black,
wild red, red, dun dilution, agouti, brindle, roan
Unfortunately, most registries
were started by “laymen” who assign "color classes"
by phenotypical observation and not genotype. Not to single out, but
let’s just use the American Galloway Breeders Association (AGBA)
as an example. The AGBA registers three solid colors; Black, Red and
Dun. DEFINING Coat Color: Solid coat color in cattle results from the presence or absence of melanin in hair coat.
(MC1r): The Melanocyte Stimulating Hormone Receptor Gene (MSHr), also called the Melanocortin Receptor 1 gene (MC1r) is the source of black or red color. EXTENSION: The E stands for Extension. Solid Black, Red and Wild-type red cattle are the result of Extension (E) locus (listed in order of dominance):
BLACK:
The black allele is abbreviated (ED). RED:
The red allele is abbreviated (e). WILDTYPE:
The wild-type allele is abbreviated (E+). Wildtype alleles produce both eumelanin and phaeomelanin through intermediate amounts of tyrosinase. The ratio and distribution of these two pigments may be modified by other genes. The visible expression of eumelanin seems sex linked. This can be observed in wild-type (E+) bulls, which express a darker head, neck and feet as compared to females. Heterozygous (E+/ED) are most often dark black in color, since even one copy of ED will produce an over-abundance of eumelanin. In heterozygous (E+/ee) variability of coloring in these animals is expected, and poorly documented. AGOUTI:
E+ can be further modified by the Agouti (A) locus. Agouti comes in
several forms and has distinct effects depending upon combination. It
is not well understood or documented across breeds. The existence of
a recessive black Agouti allele (a) has been postulated with some supportive
documentation, having the effect of modifying Wild-type E+ black/red
to black. Thus, not all phenotypical “black” animals may
be black (ED/ED). Tracy Wood's red roan Galloway cow, New Zealand
another rare animal;
A single dose results in expression (dark points) and a double dose results in amplified expression (light points). Heterorzygous White Galloways are (Cs29/cs29). Homozygous White Galloways are (Cs29/Cs29). Non-White Galloways are (cs29/cs29). Thus, a heterozygous Cs29/cs29 can produce non-white offspring when mated to Cs29/cs29 or cs29/cs29.
2 heterozygous Cs29 White Galloways will produce some solid colored calves;
There is nothing mysterious about White Galloway pattern. Autosomal incompletely dominant White x White breedings, where both parents are heterozygous for White, can produce a 1:2:1 ratio of Homozygous White : Heterozygous White : Black (non-white) offspring. This only applies to the "overall color being white w/points (light or dark)" or solid colored... H5 Spotty, an “overmarked” White Galloway bull RIGGIT: “Riggit is a true (phenotype) trait. Riggit expresses from a combination of two or more genes in co-expression that produce a unique and somewhat variable, multi-factoral phenotype. In some breeds a "static" pattern is likely produced by a single primary gene (or linked gene complex) with minor variance, i.e. Gloucester Lineback, Lynch Lineback, Pinzgauer, etc... Costa vom Felde
We have long known that both wild-type black (E+/E+) and wild-type red
(E+/e) cattle exist in Galloway Populations. We now know the brindle trait exists in wild-type (ED/E+ Abr, E+/ E+ Abr)
Galloway populations, thus showing that wild-type can be further modified by pattern and spotting traits. 4 seite 15 unten_galloway kalb farbschlag dun ~ Galloway-Kalb, Farbschlag dun, oefm.de Golden dun results from heterozygous codon deletion within the PMEL
gene (p.Leu18del) PMEL +/del. While Dun may present in spotted (white park) and patterned (Riggit / color-sided / Lineback / Witrick) & (brindle) Galloways, the locus is only a mutation of solid color, i.e. black or red. The presence of spotting or pattern traits has no effect on the expression of Dun. Thus, there are two common “Dun” phenotypes: Dun Black and Dun Red. Dun modifies black or red, and should be stated first in name or genomic descriptor. With autosomal mutations of color across species, such as Agouti and Dun, both recessive and incompletely dominant, variation of color (shading) is to be expected. This as a result of “autosomal concentration”, .i.e. a sort of cumulative effect. Just as an autosomal incompletely dominant trait has distinct impact in both heterozygous and homozygous fashion, so does an autosomal recessive trait. Only in the latter it takes much observation to take note of the subtle differences presented in the heterozygous form of a recessive. Thus, all light-colored animals are not the result of Dilution genes. Dun is dominant to black. The effect on red is more uniform. Homozygous red (e/e) animals that are also heterozygous at the Dun locus will be duns. Animals that are homozygous Dun show a more extensive reduction in pigmentation in both black (ED/ED) and red (e/e) coloration. A homozygous black Galloway (ED/ED), but also homozygous for Dun, will appear silver. On the other hand, individuals homozygous for Dun and also homozygous red (e/e) would look very light red or even yellow. Animals heterozygous or homozygous for Dun and (E+/E+) or (E+/e) will be darker than (e/e). The actual shading will vary depending upon specific combinations (zygosity). CHOCOLATE DUN: Is likely the result of combination of Dun with various types of E and A alleles in co-expression. ADDITIONAL NOTES: As hair grows during
embryonic development, melanocytes develop and migrate to the follicles
to produce pigment. Further traits can modify color coat in utero, shortly
after birth or with aging. Additional traits can modify for spotting
or pattern. This informal article is
generously provided by Alan S. Bias, and is the result of discussions
mostly in 2018 About the Author: Alan S Bias is an independent researcher active in evolutionary biology as a member of Independent Academia, and has published many papers that document his research findings. In this article, he shares some of his knowlege about the genetics of the most common dilution in beef cattle. Alan is a rare Shetland Sheep, Galloway Cattle and Domestic Guppy breeder & exhibitor of 47 years. For the last 35 years he has specialized in strains known to breeders as "Swordtail Guppies". For nearly 20 years he has done cellular level research, combining formulated breeding tests & systematic observation to help breeders understand the complexities of modern Guppy genetics in the strain being produced. Alan lives in Lewisburg, West Virginia, United States. alansbias@aol.com |
https://commons.wikimedia.org/wiki/File:Farbschl%C3%A4gePigmentierungenGALLOWAYS.jpg
click to open large blue roan chart in separate
window
vintage Highland painting - from Sheila Schmutz genetics page
» see also » Genetics of Coat Color (CC) in Cattle page 1 ~ the Basics of Bovine MC1R Black & Red » Ongoing Research on: the White Park Pattern |
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