Mutations can be a single change from one nucleotide to another, an insertion or deletion of a single nucleotide, or of many nucleotides.
Mutations can include translocations of parts of chromosomes, inversions, duplications.
Sources of Variation Recombination can combine genes and alleles in unique combinations. When a transposon lands near a gene, it can alter the level or pattern of gene expression. Unequal Crossing Over. Can differentiate homology from analogy Mutation Rates Most genes mutate at a very low rate. Even a low mutation rate can create many new mutant alleles because in a large population, each of the large number of genes is at risk to mutate.