there are sex-linked genes- chromosome named "Z". Males carry two Z chromozomes (ZZ), and females carry one (ZW). Barring, Silver, and the Bantam gene are carried on Z. All males are ZZ and all females are ZW. Since all offspring that inherit a "Z" from both the female and the male will be male, only the male's chromosome will be in the female offspring, since the female sent a "W" which does not carry the sex-linked gene. Therefore, the sex of the chick is determined by which chromosome the female donates and the female offspring will always inherit the father's "Z" chromosome. The male offspring will all get a "Z" from both the male and the female.
Clear as mud ?
For example: A Birchen male (carries 2 Silver alleles also written s+/* --she has a Z chromosome carrying a gold allele and a "W" chromosome without a color specification).
OFFSPRING: females will be 100% silver, males will be 100% mixed silver and gold.
** In the above cases, I would like to mention that we are not accounting for any of the additional genes that make a Gold Birchen into a Black Copper (such as Mahogany, etc.) which you would lose or greatly dilute when crossing.
Five eye colors found in chickens: pearl, red, brown, black and pink (albino).
Eye color is affected by age, genetics, diet and diseases.
Eye pigment is determined by three pigments: Black from same melanin pigment that makes feathers black, yellow from carrotenoid pigment xanthophylls, & red from haemoglobin in blood’s red corpuscles. When there is no black or yellow, iris is bright red from seeing blood vessels.
Condition known as “hen’s eye” is due to loss of iris pigment from laying eggs.This helps explain why great laying hens seem washed out as laying progresses; color loss in legs, combs, wattles, beak, eyes, skin, etc.
Be warned!!! Selection for proper eye colorations should not be overlooked past simple compliance to the poultry standards. Eye color is an indication of age (young chicks have what is called “bull eyes,” dark eyes up until about 8 weeks of age), gender (adult males have higher ratio of red corpuscles to white, so iris tends to be deeper red than corresponding females), AND health. Marek’s (one form of this disease affecting eyes; cloudy greyish, dilated, irregular pupil; distorted or blinded eye) and fowl paralysis are sometimes accompanied by iris color degeneration. Cull from your breeding prospects and do not breed from off coloured irises unless you are raising breeds that require something like pearl colored eyes as listed in their SOP description.
When an eye turns to grey-green, it can be a sign of cancer (ocular lymphomatosis). This kind of cancer produces a large number of fluid filled cells that by their presence, obscure the sharp contrast of iris and pupil and/or pigment of the iris. This blocking of seeing inside the eye may happen rapidly, slowly, in one or both eyes, and helps explain why sometimes, one eye is affected, and not the other. Stress may incite the condition to become more evident, simple stress from sexual maturity, moulting, laying, etc. The eye color becomes exactly the same as seen in young chicks prior to maturing into adult like pigmentation.
There is an old saying Dr. Carefoot quips in his book “Creative Poultry Breeding” about breeding from older birds, “Never breed from pullets, themselves from pullets bred.” He quotes this when talking about selecting birds to breed from (hens or at least pullets that have survived the stresses of having gone broody or one moult cycle) and thereby avoiding iris degeneration since it is associated with cancer and big liver diseases. Trouble comes in the dark eyed breeds where lightening of the iris cannot be detected so readily and thereby explains why in some inbred lines of Sebrights, large OEG and Silkies, they have issues with Marek’s. Can’t cull against eye cancer by observing changes in iris colourations in black eyes! VBG