Alleles have identity by type (IBT) when they have the same phenotypic effect, or if applied to a variation in the composition of DNA such as a Single nucleotide polymorphism when they have the same DNA sequence.
Alleles that are identical by type fall into two groups; those that are identical by descent (IBD) because they arose from the same allele in an earlier generation; and those that are non-identical by descent (NIBD) because they arose from separate mutations. NIBD can also be identical by state (IBS) though, if they share the same mutational expression (just not origin). Parent-offspring pairs share 50% of their genes IBD, and monozygotic twins share 100% IBD.
Famous quotes containing the words identity and/or type:
“No other group in America has so had their identity socialized out of existence as have black women.... When black people are talked about the focus tends to be on black men; and when women are talked about the focus tends to be on white women.”
—bell hooks (b. c. 1955)
“To put it rather bluntly, I am not the type who wants to go back to the land; I am the type who wants to go back to the hotel.”
—Fran Lebowitz (b. 1951)