

    sex-chromosome

    homogametic

    heterogametic

    aneuploidy

    monsomic

    trisomic

    Down syndrome

    deletion

    duplication

    insertion

    inversion

    translocation

    non-disjunction

    chromosome breakage

    polyploidy

    x

    monoploid

    sterile

    tetravalent

    octoploid

    hexaploid

    triploid

    endoreduplication

    endopolyploidy

    salivary gland chromosome

    polytene

    gene balance

    cellular network

    chloroplast

    mitochondria

    endosymbiont

    endosymbiont theory

    organellar chromosome

    mtDNA

     

     

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