Written by the Sellers family of Brookings, South Dakota

The third part of this series - if you haven't already, please read the first part and the second part to cover the basics and get you to this level

Autosomal Genes	Symbol	Comments
Autosomal barring	Ab	Non-sex-linked barring. Sometimes called 'parallel pencilling'. This is not a real gene, rather autosomal barring is due to combinations of Pg, Co, Db with eb, ER, and ebc. See text.
Breda combless	bd	Recessive. Birds with this gene are almost completely lacking comb and wattles. Females are considered to be completely combles and males have a tiny comb.
	Bd+	Dominant, wild-type gene. Lack of breda combless trait. It is believed that this gene is necessary for chickens to produce a comb.
Blue	Bl	Incompletely dominant. Andalusian blue-dilutes black: blue pigment is a modified black. Two nigrum genes, E, and one Bl gives a blue chicken; two Bl genes gives splash.
	bl+	Wild-type gene. Recessive. Lack of blue eumelanin dilution gene, Bl.
Brachydactyl	By	Dominant. Abnormally short digits (toes).
Recessive white genes	c	Thought to give a cleaner white than dominant white. Varieties of White Plymouth Rock, Wyandotte, Minorca, Orpington, Jersey Giant, Dorking, Langshan, Silky and others often carry recessive white genes. Many varieties carry both dominant and recessive white. Allows dark eyes. Pigmentation in chick down varies.
	cre	Recessive white allele that allows red eyes.
	ca	Autosomal albinism. Alellic with the recessive white genes. Evident via lack of eye pigment. Some melanin present in chick down.
	C+	Wild-type gene. Dominant. Lack of recessive white mutations.
	Comments about the C locus	The order of dominance among the recessive white alleles is: C+>c>cre>ca. The presence of other pigment inhibiting or enhancing genes will influence the chick down color. Some adults have a grey color.
Champagne blond	Cb	Dominant. Inhibits pheomelanin (red / gold). The presence of the gene is not observable on the wild-type down
	cb+	Wild-type gene. Recessive. Lack of chanpagne blond dilution.
Columbian	Co	Incompletely dominant.Confines black to hackle and tail in both sexes (called Columbian restriction). Thought to cause a gradient in color from head to tail. Modifies Wheaten to Buff Columbian. Has no effect on extended black, E.
	co+	Wild-type gene. Lack of Columbian restriction. Recessive.
Red diluter	Di	Dominant. Dilutes red, changes red to buff.
	di+	Wild-type gene. Lack of red diluter. Recessive.
Dark	Dk	A proposed gene of an allelemorphic series that darkens the shade of red. Pheomelanin enhancer(s). Dkl was proposed for the dark brown Leghorn and dk+ for the wild-type allele.
Ginger	Gr	This gene may be Columbian, Co, or closely related. This may not be a distinct gene.
Grey	no symbol	Recessive, dilutes black to brown/grey.
The E-locus alleles	E	Often called 'extended black', 'nigrum' or 'self black'. Extends black, changes red to black, red inhibitor.
	ER	Birchen. Resembles extended black, E, but with non-black breaks on head and hackle. Body is black with some stippling (flecks/dots) of other color. Used as red inhibitor in Leghorn.
	eb	Partridge (brown). Sometimes represented as ep, females have non-salmon breast with stippling. Males are wild-type.
	eWh	Dominant wheaten. Female body varies from light salmon to wheat color, some black may be present. Males are wild-type.
	e+	Wild-type. Female: breast is salmon brown and devoid of stippling, body is black and brown in stippled pattern. Males: black breast and abdomen; non-black hackle, saddle and wings.
	es	Speckled. Resembles eb but with less pronounced stippling. Males are wild-type.
	ey	Recessive wheaten. Female: resembles dominant wheaten with more coarse black stippling on breast and back. Males are wild type.
	ebc	Buttercup allele. Resembles the eb phenotype.
	Comments on E-locus alleles	The order of dominance among the generally accepted E-locus alleles is: E>ER>e+>eb>es>ebc>ey. The birchen allele is incompletely dominant to dominant wheaten and the wild-type alleles. Additional alleles have been proposed for the E-locus but research to verify these as separate alleles has not been done. As of this writing, the buttercup allele has been sequenced and has been found to be the same sequence as the eb allele. The buttercup phenotype then is due to modifiers or interactions with other genes. Every E-locus allele influences adult female phenotype. However, all the adult male phenotypes are the same as wild-type except for extended black and birchen.
Ear tuft	Et	Dominant. Lethal in homozygous state. Thought to be associated with birth defects, particularly in the ear structures.
	et+	Wild-type gene. Recessive. Lack of ear tufts.
Erminette	no symbol	Black spots and flecks, variable black and white feathers, similar to pied.
Fibromelanosis	Fm	Dominant. Sounds like a disease. The name was suggested by F. Hutt in the 1940s to emphasize the association with connective tissue pigmentation. This gene is responsible for the deep skin pigmentation of silkie. Fm is strongly influenced by dermal melanin inhibitors such as the sex-linked Id mutation.
	fm+	Wild-type gene. Recessive. Lack of fibromelanosis.
Long tail	Gt, mt	The Gt gene (dominant) allows continual growth of tail and saddle feathers. The mt gene allows certain tail and saddle feathers to be nonmolting.
Henny plumage	Hf	Dominant. The term comes from 'hen feathering' in which male plumage is indistinguishable from female plumage.
	hf+	Wild-type gene. Recessive. Lack of henny feathering.
Cream	ig	Dilutes red. Recessive. A major pheomelanin dilution gene. The gene symbol derives from "inhibitor of gold".
	Ig+	Wild-type gene. Dominant. Lack of cream dilution.
Lace	Lg	This is not a real gene. See text. Partridge Rock, Silver Pencilled Rock.
Beard-Muff	Mb	Incompletely dominant. Characteristic of Ameraucana, Easter Egg Chickens (faux-Araucana)
	mb+	Wild-type gene. Recessive. Lack of beard-muff.
frizzle modifyer	mf	Recessive. Reduces/modifies the effect or expression of the frizzle gene. This gene can modify frizzle heterozygote expression to the point that they are almost indistinguishable from the wild type. Modifies the extreme expression of the frizzle homozygote.
	Mf+	Wild-type gene (uncertain). Dominant. Lack of frizzle modifyer.
Recessive melanotic	mi	Enhances black, (helps) change red to black. E + mi gives a black chicken.
	Mi+	Wild-type gene. Dominant. Lack of recessive melanotic enhancing.
Mottle	mo	Recessive. Makes a white tip on end of feather. Changes a black bird to Mottled and a Buff Columbian to a Mille Fleur. Dilutes epidermal melanin. There may be several alleles corresponding to this locus or non-allelic modifying genes.
	Mo+	Wild-type gene. Dominant. Lack of mottling.
Mahogany	Mh	Dominant. Mahogany restricts eumelanin and enhances the color of red. Rhode Island Red is a good example. Restricts black in the back and wing of both males and females. Down color seemes to be unaffected by mahogany.
	mh+	Wild-type gene. Recessive. Lack of mahogany.
Pink-eye dilute	pK	Dilutes both feathers and eye color. Recessive.
Recessive polydactyly	po-2	Recessive. A number of extra toes can be present even ascending the shank. Associated with leg deformities, significant decrease in hatchability and much higher post-natal mortality.
Feathered legs	Pti-1, Pti-2, Pti-1B, Pti-1L	Dominant. Two different feathered leg loci with perhaps four alleles for the Pti-1 locus (Pti-1, Pti-1B, Pti-1L and pti-1+ : one should always assume the wild-type allele although not always mentioned). Research has shown that the Pti-1 and Pti-2 genes are most likely not allelic (they belong to different loci of the chromosome). When both Pti-1 and Pti-2 alleles are present, heavy feathering as in Cochin, Sultan, Belgian d’Uccle results. If only one is present, the feathering is weaker as in Langshan, Faverolle, Breda. These genes demonstrate a dose effect. Regarding the Pti-1B and Pti-1L genes, the following is from Somes' 1992 paper in Poultry Science: "The Langshan and Brahma breeds were both shown to possess the same single shank-feathering locus, but because of their differences in phenotype and penetrance in the genetic crosses it was suggested that they possessed different alleles at this locus. This locus was designated as Pti-1, with Pti-1L being the Langshan allele and Pti-1B the Brahma allele. The Brahma allele was shown to be dominant over the Langshan allele. Both the Sultan and Cochin breeds were shown to possess two shank-feathering loci, and the data suggested that one of the loci in the Sultan contained the Pti-1L allele. It is hypothesized that the comparable allele in the Cochin breed was Pti-1B. It is proposed that the second locus in both of these breeds is similar, and the symbol Pti-2 is suggested."
Recessive feathered legs	pti-3	The recessive leg feathering gene was identified in a Russian breed referred to as the Pavlov breed. Test matings confirmed the recessive nature of this gene.
Dominant Rumplessness	Rp	No coccyx (tail vertebra), reduces hatchability.
	rp+	Wild-type gene. Recessive. Lack of dominant rumplessness. Fowls usually have tails.
Recessive Rumplessness	rp-2	A skeletal mutation commonly called 'roachback'.
Red spash white	rs	Recessive. Two copies of this gene give a white bird with spashes of red and black. Chicks are white with a red head spot. This gene may be extinct now. It was first isolated in a line of Rhode Island Reds, but it was not maintained nor has it be re-identified.
Recessive black	sg	Not much is known about this gene. Eumelanin intensifier. There may be a number of genes that play this role.
Spurlessness	sl	Recessive. Fowls have no spurs.
Snow-white down	sw	Recessive. The chick down is white rather than yellow.
Vulture hocks	v	Recessive. Long and stiff feathers on the posterior area of the tibia. Characteristic of Belgian Bearded d'Uccle, Breda, Sultan.
Dorking white	wh	Recessive.
Woolly	wo	Recessive.

Glossary

Allele - One of a number of possible alternative forms of genetic information at a gene locus [1].  A member of a set of genes that all have the same location on a given chromosome.  For example, extended black and birchen are allelic genes ( to each other) because they are both found at the E locus or location.

Epistasis - suppression of the effect of a gene by a nonallelic gene [3].  A gene for trait A somehow having an effect on triat B is an example of  epistasis.

Gene - The unit of heredity [1]. A piece of DNA in a chromosome that contains the coded information for a trait.

Generation notation - The original members of a mating are referred to as the parental (P) generation.  The first generation of progeny from the parental cross is referred to as the first filial generation, F1.  The progeny of a cross in which one or both of the parents are from the F1 generation is an F2 generation (F1 x F1 = F2) and so on [1].

Heterosis - The deviation between the cross and midparent means [2].  The difference in some property, for example rate of lay, between a cross bred line and the average for the parent lines.  For example, “hybrid vigor” can be thought of as an effect of heterosis.

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