Meeting by chance doesn't make mating random
- The idea
- Predict
- See it
- Why
- Check
The idea
“If individuals just mate with whoever they happen to meet, mating is random.”
Nobody is choosing a partner, so it seems random. Who you meet depends on where you live, though, and neighbors are often relatives.
The short version
The mistake: If individuals just mate with whoever they happen to meet, mating is random.
What's actually true: Mating is random only when who pairs with whom has nothing to do with genotype, even if meetings are by chance.
- Random mating means any two individuals are equally likely to pair, whatever their genotypes at the gene you're studying.
- If the mates you can reach, or prefer, tend to share your alleles, like pairs with like. That's nonrandom mating, even when meetings are by chance.
- It gives more homozygotes and fewer heterozygotes than p², 2pq and q² predict. On its own, it doesn't change allele frequencies.
On the exam: Ask if genotype affects who pairs with whom. If it does, even through where they live, mating is nonrandom.