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The concept of an auto-sexing breed of chicken is due to the geneticist Reginald Punnett, who during the First World War had already proposed the technique of cross-breeding chickens carrying the barred gene (B) with others to produce sex-linked chicks with plumage differences that could easily be distinguished.
The chicken breeds recognized by the American Poultry Association are listed in the American Standard of Perfection. They are categorized into classes: standard-sized breeds are grouped by type or by place of origin, while bantam breeds are classified according to type or physical characteristics.
All chickens lay eggs, have edible meat, and possess a unique appearance. However, distinct breeds are the result of selective breeding to emphasize certain traits. Any breed may be used for general agricultural purposes, and all breeds are shown to some degree. But each chicken breed is known for a primary use.
Dwarfism in chickens has been found to be controlled by several simple genetic factors. Some types are autosomic while others are sex-linked, but when poultry breeders make reference to 'dwarf chickens' they usually refer implicitly to sex-linked recessive dwarfism due to the recessive gene dw, located on the Z chromosome.
Breeding increased under the Roman Empire and reduced in the Middle Ages. [65] Genetic sequencing of chicken bones from archaeological sites in Europe revealed that in the High Middle Ages chickens became less aggressive and began to lay eggs earlier in the breeding season. [72]
Hen-feathering in cocks is one of the typical characteristics of the Sebright Bantam, a breed established circa 1810, in accordance with the intentions of its creator, Sir John Saunders Sebright. Sexual dimorphism in plumage is very common in birds, [ 1 ] particularly within Phasianidae where males are bigger and have brighter and more colorful ...
The ISA Brown is a crossbreed of chicken, with sex-linked coloration.It is thought to have been the result of a complex series of crosses including but not limited to Rhode Island Reds and Rhode Island Whites, and contains genes from a wide range of breeds, the list of which is a closely guarded secret. [1]
The B1 allele is causing the typical sex-linked barring phenotype/ appearance and is present in most modern sex-linked barred chicken breeds. Females or male chickens carrying the B2 allele in the heterozygous condition show a defined barring pattern but in the homozygous condition, males are essentially white with very little pigmentation. [9]
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