[Jacob-list] my suspicion

[Jacobflock at aol.com]

In a message dated 7/12/2008  5:17:03 PM Central Daylight Time, 
lambfarm at sover.net writes:




Interesting, Fred.  The guy who has one or two a year  has only jacobs on his 
place.  The person he got the ram from many years  ago, had many years before 
that, a few romneys on her place, but says her  jacobs are purebred, and I 
tend to believe her.  They all came from a  flock some nuns had in Maryland many 
years ago.  She's changed ram lines  very seldom, breeding pairs, father to 
daughter, father to granddaughter,  cousin to great granddaughter, father to 
great great granddaughter, and it is  in this generation and beyond that these 
white ones appear.  A friend has  one of them which was wethered, a male.  I 
will check it out, see if  there is any black skin, and take photos. I am 
tempted to believe that  somewhere along the line there was a horned dorset and some 
characteristics  got buried deep, in both male and female or father and great 
granddaughter,  and the genetic slot machine came up with the right combo to 
produce the white  lamb.  But hey, I know very little about such things.  I 
have no  idea if any white to white have been bred. I think maybe a neighbor of 
his who  got a white ewe and white male may have bred them. I'll ask and see 
what the  result was...



----- Original Message ----- 
From: _Jacobflock at aol.com_ (mailto:Jacobflock at aol.com)  
To: _lambfarm at sover.net_ (mailto:lambfarm at sover.net)  
Sent:  Saturday, July 12, 2008 5:22 PM
Subject: Re: [Jacob-list] my  suspicion


In a message dated 7/11/2008 5:08:51 AM Central  Daylight Time, 
_lambfarm at sover.net_ (mailto:lambfarm at sover.net)   writes:


someone said that they had a white lamb: where does that come  from; I said I 
had seen white lambs in two flocks, both of whom did pretty  intense line 
breeding, and wondered what the relationship was, figuring it  just upped the 
possibilities of bringing out a possible recessive gene for  one big 
spot...Someone also called the white lamb albino, but it was blue  eyed, and I wondered, 
because my impression was that a true "albino"  animal has red eyes, if this 
was NOT an albino, but just a white  lamb.  Also, the white lambs I'd seen had 
white hooves and white  horns.




----- Original Message ----- 
From: _Jacobflock at aol.com_ (mailto:Jacobflock at aol.com)  
To:  _patchworkfibers at alltel.net_ (mailto:patchworkfibers at alltel.net)   ; 
_lambfarm at sover.net_ (mailto:lambfarm at sover.net)  ; _jacob-list at jacobsheep.com_ 
(mailto:jacob-list at jacobsheep.com)   
Sent: Thursday, July 10, 2008 11:01 PM
Subject: Re:  [Jacob-list] my suspicion


Where does this string start ...  like I read half an e-mail.  Is the 
question about the difference  between S and s (dominant and recessive spotting)? or 
a recessive that  has whitened one side and not the toher?  I'm a couple ogf 
cards  short of a full deck.

Fred Horak 
St. Jude's Farm
1165 E.  Lucas Road
Lucas, TX   75002






I tried responding to  this and ended up deleting a whole bunch of stuff 
becasuse I can't hit the  right keys or control the mouse.  Here comes another try 
at a "White  Paper".

If one begins with the genotype of the Jacob as a dominant  black, piebald 
and accepts the recessive character of the piebald (the small  s of the dominant 
big S Spotting gene), then one should not expect an all  white "Jacob".  No 
amount of recessive spotting in the dominant Black,  by definition, can give a 
dominant S, all white sheep, and a Jacob cannot be  an S (it is an oxymoron).  

Soay sheep (apprarently non-piebald)  have been bred to Jacobs and produced 
piebald crosses indicating that  piebalds breed true for the piebald gene even 
across breeds (ABRO flock on  St. Kilda).

However, and "over active recessive spotting gene" can  result in more white 
(say 95%) but even at the extreme, the piebald or over  active spotting ghene 
does not mask black eye markings or the nape of the  neck (see some old JSC 
Journal articles from 1996, 99 and 2002 with  references to Partridge and the 
pictures and descriptions of 5 levels of  piebald markings.

Ryder and Adalsteinsson explain (ARK  345-347,  reprinted JSC 12/98) how the 
s (recessive piebald) gene prevents the  black color cells from forming qnd 
how the finer white wool replaces  it.  They also describe the major color 
geneotypes.... Chromososomal  locus A has a series of alleles: White (A1) is 
dominant to grey(A2) and both  white and grey are dominant to wild or mouflon (A4) 
(white belly) and all  are dominantr to 'wild color (A5).  The locus A 
overrides (is  epistatic) to B Black ... and Black is dominant to brown.  At the end  
of the paradigm, there are two genotypes fro black and nine for white (A1,A3  
and A5) and, of course, the recessive spotting gene.  A lot of color  gets 
hidden by white.  R and A did a series of test breedings to verify  these 
genotypes and they still seem to hold true.  They do point out  that "positive 
selective breeding" can lead to a dimunition of color  traits.

The story of the "pure white Jacob" has been told several  times before and I 
think I recall a story that Ed Bissell had "one" that  Sponenberg thought 
might have a "one spot piebald" ... which would be a  tongue in cheek "S" since 
the s piebald creates a spot.  The dominant S  white should be a white sheep 
... keratin fibers being white ... the absence  of activated cellular eumelanin 
(black) ... more blue eyes in the population  ... white feet .... white horn.  
If albino, the eyes are pink or  redish.  

If there is any black around the eye or on the nape,  it is an over active 
piebald ... you can't hide piebald.  Are there any  black fibers or black skin?  
But that is not to say one can find the  gene that initiates the production 
of eumelanin for the dominant Black but a  specific gene can get "goofed up" 
even at the dermis or follicle production  level.

When one produces and all white lamb one might look for black  skin ... any 
black fiber.  Note the observations, parents... and try to  duplicate it, and 
parentage.  Also breed the "white Jacob" to a Jacob  to see if the evidence of 
the recessive gene shows up in the  offspring.  Few people breed culls, why?

Perhaps the lambs are  from registered parents (a requirement that they be 
marked to meet a breed  standard) ... has it happened before or are all 
offspring from the parentage  registered or are offspring selected to be registered.  
This later  situation often blurring the principle that a breed consistently 
reproduces  its type.  The apparent looks masking the real genotype.

I  hope this contributes something to understanding.  My bias is against  
white Jacobs but that does not stop me from trying to understand why they  arise 
from time to time.  I just haven't personnaly seen a white  Jacob in person 
(although I've seen a number of hornless Jacobs) and I  have not heard of anyone 
following up on the issue.

Fred  Horak
St. Jude's Farm
1165 E. Lucas Road
Lucas, TX  75002





Has anyone else seen one  of these "white Jacobs"? 



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