[Jacob-list] Jacob lilac question

[Jacobflock at aol.com]

In a message dated 8/6/01 10:18:34 PM Central Daylight Time, 
WenlochFrm at aol.com writes:

<< I'm trying very hard to understand what Neal and Fred have said. Fred, 
isn't 
 Sponenberg saying the opposite of what you are saying? "Lilac is 'not 
 black'." Doesn't he mean it is not eumelanin? And, is it possible lilac is a 
 dilute? ...but on asking Sponenberg that question over a year ago, he said 
it was highly unlikely knowing what he knew about sheep color genetics. ... 
how 
 can you, Fred, be so sure that it isn't possible to have pheomelanin in the 
 Jacob lilac? One reason I ask is because last year I saw a lilac ewe that 
was 
 red with a brownish cast....  Have any lilacs been tested for pheomelanin to 
rule it out? 

 Joan Franklin
  >>

I am also trying to understand.  I thought that my email regarding the Jacob 
lilac was sufficiently equivovcal (a vacuum of certitude) that I can chase 
another's ideas.  

Based on the various emails, here is perhaps a better POSSIBILITY .... I'll 
commit the E (color intensity) and D (dilution) possibilities to the 'tabula 
rasa'... and pick up on some variations from Neil's post and Ingrid Painter's 
book section on Jacob color genetics and lilacs and include observations from 
various posts which seem to support the conclusion that a LILAC IS RECESSIVE.

If the E (extension locus, ED which extends COLOR in a solid color, affects 
intensity and blocks the A agouti pattern and as E+ which allows an A 
expression as a recessive) HOW MIGHT the A locus play a roll?  Here there 
PROBABLY can be a series of alleles; A*white dominant to A*gray, A*white and 
A*grey both being dominant to the white belly Mouflon type (A*whitebelly), 
and A*whitebelly being dominant to A*blackbelly or self colored.  

SUPPOSE then A*white over-rides or is epistatatic to a Jacob black locus, B 
(black locus). Black (B) is KNOWN to be DOMINANT to b (brown).  The B (black) 
should be homozygous in a "pure" Jacob .. "pure" suggesting homozygosity by 
trait vs. by breed in this case.  Thus the 'Black color' of the Jacob must be 
expressed in the absence of A*white controlled by the piebald ss. 

Black and white Jacobs (with the ss piebald) in this theory would be: (1) 
A*whiitebelly/A*whitebelly and B/B black Or (2) maybe a 
A*whitebelly/A*whitebelly and Bb, i.e, black/brown.  Remember you see black 
if B is dominant to b, OR A*white and BB or Bb.

A "lilac" might be a Gray (Black to gray to blue) might be (1) A*grey/A*grey 
and BB or (2) A*grey/A*grey and Bb (dominant black), and (3) 
A*grey/A*selfcolor with BB and (4)  A*grey/A*selfcolor and Bb.

A gray (black to brown to tan) MIGHT be (1) A*grey/A*grey and bb;  Black is 
always dominant to brown.  So if one has a brown bb (this is the fiber root 
color), it is not a "pure" black OR (2) A*gray and Bbs. (Half being brown to 
tan).

Then, as have been observed, there is the question of "light" lilac and 
"darker" lilac.  Here the question of separating environment from the E locus 
of trait expression must be examined.... this is the UV activitiy on fiber 
and even mineral content (copper) may come into play.

The ss recessive piebald puts down its A*white over the BB black or Bb in 
both breed specific markings and/or random markings.  What would have to be 
accounted for is the interaction of A*white and the ss gene; does it have 
multiples alleles for body and extremeties(?) that could explain why there 
are no Black belly Jacobs, black leg Jacobs and the absence of color in the 
ss area (A*white in black and whites). What proportion of progeny from a 
homozygous or heterozygous Jacob lilac have black leg markings?  

The prematuring gray certainly appears DOMINANT.   The prematuring gray might 
then overide the E (dominant to Black) which would allow the expression of 
the A*grey which would be a homozygous expression OR is it a  compromised 
Black or gray, perhaps even a "busted" tyrosinase pigment converter gene.   

I don't have any credentials to suggest that I am a color genetics expert and 
like most, ask the question "why"?  I don't know what Phil said with respect 
to black and lilac color;  it was a question relating to the content and 
context.  If the Jacob is a dominant B Black, I THINK one ought to seek 
explanations within the breed; a dominant black.  There are also questions as 
to what would compromise Black and how comfortable one feels about the 
genotype, homozygous or heterozygos.  I am convinced that the starting place 
must be a known Jacob (black vs. red) with several generations of progeny; 
look to the breed origins (e.g., Werner, Ryder and Alderson ... black vs. red 
) rather than a recent fence jumper. 

This weekend we saw a "jacob" flock, one registered Jacob among about a dozen 
black and white sheep. Most of the flock came from Witchita Falls.  About 
four of the jacob ewe lambs were polled, scurred and wooly all over.  I did 
not conclude, nor would anyone, that since the four jacobs had no horns and 
were wooly allover that Jacobs are polled, scurred and wooly all over or that 
these are "pure" Jacobs.  As I recall... and this is awaiting pictures (from 
the drugstore chain being purchased by Jacob breeders)  all the COLOR was in 
the right places.

Fred