Question: What do you get when you mate a-
-normal male and lutino hen?
Answer: All normals.
-pied male and cinnamon hen?
Answer: All normals. -silver male and pearl hen?
Answer: All mormals.
-fallow male and pied-cinnamon hen?
Answer: All normals.
What's going on here? Can't cockatiels produce anything but normals? Well of course they can - when paired according to some basic genetic principles.
The purpose of this article is to introduce a simple, nontechnical method of computing offspring expectations when crossing mutations with normals or other mutations.
A simple listing of expectations is far from being practical. The possible pairings of normals, the six mutations, their splits and double splits total a tremendous number of possible combinations. Yields from some of the pairings are so diverse that memorization is' next to impossible. Some pairings have a possibility of 32 (that's right, 32) genetically different offspring. (An example of this will be demonstrated at the end of this article.)
Besides the familiar normal (gray) cockatiel, to my knowledge there are six mutations: pied, lutino (commonly but erroneously called albino or white), pearl, cinnamon (or Isabel), silver, and fallow. I know of at least two others of which none have been released yet by their original breeders. Combinations of these mutations also exist. Those that I know of are pied-lutino, pied-pearl, pied-cinnamon, lutino-pearl, cinnamon-pearl, and piedcinnamon-pearl. Others may exist, but I have not seen or heard of them.
Because this presentation will be nontechnical in nature, some liberties will be taken in descriptions and definitions. This may cause the competent biologist to have a heart attack or at least palpitations. If we must sacrifice a biologist or two for the sake of clear communication, then so be it.
Let's start out with a few definitions. Genes are the controlling "chemicals" that direct an individual bird to look and act the way it does. They are inherited from the parents and passed on to the offspring thus establishing a pattern passed on from generation to generation. The only genes we are going to concern ourselves with here are those that affect color.
Mutations occur when there is a spontaneous alteration in the genetic code. This alteration took place for each one of the cockatiel color mutations we know.
Chromosomes are the "buckets" in which the genes are carried. The male's sperm and female's ovum both contain many chromosomes each carrying those mysterious genes. Chromosomes are friendly little creatures who detest loneliness. For this reason, they always travel in pairs.
Split is a term used to define a bird which carries the genes of a specific mutation yet does not display the color pattern of that mutation.
Genes for a mutation are inherited by one of two modes - '' simple recesive'' or "sex-linked".
Simple recessive mutations may be reproduced without regard for the sex of the mutant parent. Sex-linked mutations are carried on the male chromosome and offspring from pairings of mutation and normal or other mutation will differ according to which parent is the male and which is the female.
Here are the modes of inheritance for the basic mutations:
Simple Recessive Sex-linked
Pied, silver and fallow are "recessive" to normal; or to put it another way, normal is dominant over these mutations. Hence, crossing a simple recessive with a normal will produce all normal appearing birds (split for the mutation).
Genes which ar responsible for transmitting parental characteristics to offspring are carried on a chromosome. Chromosomes travel in pairs. Conception requires one chromosome from the male parent's sperm and one from the female parent's ovum.
For simple recessive offspring prediction, let's use a capital "N" to denote a dominant normal chromosome and lower case letter for a recessive chromosome ("p" for pied, "s" for silver and "f'" for fallow).
A normal which is not split for any mutation will have the chromosome pairing of NN; a pied - pp; silver - ss; and fallow - ff.
If we mate a normal (NN) with a pied (pp), all offspring will have one chromosome from each parent (one N and one p). Hence, all offspring will be Np- that is, half normal and half pied. However, since pied is recessive to normal, the offspring will be normal in appearance and split for pied. This may be diagrammed as:
One parent's I The other parent's
chromosome pair I chromosome pair Offspring chromosome pairing # I Offspring chromosome pairing #2 Offspring chromosome pairing #3 Offspring chromosome pairing #4
N1 N2 I p1 p2 N1p1