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Biology LibreTexts

4.S: Mutation and Variation (Summary)

  • Page ID
    4034
    • When a variation in DNA sequence originated recently, and is rare in a population, we call that change a mutation.
    • When variations in DNA sequence co-exist in a population, and neither one can be meaningfully defined as wild-type, we call the variations polymorphisms.
    • Mutations may either occur spontaneously, or may be induced by exposure to mutagens.
    • Mutations may result in either substitutions, deletions, or insertions.
    • Mutation usually causes either a partial or complete loss of function, but sometimes results in a gain of function,including new functions.
    • Spontaneous mutations arise from many sources including natural errors in DNA replication, usually associated with base mispairing, or else insertion deletion especially within repetitive sequences.
    • Induced mutations result from mispairing, DNA damage, or sequence interruptions caused by chemical, biological, or physical mutagens.
    • By randomly inducing mutations, then screening for a specific phenotype, it is possible to identify genes associated with specific biological pathways.
    • Transposable elements are dynamic, abundant components of eukaryotic genomes and important forces in evolution.
    • Transposable elements are dynamic, abundant components of eukaryotic genomes and important forces in evolution.
    • The efficiency of mutant screening is limited by silent mutations, redundancy, and embyronic lethality.
    • Mutation of different genes can produce a similar phenotype.
    • Complementation testing determines whether two mutants are the result of mutation of the same gene (allelic mutations), or if each mutant is caused by mutation of a different gene (non-allelic mutations).

    Key Terms

    mutation

    mutant

    polymorphism

    insertion

    deletion

    substitution

    mutagen

    DNA replication error

    Strand slippage

    biological mutagen

    chemical mutagen

    physical mutagen

    mispairing

    loop

    SSR

    insertional mutagen

    Class I, Class II

    transposon

    retrotransposon

    reverse transcriptase

    transposase

    non-autonomous

    autonomous

    SINE, LINE, Alu

    P-element

    T-DNA

    copy-and-paste

    cut-and-paste

    alkylation agent

    EMS

    intercalating agent

    benzopyrene

    carcinogenic

    ethidium bromide

    thymine dimer

    mutant screen

     

    loss-of-function

    gain-of-function

    amorph

    null

    hypomorph

    hypermorph

    neopmorph

    dominant negative

    somatic cells

    germline cells

     

    silent mutation

    inter-genic region

    redundancy

    essential gene

    recessive lethal allele

    complementation testing

    allelic / non-allelic

    cM0, M1, M2

    redundancy

    lethality

    allelic

    non-allelic

    complementation group

    CFTR

    Cystic Fibrosis (CF)

    DF508(PHE508DEL)

    Kalydeco

     

     

     

     

     

     

     

    Contributors