Extended Black
Extended black, allele symbol E, is the most dominant of the e-locus alleles.
Contents
Degree of dominance
There is some discussion about how a heterozygous E/? chicken would differ from a homozygous one. Complicating factor is whether additional melanizers are needed to achieve a true solid black chicken. In crossings these melanizers become partly heterozygous like the e-locus.
Phenotypic effect
There is some discussion about how a homozygous E/E chicken would look. In one view E/E without additional genes always gives a full black chicken, both genders. In other animal species that is indeed the rule. The below is another view, the current consensus.
chick down
Typically penguin black chick down.
rooster
A black enhanced form of the black breasted (wildtype) phenotype, with one significant difference: the wing triangle is black instead of groundcolored (pheomelanin). This is called "crow wing". To get a solid black rooster, additional melanizers are needed to cover the groundcolor leaking areas. Very similar to a coarse birchen rooster without any breast lacing.
hen
May be almost solid black. Complicating fact is that the melanizers that theoretically complete the solid black phenotype may be more effective on females. So the E/E female without additional genes may be similar to the birchen female: more or less groundcolored hackle. Breast lacing probably absent.
Heterozygosity
- Extended black is completely dominant to wheaten .
- Extended black and birchen are very similar, so heterozygotes probably not obvious. Breast lacing probably absent.
- e+/e^b: see remarks above.
Epistatics
Extended black is epistatic to (covers) columbian.
When diluted to blue, the phenotype can be affected by pattern genes like Pg and/or Ml to render a black lacing. Other patterns like multiple lacing or spangling can not be achieved.
Effects of Db on extended black are not well documented. Most effective on males.
