What is complete autosomal dominant inheritance?

• In its simplest form, it involves 1 pair of genes with the wild type gene "p" being recessive to the mutant gene "P" in any combination. If the wild type/natural colour of a bird is purple and the mutant form is yellow, the following will be true:

                + pp = Purple Bird

                + Pp = Yellow Bird

                + PP = Yellow Bird

• In the following example, one gene, we will call it "P", is responsible for colour. The "P" gene comes in 2 forms: "P" and "p". When the "P" gene is a capital "P", it is responsible for the yellow colour and classified as dominant. When the "P" gene is a small "p", it is responsible for the regular/wild type yellow colour and is classified as recessive. The are always 2 copies of the "P" gene in each individual. If an individual is pp, then it is purple/normal/wild type or is a homozygote (the pair of genes are the same) for the purple gene. Purple is the recessive form. If an individual is PP, then it is yellow or in its dominant form. "PP" is a homozygote for the yellow gene. Most autosomal dominant mutations are incomplete, but some are complete (as this one is) meaning that the heterzygote has the same phenotype (or appearance) as the homozygous dominant form (PP). The phenotype for a Pp individual is therefore yellow like the PP individual . It is still a heterozygote, but it appears yellow.

"P" = yellow gene

"p" = purple gene

PP = yellow individual

Pp = yellow individual

pp = purple individual

(1) Yellow (PP) X Yellow (PP) = All Yellow (PP)

	P	P
P	PP	PP
P	PP	PP

(2) Purple (pp) X Purple (pp) = All Purple (pp)

	p	p
p	pp	pp
p	pp	pp

(3) Yellow (PP) X Purple (pp) = All Heterozygotes (Pp)

	P	P
p	Pp	Pp
p	Pp	Pp

(4) Heterozygote (Pp) X Heterozygote (Pp) = 25% Yellow (PP), 50% Heterozygote (Pp), & 25% Purple (pp)

	P	p
P	PP	Pp
p	Pp	pp

(5) Heterozygote (Pp) X Yellow (PP) = 50% Yellow (PP) & 50% Heterozygote (Pp)

	P	p
P	PP	Pp
P	PP	Pp

(6) Heterozygote (Pp) X Purple (pp) = 50% Heterozygote (Pp) & 50% Purple (pp)

	P	p
p	Pp	pp
p	Pp	pp