Basic genetics: creatures that have two parents (such as mammals and birds) have two copies of most of their genes. They inherit one copy from their mother and the other from their father. There are a few genes that are called sex-linked because of the nature of the chromosome that distinguished between male and female.
In birds the males have two long chromosomes designated Z. The females have one long Z chromosome and a shorter W chromosome. For mammals the chromosomes are X & Y, and it is the females that have two of the same.
Anyways, with birds, females have only one copy of the sex-linked genes--they are the genes on the Z chromosome that are past the end of the W chromosome.
Okay--all those letter: each gene is designated with a name, and the letters are essentially abbreviations for that name. Co is for columbian, S is for silver, lav is for lavender, etc. Notice that I capitalized Co and S, but not lav. That too means something. Capitalized gene abbreviations indicate a dominate gene (or more specifically the dominant "allele" for the gene. An allele is one of the variations that a gene can have: Co is columbian, co+ is not-columbian; Bl is blue, bl+ is not-blue. The + indicates that that allele is "wild-type," the allele on carried by the red jungle fowl, the "proto-chicken."
There are several ways of indicating a gene pair:
a slash (or sometimes two) between each: I/I or I//I
simply listing them together with or without a space: II or I I
in parentheses with a comma separator: (I,I)
All of these indicate that the bird has two copies of the same allele, I, aka dominant white. When a bird has two copies of the same allele, it is homozygous. It the two copies are not identical, it would be heterozygous. Here are some examples of heterozygous genes: Ii+ Bb+ Ss+
If you go back to the chicken calculator and click on each gene you will see the various alleles available and names for the gene and some allele combinations. Play with that awhile and come back with more questions
Suze
