What is the Extension (E) locus, and what do eb, E and the other e-alleles mean?
The Extension locus is the master control for the black/red balance in plumage — its gene is MC1R.2 Rather than two alleles it carries a whole series, ranked from most to least dominant: E (extended black) > eR (birchen) > EWh (wheaten) > eb (brown/partridge) > e+ (wild-type/duckwing).1 Each sets a different starting distribution of eumelanin (black) versus pheomelanin (red/gold): E extends black over the whole body and suppresses red/gold; eb restricts black to feather edges so a gold-brown ground shows through — the common Partridge base; e+ is the ancestral duckwing. A bird carries two E-alleles and generally shows the higher-ranked one. So eb is not special — it is just one member of the series that happens to underlie many familiar partridge and laced varieties. Full walkthrough in the guide →
What is the difference between Splash and Paint chickens?
They can look similar but come from different genes. Splash is two copies of the Blue locus (Bl/Bl): Blue dilutes black with incomplete dominance, so one copy gives blue-grey and two copies give the pale, blue-flecked Splash. Paint is the Dominant White gene (I) — gene PMEL173 — layered over a Blue or Splash base; Dominant White inhibits eumelanin with a single copy. Because they reach a similar look by different routes, they breed very differently. The Compare Standards tool has a Splash vs Paint preset that puts both standards side by side.
What is the difference between the Lavender gene and the Blue gene?
Both lighten a bird, but they act on different pigments and inherit differently. Blue (Bl) is incompletely dominant and dilutes only eumelanin (black) — red and gold areas keep full colour; one copy blue-grey, two copies splash. Lavender (lav, also called self-blue) is recessive and dilutes both pigments evenly — pale grey where black would be, straw where red/gold would be; its gene is MLPH.4 The visual tell is the red/gold: full and bright on a Blue bird, washed-out on a Lavender bird. And because Lavender is recessive it travels hidden through carriers, whereas a single Blue allele is always visible. More in the guide →
What is the difference between Dominant White and Recessive White?
Both give a white bird, but they are unrelated genes that work oppositely. Dominant White (I) is dominant — a single copy inhibits eumelanin, gene PMEL173; it is also the basis of the Paint pattern over a Blue/Splash base. Recessive white (c) needs two copies to block pigment. Because the underlying genotype can be completely different, two white birds are not necessarily related in how they became white, and crossing them can produce coloured chicks. Full comparison on the white genetics page →
What are sex-linked genes in chickens?
Sex-linked genes sit on the Z chromosome. In chickens it is the female who carries two different sex chromosomes: roosters are ZZ, hens are ZW. So a hen carries only one copy of any Z-linked gene (she is hemizygous) and always shows whatever allele is on that single Z, while a rooster needs two recessive copies to show a recessive trait. The site's sex-linked loci are Silver/Gold (S, gene SLC45A25), Barring (B, gene CDKN2A/B6) and Chocolate (Choc, gene TYRP17). This asymmetry is what lets some crosses produce chicks that can be sexed by colour at hatch — see Sex-linked colour genes for the worked crosses, or the Genetics Guide.
Why do the Compare and Breeding tools sometimes show results separately for roosters and hens?
Most colour loci are autosomal, so sons and daughters inherit them the same way and one set of results covers both. But at sex-linked loci (Silver, Barring, Chocolate — see above) a hen receives only one Z chromosome, from her father, while a rooster receives one from each parent — so offspring ratios genuinely differ by sex there. The Breeding Outcomes tool shows genotype frequencies on a rooster basis and adds a note wherever a cross involves a sex-linked gene, because for those genes "half the offspring" is not the same statement for sons as for daughters.
What is a Punnett square, and what do F1 and F2 mean?
A Punnett square is a grid of every allele combination two parents can pass on, used to read off the expected genotype ratios of a cross. F1 is the first-generation offspring of two parents; F2 is the next generation, from crossing two F1 birds together or an F1 back to a parent. F2 is where recessive traits hidden in the F1 can reappear, which is why breeding projects plan out to F2 rather than judging a cross from the F1 alone. The Breeding Outcomes tool builds the squares and the F1/F2 frequency tables for you.
How many eggs do I need to hatch to get a certain number of chicks of one genotype?
As a planning estimate, divide the number of chicks you want by that genotype's expected frequency from your cross. A genotype expected at about 9.8%, for example, needs roughly 100 hatched eggs to expect around 10 chicks of it. Real hatches vary around the expected ratio, so treat it as a target, not a guarantee. The Breeding Outcomes genotype frequency table has a calculator for this: tick the genotype rows you want, enter how many chicks you need, and it works out roughly how many eggs to plan to hatch.
Should I use "color" or "colour" when searching this site?
Either — the site and its tools use both spellings interchangeably and search is not spelling-sensitive. "Colour" appears more in the body text for an international breeder audience, while "color" is in the site name and some labels. There is no separate content for each spelling.
Where does the genetic and breed standard data on this site come from?
Breed standard descriptions and photos are drawn from chicken-colors.info, a reference built by breeders and geneticists, which itself builds on the Dutch Kippenencyclopedie and on the scientific literature. Standard genotypes used in the Breeding Outcomes calculator come from kippenjungle.nl. The genetics explained here is standard, published chicken colour genetics; specific molecular claims are cited to the primary literature in the Genetics Guide. This site builds interactive tools on top of that reference material and links back to the original standard for every variety shown.
Does this site store my breeding data, photos, or search history?
No account exists. Compare Standards and Breeding Outcomes calculate results live for each request and do not save your inputs, uploaded calculator screenshots, or comparison history anywhere. Breeding Outcomes also lets you optionally save named birds and clans for convenience — these are kept only in your own browser on your device, never reach our servers, are not shared, and are removed when you clear your browser data. The one exception: if you choose to enter your email address to be notified about new features, that email address is stored on our server so we can contact you — it is never shared and used for nothing else.
- Smyth JR Jr (1990) Genetics of plumage, skin and eye pigmentation in chickens. In: Crawford RD (ed.) Poultry Breeding and Genetics. Elsevier — the Extension (E) allele series and dominance order.
- Kerje S, Lind J, Schütz K, Jensen P, Andersson L (2003) Melanocortin 1-receptor (MC1R) mutations are associated with plumage colour in chicken. Animal Genetics 34:241–248.
- Kerje S et al. (2004) The Dominant white, Dun and Smoky color variants in chicken are associated with insertion/deletion polymorphisms in the PMEL17 gene. Genetics 168:1507–1518.
- Vaez M et al. (2008) A single point-mutation within the melanophilin (MLPH) gene causes the lavender plumage colour dilution phenotype in the chicken. BMC Genetics 9:7.
- Gunnarsson U et al. (2007) Mutations in SLC45A2 cause plumage color variation in chicken and Japanese quail. Genetics 175:867–877.
- Hellström AR et al. (2010) Sex-linked barring in chickens is controlled by the CDKN2A/B tumour-suppressor locus. Pigment Cell & Melanoma Research 23:521–530.
- Li J et al. (2019) A missense mutation in TYRP1 causes the chocolate plumage color in chicken and alters melanosome structure. Pigment Cell & Melanoma Research 32:381–390.