Gene flow, drift and inbreeding don't make new alleles
- The idea
- Predict
- See it
- Why
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The idea
“An allele that shows up after migration, drift or inbreeding was made by that event.”
An allele can seem to appear from nowhere when migrants arrive or inbred animals show a disorder. It was already there.
The short version
The mistake: An allele that shows up after migration, drift or inbreeding was made by that event.
What's actually true: Only mutation creates new alleles. Gene flow, drift and inbreeding move them, change how common they are, or pair them up.
- Only a change in the DNA, a mutation, makes a new allele. In animals, it's inherited only if it happens in a cell that makes gametes.
- Gene flow carries alleles between populations in migrants or pollen. Drift changes their frequencies by chance, most in small populations. Neither makes new ones.
- Inbreeding, mating between relatives, makes offspring homozygous more often. Hidden recessive alleles show up, but they were there all along.
On the exam: Only mutation makes new alleles. Gene flow moves them, drift changes their frequency, inbreeding pairs them.