Question

In cats, some are black, some are orange, and some are calico (fur that is both black and orange.) All calico cats are always female. This trait represents two inheritance patterns. List which two and explain how you know.

Answer 1

Codominance. This is shown by the calico cats, who have both black and orange phenotypic expression; the black and orange are not mixed like incomplete dominance, and one is not entirely dominant over the other. (A common example is the roan cow, whose fur is a bit red, a bit white.)

Sex-linked inheritance. Since calico cats are said to always be female (which actually isn't entirely accurate, by the way) this means that the coat color is sex-linked. It's found on the X chromosome, so a female cat can have one X black and one X orange chromosome. This is only possible in males when they are nondisjunct and inherit two Xs along with their Y... but that's a completely different story. :)