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The majority of symbols shown here are taken from Dr. Willard F. Hollander’s book, "Origins and Excursions in Pigeon Genetics". I have separated them into groups by their genetic effects and known linkage. The groupings are Sex-Linked Color genes; Autosome (non sex-linked) genes which effect basic color; and Autosome genes that effect body and or feather structure. Within each grouping are also listed their mutant alleles. Genes with the symbol + denote the original wild Rock Pigeon's genes or what we would call a wild type pigeon where no mutant genes are present.
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
for each set.
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
In otherwords one gene for each chromosome in a set of two each.
Other Autosomal genes which effect the basic color but are not found on
the same chromosome as the pattern series and therefore are not linked
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 to be assigned a lower case and all partial dominant, codominant and or dominant genes are assigned capitals.
Brown is a mutation from wild type. The gene changes the basic color from blue to brown but is only displayed when in the hemizygous and or homozygous states. This classifies it as being a recessive. Therefore, the symbol for brown is a lower case letter b.
All Wild Type alleles are denoted by the symbol +. However should we want to be more specific and denote their locus and degree of dominance we would use the mutant's appropriate upper or lower case symbol and add the superscript + to denote wild type.
Since the wild type allele for brown is a codominant, we would assign it the symbol B+. Please keep in mind that the Capital B does not stand for blue but rather an allele at the b locus that is a dominant. In this case a wild type dominant which would result in a blue phenotype should no other associated genes prevent its expression.
BA or ash red is another mutant at the b locus and since it is more dominant than B+ we assign the superscript capital A for ash. Keep in mind the use of the letter b, be it upper or lower case, is for the brown locus and since brown was the first of the mutations to be discovered at this locus it becomes the standard. Had Ash red been the first, then these symbols would have been lower case a for brown, A+for wild type blue and A for ash red. But brown came first so the locus is known as the b locus, not the A locus.
Okay so what is the correct symbol for Ember? First we know that ember is an allele of recessive red (e). Secondly we know that Ember is also a recessive gene since it cannot be expressed in the presence of a dominant. Thirdly we know that in the order of recessive dominances, Ember is more dominant than its allele recessive red. So how do we symbolize it to reflect this know data for Ember?
Answer: Since recessive red has been assigned e as a simple recessive, ember will also have to be assigned the lower case of e. However, since ember is the more dominant of the two recessives it gets the superscript capital E. In the case for ember the proper symbol would then be eE. This tells the reader that the gene is located at the e locus and is a recessive but more dominant than its other allele e at this same locus.
Okay so what do we assign, as a symbol for Wild Type, at this locus should we want to denote its state of dominance? Simple, we would symbolize Wild Type at the e locus as E+. This tells us that Wild Type at the e locus is a dominant gene.
This same is true for all other mutations. Now one last question; What is the correct symbol for non spread if spread is symbolized as being S.
Answer : 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 in any language, words have meanings. The same is true in genetic science where standard symbols are used so that others can read and come to the same understanding.