Genetic variation can be introduced into a population by: a) mutation in an individual's genetic code
b) the bottleneck effect
c) the selection of the fittest individuals in the population
d) a new allele arising from a single mutation in a gene.

Punnett squares are used to show possible combinations of alleles or to predict the probability of a trait occurring in offspring. an incomplete dominance cross is performed between a bird that is homozygous for red feathers and a bird that is homozygous for blue feathers. purple offspring result. then, two of the purple offspring are crossed. according to the punnett square for this cross, how many of the offspring from the second cross will have a feather color that results from incomplete dominance? 1 in 4 2 in 4 3 in 4 4 in 4