Mutation


Mutation is any inheritable change in genetic material (DNA)
Mutations may be spontaneous or induced

  • spontaneous are random events
    . . - gene-specific mutation rate
    . . . - equals driving force in micro-evolution
    . . - may result from errors in replication
    . . . - one possible explanation for aging
  • induced are associated with identified causal agents
    . . - chemical mutagenic agents
    . . . - usually attributed to man-made environmental pollutants
    . . . - there may be naturally occurring mutagenic chemicals
    . . . . causing locally increased mutation rates
    . . - radiation as a mutagenic agent
    . . . - sometimes attributed to radiation sources concentrated by man
    . . . - there is naturally occurring variation in background radiation
    . . . . causing locally increased mutation rates


    Mutations may be somatic or germ-line

  • somatic refers to non-reproductive (body) cells
    . . - mutation affects only daughter cells of the mutated cell
    . . . - produce mosaic of mutant & normal tissue:
    . . . . strawberry birth marks, freckles
    . . . . most of the common cancers (skin)
    . . - can pass to progeny only in asexual reproduction
  • germ-line refers to reproductive cell
    . . - passed via inheritance to offspring
    . . . - expressed in F-1 progeny if dominant (rare)
    . . . - may be expressed in F-1 progeny if incomplete dominant (common)
    . . . - may persist several generations in carriers if recessive (normal)
    . . - not expressed in individual where mutation occurred


    Mutation describes change in DNA as follows:

  • base substitution
    . . - transition
    . . . - pyrimidine (T, C) to pyrimidiine
    . . . - purine (A, G) to purine
    . . - transversion
    . . . - pyrimidine to purine
    . . . - purine to pyrimidine
  • Insertion
  • Deletion


    mutation effect on polypeptide

  • silent
  • missense
  • nonsense
  • frameshift



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    © 2004 Prof. LaFrance, Ancilla College