If an A1 allele is higher in frequency than the population
It will continue to increase in frequency
If an A2 allele is lower in frequency than the population
It will decline in frequency
When A1 is dominant and A2 deleterious recessive
A1 will always increase and mask the recessive
If delta p is negative
The allele is decreasing in frequency
If delta p is positive
The allele is increasing in frequency
Equilibrium
The point where we do not expect frequencies to change
Nontrivial equilibrium
Selective forces are equal; 0 and 1
McDonald-Kreitman
If most replacement substitutions are advantageous rather than neutral, they will increase in frequency and be fixed more rapidly than by genetic drift alone
Selective sweep
Rapid fixation of allele, more recently coalesced, positive selection
If you have drift only, with variation maintainted
There will be no linkage disequilibrium
Positive selection
Reduces variation at closely linked sites
Balancing selection
Overdominance; selective maintenance of multiple lineages; greater variation; older than alleles under drift
Background selection
Eliminates neutral variation that is linked to deleterious mutations.
Example of balancing selection
Human-Chimp MHC: the loci of chimp and human allele more closely related to one another.
Chip Aquadro
Sequence analysis of adh genes on fruit flies, compared multiple sequences discovered that linkage and selection combined increase genetic distance therefore selection favors both alleles. Greater genetic variation
Example of evolution in our lifetime
Boston betularia, industrial Melanism, wild type was grey, but with industrial revolution it mutated to black, then went back to grew when factories were cleaned up.