Chicken Colour Genetics Glossary

Eumelanin

The pigment that produces black and dark-brown colour in a feather. A large share of colour genes act by moving, restricting, or diluting eumelanin. In the guide →

Pheomelanin

The pigment that produces red, gold, and buff. It shows as the "ground colour" wherever eumelanin has been kept out. In the guide →

Gene

A stretch of DNA with a specific job — here, a job affecting where and how pigment is deposited.

Locus (plural: loci)

The physical place on a chromosome where a gene sits. "Locus" names the location and gene; "allele" names a specific version found there. In the guide →

Allele

One version of a gene. A bird holds two alleles at every autosomal locus — one inherited from each parent. At the Blue locus, for example, Bl and bl+ are two alleles.

Genotype

The actual pair of alleles a bird carries at a locus (e.g. Bl/bl+).

Phenotype

What the bird actually looks like. Two birds can share a phenotype while carrying different genotypes — a central reason breeding results can surprise you. In the guide →

Wild-type

The ancestral reference allele at a locus, written with a "+" (e.g. e+, bl+). A notation baseline — not necessarily the commonest allele in a modern breed.

Ground colour

The underlying pheomelanin colour of a feather, over which any pattern of eumelanin is laid.

Homozygous

Carrying two matching alleles at a locus (bl+/bl+ or Bl/Bl).

Heterozygous

Carrying two different alleles at a locus (Bl/bl+). A recessive allele can travel hidden in a heterozygote.

Hemizygous

Carrying only a single copy of a gene. Because hens are ZW, they are hemizygous for every sex-linked (Z-linked) gene — whatever sits on their one Z is what they show. In the guide →

Dominant

An allele that shows its effect with just one copy. "Dominant" describes how many copies are needed to see it — not that the allele is stronger or better. In the guide →

Recessive

An allele that shows its effect only when both copies are present.

Incomplete dominance

Inheritance in which the heterozygote is visibly intermediate rather than matching one homozygote. Blue is the classic case: black → blue-grey (one copy) → splash (two copies), giving a 1:2:1 ratio. In the guide →

Autosomal

On a chromosome other than the sex chromosomes (Z/W); inherited the same way by both sexes.

Sex-linked (Z-linked)

On the Z chromosome. Roosters are ZZ and hens are ZW, so these genes are inherited differently by sons and daughters — the basis of colour-sexing. Sex-linked genes page →

Epistasis

When one gene's visible effect depends on the alleles present at another gene — for example, a pattern gene meaning different things on different Extension bases. It is the main reason a gene cannot be read in isolation. In the guide →

Punnett square

A grid of every allele combination two parents can pass on, used to read expected offspring ratios. The Breeding Outcomes tool builds these for you.

F1 / F2

F1 is the first-generation offspring of a cross; F2 is the next generation, from crossing two F1 birds — where recessives masked in the F1 can reappear.

Linked genes & recombination frequency

Genes close together on one chromosome are usually inherited together; the recombination frequency is the chance a crossover separates them. The Db–Ml–Pg group is linked (≈0.12 Db↔Ml, ≈0.10 Ml↔Pg). In the guide → · Linked genes page →

The genes the Compare and Breeding tools work with. Verified molecular gene identities are noted where established; see the guide's references for sources.

E — Extension

The master control for the black/red balance, and the base every variety starts from. It carries a whole series of alleles ranked E > eR > EWh > eb > e+ (extended black, birchen, wheaten, brown/partridge, wild-type duckwing). Its gene is MC1R. In the guide →

Co — Columbian

Sweeps eumelanin off the body, confining it to the hackle, tail, and wing tips — the "Light"/Columbian look. In the guide →

Db — Dark Brown

Deepens the pheomelanin ground toward darker ocher and red-brown shades. One of the linked Db–Ml–Pg group. In the guide → · Linked genes page →

Pg — Pattern gene

Organises eumelanin into structured markings. Its result depends on context: with eb+Co it gives lacing, with eb+double Ml double lacing, and with eR spangling. A textbook case of epistasis. In the guide →

Ml — Melanotic

Pushes eumelanin further through the plumage, darkening the bird. Part of the linked Db–Ml–Pg group. In the guide → · Linked genes page →

Cha — Charcoal

Dilutes eumelanin toward a dark grey.

Mh — Mahogany

Intensifies pheomelanin into a deep mahogany red.

Di — Dilute

Dilutes both pigments, lightening the whole bird.

Ig — Inhibitor of Gold

With two copies (ig/ig) it allows a gold or buff ground to show.

Cb — Champagne Blond

Lightens pheomelanin toward pale buff or cream.

S — Silver / Gold (sex-linked)

The S allele suppresses pheomelanin, replacing a gold ground with silver/white. Its gene is SLC45A2. Being Z-linked, it behaves differently in the two sexes. In the guide →

B — Barring (sex-linked)

Lays repeating transverse white bars across each feather — the cuckoo/barred pattern. Its gene is CDKN2A/B. In the guide →

Choc — Chocolate (sex-linked)

Dilutes eumelanin to a warm chocolate brown. Its gene is TYRP1. Chocolate page →

I — Dominant White

Inhibits eumelanin with a single copy, turning a coloured base largely white; layered on a Blue/Splash base it gives the "Paint" pattern. Its gene is PMEL17. Unrelated to recessive white. White genetics page →

Bl — Blue

Dilutes eumelanin with incomplete dominance: one copy gives blue-grey, two copies splash. Leaves pheomelanin untouched. Blue, Splash & Black page →

Lav — Lavender (self-blue)

A recessive that dilutes both pigments evenly — pale grey where black would be, straw where red/gold would be. That both-pigment action is the key difference from Blue. Its gene is MLPH. Lavender page →

Mo — Mottling

A recessive (mo/mo) that tips feather ends with white V-shaped spots — the basis of mille fleur and mottled varieties.

C — Recessive White

A recessive that blocks pigment when present in two copies, reaching white by a completely different route than Dominant White (its gene is tyrosinase, TYR). Two white birds are not necessarily "the same" underneath. White genetics page →

The visible results — the words that describe how pigment is arranged on the finished bird, and that appear throughout the Compare tables.

Self / solid

A single, even colour over the whole bird, with no pattern — e.g. self-black or self-blue (lavender).

Partridge

The brown-based (eb) pattern: a gold/brown ground with black restricted to markings and feather detail.

Duckwing

The wild-type (e+) pattern of the ancestral jungle fowl, with its characteristic black-and-gold distribution.

Birchen

A largely black bird (eR base) with restricted silver or gold left in the hackle and saddle.

Wheaten

An EWh-based pattern in which red/gold dominates — strikingly so in the hen, while the rooster keeps black in breast and tail.

Columbian

The clean pattern produced by the Co gene: a white or gold body with black confined to hackle, tail, and wing tips.

Barred / cuckoo

Repeating transverse white bars across each feather, produced by the sex-linked B gene ("cuckoo" is the term for the softer-edged version).

Lacing

A clean dark border of eumelanin running around the edge of a feather of ground colour. Double lacing has two concentric borders. Pattern genes page →

Pencilling

Several fine, concentric lines of eumelanin across each feather, as in Partridge Wyandotte hens.

Spangling

A single dark spot or crescent at the very tip of each feather.

Mottling

White V-shaped tips on the feathers (from mo/mo); combined with a coloured ground it gives mille-fleur-type patterns.

Blue

The one-copy Bl phenotype: eumelanin diluted to an even blue-grey, red/gold areas unchanged.

Splash

The two-copy Bl phenotype: a pale bird irregularly flecked with blue-grey.