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From: jespah@milton.u.washington.edu (Kathleen Hunt)
Newsgroups: sci.bio
Subject: Confused about horse color...
Message-ID: <15746@milton.u.washington.edu>
Date: 4 Feb 91 08:31:59 GMT
Organization: University of Washington, Seattle
Lines: 53

Sue & Ann:
This is what I've figured out so far from your posts.

The color locus in question has three alleles: Bay (B), Chestnut (c), Pale (p).
B is dominant to c.  
p is a dilution allele, and is codominant to both B and c.
Okay.  So this is what you can get (considering only this locus):
	BB or Bc is bay -- brown body, black mane & tail..
	Bp is buckskin? (a "diluted" bay) -- tan body, black m&t, dorsal stripe.
	pc is palomino (a "diluted" chestnut) -- golden body, white m&t
	pp is cremora (is that like cremello?) -- whitish with blue eyes. 
	cc is chestnut -- reddish body, mane, and tail.
Is this right?  I am particularly unclear about the buckskin (see below).


Now back to Sarah's original question:

	Bay sire---Chestnut dam    Palomino sire---Chestnut dam
           B?    |     cc               pc       |      cc
                 |                               |
                Bay sire -----------------   Palomino dam 
                 Bc              |               pc 
                                 |
                              new foal

There are four possibilities (of equal probability, 25%):
B from the sire and p from the dam ==> Bp, buckskin (?) foal
B from the sire and c from the dam ==> Bc, bay foal
c from the sire and p from the dam ==> cp, palomino foal
c from the sire and c from the dam ==> cc, chestnut foal

Sue was lumping Bp and Bc together as "bay" but Ann seemed to be calling
one of them "bay" and the other "buckskin", or was Ann saying that what 
some people call "bay", others would call "buckskin"??  Well, as far as I'm
concerned, bay and buckskin are not the same color (buckskins have that nifty
black dorsal stripe!) and now I'm totally confused about what color Bp is.

Sue also described this cross:  Bay stallion (Bc gg) x Grey mare (?c Gg)
Grey is controlled by a different locus and has epistatic effects on the
bay/chestnut locus; Sue, will a G allele make the horse grey regardless of 
is at the bay/chestnut locus?  Did you have any way of knowing what the
grey mare's other allele was at the bay/chestnut locus?  
Sue got a chestnut foal:  cc gg
(therefore, one of the grey mare's alleles at the bay/chestnut locus was c.)
This was a 1 in 8 chance (50% chance of g allele from dam, and then 25%
chance of c alleles from both sire and dam; multiplies to 12.5% 
chance overall.)

Is this right?


Kathleen
jespah@milton.u.washington.edu