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Mutations (2 of 2)

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The only mutations that matter to large-scale evolution are those that can be passed on to offspring. These occur in reproductive cells like eggs and sperm and are called germ line mutations.

A single germ line mutation can have a range of effects:

  1. No change occurs in phenotype.
    Some mutations don't have any noticeable effect on the phenotype of an organism. This can happen in many situations: perhaps the mutation occurs in a stretch of DNA with no function, or perhaps the mutation occurs in a protein-coding region, but ends up not affecting the amino acid sequence of the protein.

  2. Small change occurs in phenotype.
    Cat with curled-ear mutation
    A single mutation caused this cat’s ears to curl backwards slightly.

  3. Big change occurs in phenotype.
    Some really important phenotypic changes, like DDT resistance in insects are sometimes caused by single mutations1. A single mutation can also have strong negative effects for the organism. Mutations that cause the death of an organism are called lethals—and it doesn't get more negative than that.

There are some sorts of changes that a single mutation, or even a lot of mutations, could not cause. Neither mutations nor wishful thinking will make pigs have wings; only pop culture could have created Teenage Mutant Ninja Turtles—mutations could not have done it.

Explore further
•  Mutations are random
•  The Lederberg experiment

Teach this!
Lesson plans for teaching about mutation

Next Topic:
Causes of Mutations
1 Williamson et al., 1996.
• Cat with curled ears image by Renate Wald, courtesy of American Curl Rescue Project

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