Dominant/RecessiveMutation.

[Jayd]

A dominant mutation needs only to be present

in one copy of a gene to change a bird's appearance. Normal grey is dominant to all recessive and sex-linked colors. The two true dominant mutations are dominant silver and dominant yellow-cheek. A bird with one dominant silver gene will appear silver, and is called a single-factor bird. A cockatiel with two copies of the gene is called a double-factor. The two forms can be told apart visually; a double-factor is much paler than a single-factor

(think of the double-factor as having inherited a double dose of melanin reduction). Yellow-cheek is inherited in the same way as dominant silver, but single-factor and double-factor birds cannot be visually told apart.

 

A recessive mutation must affect both copies of a gene in order to change the bird's appearance; a visually Whiteface cockatiel must have inherited a copy of the "Whiteface" gene from each of its parents. A bird that possesses only one copy of a recessive gene is called a split, and will pass that mutation on to half of its offspring. Most splits will not show any sign of the hidden mutation, although cockatiels that are split to pied will often have a patch of

yellow feathers on the backs of their necks.

Edited June 12, 2012 by Jayd