MUTATIONS: The Raw Material of Evolution

 

A MUTATION is defined as

• • the process by which a gene changes from one allele to another

  • the end result of that allelic change.

Major changes can take place with only a small rearrangement of base pairs on the DNA strand, either due to errors in DNA replication or from outside damage to the DNA.

The difference between adaptation and evolution!

 

• Adaptation is short-term change (via gene expression) in response to environmental factors; it does not (usually) involve permanent genetic change. (Caution: recall epigenesis!)

• Organic Evolution is a shift in allele frequencies in a population (microevolution) which can ultimately lead to speciation (macroevolution) under certain circumstances.

• Individuals ADAPT. (They do not evolve.)

• Populations EVOLVE.

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Only evolution involves overall change in allele frequencies and genetic composition of the main unit of evolution: the population.

 

Key ideas:

• • Mutations can occur "spontaneously" due to errors in DNA replication or other "spontaneous" DNA damage.

  • Mutations can also be induced by outside factors.

  • A mutagen is an agent which increases the frequency of mutagenesis (the generation of mutations), usually by changing the DNA. (note: a carcinogen is a mutagen which causes a carcinoma--a cancer of the epithelial tissues)

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Also note that there's a big difference in the consequences of

• • SOMATIC (body cell) mutations
    and

  • GERMLINE (reproductive cell) mutations.

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Germline Mutations:

• • Mutations affecting the germ (spermatogonial or oogonial) cells are the only mutations with evolutionary consequences.

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Somatic mutations:

• • Mutations that occur in the somatic cells may disrupt the function of that particular cell, causing it to die, or causing it to become cancerous (highly proliferative and nasty!).

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Contributed by Phantom423