jespah@milton.u.washington.edu (Kathleen Hunt) (02/04/91)
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.edun8243274@unicorn.cc.wwu.edu (steven l. odegard) (02/06/91)
Are there any modern textbooks detailing the coloration of guinea pigs? I am researching followups to the article in _Genetics_, vol 13 pp 508..531, "An 8-factor cross in the guinea pig". -- --SLO 8243274@wwu.edu uw-beaver!wwu.edu!8243274 n8243274@unicorn.wwu.edu
sbishop@desire.wright.edu (02/08/91)
In article <6130@ncsugn.ncsu.edu>, annw@ncsugn.ncsu.edu (Ann Williams) writes: > Kathleen, > > The books that I go by use the letters bb and not cc as chestnut. > The B meant black pointed horses and bb is non black pointed horses > which are the chesnuts. Also I use the Cr as the dilution gene. > So Bb or BB with the Cr would make buckshin and bb with the Cr is > palomino. The dominant A (red) is also needed to have the diution > gene expressed in the body coat or phenotype. I was grouping the bays > and buckshins together becaue of the B gene common to both and the > palominos and chestnuts together because of the lack of black points. > On the subject of the Bay stallion and Grey mare producing a chestnut. > For this to happen both parents had to be heterozygous. That is both > carried the recessive bb or as you say cc chestnut. Now correct me if > I am wrong but two heterozygous horses have a 25% chance of producing > the recessive color not 12.5%. Or am I missing something? I think what you are missing is the fact that the Grey allele is on a different locus. So even though the one parent is heterozygous Grey, the Grey gene can over ride the bb color if combined. The genotype of the grey parent can be Grey/chestnut, nogrey/chestnut, grey/bay, nogrey/bay. This is tenative since it is not certain that the grey parent carries bay also. This is possible since the mare has produced bay offspring. Only if it produces a bay offspring out of a chestnut stallion would it be proof that there is bay present. Otherwise, it COULD be just carrying chestnut. And it is possible that there is only one chestnut gene and nothing at all on the other part of the pair. So still another possibility is grey/nochestnut, nogrey/nochestnut. I hope I figured that all out right..... If anyone sees a flaw in this please let me know...
annw@ncsugn.ncsu.edu (Ann Williams) (02/09/91)
Sorry about the mix up. It was late at night when I was typing about Greys. I was wrong.