[Jacob-list] Freckles and Ticking outside the showring
Jacobflock at aol.com
Jacobflock at aol.com
Thu Apr 27 01:50:40 EDT 2006
These two genes seem to be in Jacobs and the evidence seems to support a
"piebald gene" hiccup. Spinners probably know more about freckles and ticking
than many show judges.
The Jacob dominant black and recessive piebald begin to work in embryo,
immediately . The results of these color genes show up and are visiible at about
one month. The Jacob's dominant black comes from the melanocytes formed in the
embryonic skin cells. The cause is the protein tyrosine which produces the
black ... eventually hair, wool, hooves, horns, nose, knees, etc.; a copper
based protein. The recessive white pieblad spotting (ss) (as opposed to dominant
Spotting (SS)) is operating in conjunction with the tyrosine protein and
"shuts off" the eumelanin producing melanocytes. The piebald gene messenger
"says" to the dominant black, "you can't go there". If the "piebald" gene is loud
enough and "super" strong, the result is a 80% white offspring; strong a
perfect 60-40 or 40-60 etc., weak piebald produces a 20% white. An so it goes as
the cells grow from embryo to fetus.
Two genetic "mistakes" have been observed. First, a piebald gene that skips
spots and produces "Freckles" (a piebald painting error ... like skipping a
spot of black) and these freckles are often observable at birth. Freckling
(production of black fiber from black skin) seems to be dominant to non-freckling.
Some freckling is the production of a black skin spot (often with white
fiber) which is the result of the sun's rays exciting melanin in the skin (we
'melanin' tan from the sun). Second, "Ticking" which is not visible at birth but
appears as a growing number of black spots with black fiber that increase in
number and size as the Jacob ages ... it may even appear to turn almost
completely black with aging. Ticking also seems to be dominant to non-ticking.
Thus, to conserve a consistent piebald gene, one might watch both parent and
offspring and note the expression of freckles and ticking so that the gene
pool will not get overloaded by these genes just as we avoid the extremes of the
very "oversctive" or "underactive" piebald gene or even avoid the misplaced
Jacob piebald pattern gene in breeding efforts.
There are a number of articles available on these genes and a starting point
might be COGNOSAG (Committee on Genetic Nomenclature on sheep and goats).
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