Author Topic: Dominant White in Poultry  (Read 319 times)

Lindsay Helton

  • Administrator
  • Ameraucana Guru
  • *****
  • Posts: 928
    • View Profile
Dominant White in Poultry
« on: March 03, 2022, 08:46:50 PM »
Several scientific studies completed in the early 1900s, including those by Bateson (1902), Hurst (1905), and Hadley (1913), found that the white Leghorn carries an autosomal gene capable of inhibiting the development of black pigment in plumage. When white Leghorns were crossed with breeds that have solid black plumage, the offspring produced were predominantly white.

Hadley (1913) designated this gene as “I” (inhibitor of black pigment), otherwise known as the Dominant White gene.

Hadley found that in the case of Dominant White, the genes necessary for black pigment are present but do not manifest themselves due to the inhibiting action of the Dominant White gene. Pigment is formed by melanocytes in feather germs, but there is a nontransfer of pigment by melanocytes to keratinoblasts.

Dominant White, Dun, and Smoky are alleles at the Dominant White locus. Dominant White and Dun inhibit the expression of black eumelanin. Analysis has revealed that Dominant White, Dun, and Smoky occur due to mutations of the PMEL17 (premelanosomal protein) gene. Dominant White, Dun, and Smoky are the only PMEL17 mutations that have been found to have a phenotypic effect in poultry.

The genetic sequence for Dominant White, Dun and Smoky are as follows:

“Sequence analysis showed that the Dominant White allele was exclusively associated with a 9-bp insertion in exon 10, leading to an insertion of three amino acids in the PMEL17 transmembrane region. Similarly, a deletion of five amino acids in the transmembrane region occurs in the protein encoded by Dun. The Smoky allele shared the 9-bp insertion in exon 10 with Dominant white, as expected from its origin, but also had a deletion of 12 nucleotides in exon 6, eliminating four amino acids from the mature protein.”

The Dominant White gene produces the following:

1. A white homozygote (I/I) which results in a white phenotype

2. A heterozygote (I/ I+) which results in a black-flecked phenotype

3. A homozygous recessive (I+/I+) which results in a black phenotype.

Modifying genes, which limit or expand the amount of black on a Dominant White heterozygote, affect the overall number of black feathers present on the plumage. The modifying genes also affect whether the black plumage feathers will be solid black and the white plumage feathers solid white.

The plumage color created from one copy of the Dominant White gene on Extended Black is currently approved in the Silkie breed with the American Bantam Association as the  “paint” color variety.

https://static1.squarespace.com/static/59ca6283f9a61eef0a37c335/t/5ac91e05f950b74252e4ac91/1523129865266/Bearded+Paint+Silkie+Standard.pdf

Some poultry fanciers may also be familiar with the currently unapproved breed historically known as “erminette,” whose plumage color is created from the a copy of the Dominant White gene on Extended Black.

F.B. Hutt completed a study on the Erminette breed and found that a typical Erminette is heterozygous for a gene and tentatively assigned the gene name as Er. When the birds in his study were mated together, solid white, black flecked phenotype, and solid black offspring were produced. He eluded to the gene being like dominant white in his study. Subsequent analysis has revealed that the gene which creates the plumage color for the Erminette breed is Dominant White (I). Additional information can be found here:

https://theamericanerminette.weebly.com/genetics.html

I purchased a copy of “The American Erminette” book that is available on the website above and found it to be very informative.

Some Ameraucana enthusiasts are also working with a project variety that results from a single copy of the Dominant White gene on Extended Black.

Bateson, W., 1902. Reports to the Evolution Committee of the Royal Society. London, Harrison, 160pp.

Hadley, 1913. Studies on the inheritance of poultry. I, The constitution of the White Leghorn breed. Rhode Island Agric. Exp. Sta., Bull. 155: 151-216. Plates I-IIL

Hurst, C . C , 1905. Reports to the Evolution Committee of the Royal Society. Report II. Experiments with poultry, pp. 131-154.

Kerje, S. The Dominant White, Dun and Smoky Color Variants in Chicken Are Associated With Insertion/Deletion Polymorphisms in the PMEL17 Gene Sequence, Genetics, Volume 168, Issue 3, 1 November 2004, Pages 1507–1518, https://doi.org/10.1534/genetics.104.027995

Kimball, E. On the Nature of White Plumage, Poultry Science, Volume 37, Issue 3, 1958, Pages 730-731, ISSN 0032-5791, https://doi.org/10.3382/ps.0370730. (https://www.sciencedirect.com/science/article/pii/S0032579119576374)

Lippincott, W. The Hereditary Relation of Dominant White and Blue in Chickens. Poultry Science, Volume 2, Issue 5, 1923, Pages 141-145, ISSN 0032-5791,
https://doi.org/10.3382/ps.0020141.
(https://www.sciencedirect.com/science/article/pii/S0032579119567670)

Sato, S. Mapping of the Recessive White Locus and Analysis of the Tyrosinase Gene in Chickens, Poultry Science, Volume 86, Issue 10, 2007, Pages 2126-2133, ISSN 0032-5791,
https://doi.org/10.1093/ps/86.10.2126.
(https://www.sciencedirect.com/science/article/pii/S0032579119392430)

Smith, L.T. On the Allelism of Blue Plumage and Dominant White, Poultry Science, Volume 48, Issue 1, 1969, Pages 346-347, ISSN 0032-5791, https://doi.org/10.3382/ps.0480346 (https://www.sciencedirect.com/science/article/pii/S0032579119528899)
« Last Edit: March 15, 2022, 10:28:23 AM by Lindsay Helton »
“If we live by the Spirit, let us also keep in step with the Spirit.” Galatians 5:25