All genes symbolized with an upper case letter are dominant to some degree. All recessive genes are symbolized in lower case. This case distinction between the dominant and recessive types is a standard practice. It serves as an aid in keeping them classified properly in your mind while you are working with them.
Just remember, if its listed as beginning with a capital letter, it's a dominant gene. A dominant gene will express when present. The only exception to this rule is when it is being masked by another genetic condition. Symbols beginning with lower case letters are always recessive. A recessive gene can only be displayed when in their pure state.
These are the Sex-Linked genes. They occur on the sex or Z chromosome, of which a cock has two and a hen only one. Remember each Z chromosome will carry only one of these possibilities for each set.
The four Color Dilution possibilities are:
D+ - Wild Type for Full color
The three Color Reduction possibilities are:
R+ - Wild Type for nonreduction or Full Color
There is also a Lethal Sex-Linked gene that occurs on the sex or Z chromosome which is known as Lethal Sex-Linked web-foot or simply Weblethal. It's two possibilities are:
Wl+ - Wild Type for non weblethal or NormalWe also have the Almond family (no I don't mean the singers but the genes that causes the scrambled, speckled patchwork of colors) which occurs on the Z chromosome. Originally known as gesprenkelt which means sprinkled in German is now known to consist of the following mutations:
St - Almond
Genes "not found" on the sex or Z chromosomes are known as Autosomal genes. Since they occur on non-sex chromosomes every bird, both cocks and hens will carry two gene possibilities for each chromosome set. In otherwords one gene for each chromosome in a set of two each.
Other Autosomal genes which affect the birds basic color but are not found on the same chromosome as the pattern series and are therefore not linked to the pattern are listed below. Their wild-type or normal alleles are not included:
al - albino
Other Autosomal genes which affect both body and or feather structures are listed below. Their wild-type or normal alleles are not included here:
ac - Lethal
In genetics we use symbols to denote the various gene mutations for each chromosome locus. Unfortunately, we do not know how many actual locus points there are. Nor do we know all of the mutations that exist since not all mutations have something physical for us to point to as a means of identification. We know that all genes act in one of three ways.
1) If "recessive" they will not be express when in combination with a dominant allele.
2) If "partial dominate" or "codominant" they will express themselves partially or to some degree when heterozygous. When homozygous or pure they will be express completely. Let me use grizzle to demonstrate what is meant by partial dominate or codominance. A single gene for grizzle on a genetically blue bar bird would give the typical salt and pepper looking phenotype with black bars, black salt and peppery head, white salt and peppery body and black wing tips. This same gene in its pure or homozygous state would be almost completely white with only a small amount of black peppery effect around the bird’s head and black wing tips. Other examples of partial dominate codominant genes being, Almond, Indigo, and Dominant Opal to name a few.
3) If "dominant" they will be fully express regardless of heterozygous or homozygous states. An example being Spread.
When we select a symbol to denote any new mutation we try to incorporate as much of this information into the symbol as possible. To do this all mutations are given a letter or set of letters to denote their name. In addition, this becomes the name of the chromosome's locus point where the mutant gene is to be found. Next to we assign a upper or lower case first letter to denote whether the new mutant is a recessive or a dominant gene.
All recessive genes are assigned symbols in a lower case to denote their being a recessive, while all partial dominant, codominant and or dominant genes are assigned symbols beginnibg with upper case capitals to denote their being a dominant form.
This same is true for all the other mutations. Now one last question. If Spread is symbolized as being S, what is the correct symbol for non spread? Answer : Lower cass s with superscript + or in this case..... s+. Now can you explain or figure out why it's a lower case s with the superscript +? If you can, then you understand correctly the use of symbols in pigeon genetics. It’s not a case of what I or someone else personally think works well. It's simply a standardize format of rules. Like all language, words must have set meanings. The same is true in genetic science where standard symbols are used so that others can read and come to the same understanding.
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