The problems and interesting facts about breeding poultry
autosomal trait :- a gene carried on a non-sex chromosome and present in two copies in both sexes.
sex-linked trait - a gene carried on the sex chromosome that is present in both sexes; one copy in one sex, two in the other. In mammals, this is the X chromosome (one copy in males, two in females).
In birds, this is the Z chromosome (one copy in females, two in males).
1. 1 st cross
(female)nonbarred x (male)barred -------- all barred
Therefore …….. nonbarred is recessive
2. Reciprocal cross
(female)barred x (male)nonbarred --------(female)nonbarred and (male)barred>
genotype : (female)Z B - W (barred) x (male)Z b - Z b (nonbarred) gives
1 ZBW : 1 ZBZb
ZbW is a nonbarred female (remember the female is heterogametic in birds)
ZBZb is a barred male
From this mating sexing chicks at birth is possible.
For the mating, ZBW x ZbZb, the progeny genotypic ratio is :
For the mating, ZBW x ZBZb, the progeny genotypic ratio is :
The difference is readily apparent and allows large numbers of male and female chicks to be separated quickly with a minimum of labor. Breeders must maintain genetic uniformity for the pertinent alleles in their male and female parent lines, to take advantage of the opportunity to feather-sex chicks.
a - Where trait exists in only on one of the two sexes can occur at single-locus level (long feathers in chickens)
example: feather length in chickens
females all have short feathers
in males, s+s+ and s+s = short feathers
ss = long feathers
click here to see a picture of the difference in feathering
b - more common at the multiple-gene level involving complex traits (e.g., egg laying)
A. Expression of a phenotype is limited to one sex
B. Gene is NOT on a sex chromosome
C. Example – domestic fowl tail and neck plummage.
In the males, cock-feathering is more long and curved, while in the female, hen-feathering is more short and rounded.
S > s : silver > gold
Parents: SS Male x s- Female
F1 Progeny: Ss and S- offspring all silver
ss Male x S- Female
F1 Progeny: Ss silver males
s- gold females
Parents: dw dw x DW-
F1 Progeny: DW dw Male and dw - Female
Application: normal sized Male x dwarf females
The dwarf gene has pleiotropic effects:
• 20% smaller body weights
• 20% less feed consumption
• less eggs
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This site is being created and maintained by
Jill Bowis of Kintaline Poultry and Waterfowl Centre, Benderloch, OBAN Argyll PA37 1QS Scotland
for the utility poultry breeders everywhere
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