crossing two barred breeds getting a surprize

[Henk69]

No, what I mean is that California grey should be B^sd = sexlinked dilution, another mutation at the Barring locus.

Are you 100% sure that he was B/B and not B^sd/b+ (or just B/b+)?

 

[centrarchid]

Quote:
The California grey roosters (n = 2) being are much lighter in overall coloration than dominique roosters. Former also has many solid white feathers. I believe them to to be pure and homozygous at locus of interest. I acquired the roosters in use from a group of about 40 individuals and they where fairly consistent in respect to overall appearance. They also breed true so that should exclude B^sd/b+ and B/b+. I assumed they were B/B like with dominiques. You are suggesting they are B^sd /B^sd which is a third allele possible at same locus?

EDIT FOLLOWS:

I read up on B^sd > B > b+ barring locus.

B^sd = almost self blue giving nearly white feathers when homozygous
B = typical barring in dominique and originally assumed for California grey
b+= non-barring wildtype

The roosters almost white which does not support homozygous for B^sd. Breeding true does support homozysity for some barring allele.


Some of possibilities on table:

Single barring locus
B^sd/B/b+ with b+ not an option since breeds true

or

Two barring loci resulting from past translocation producing two copies within genome, copy may or may not be on Z-chromosome. b+ probably not option for other this either
B^sd1/B1/b+1
and
B^sd2/B2/b+2

or

Other locus / loci not previously recognized that is modifying barring pattern

 

[Henk69]

So a pure B/B California grey is lighter than a pure B/B Dominique?

Is the pullet from the photo lighter than B/- Dominique? She should be B^sd/-, the cockerel B^sd/B.
Maybe literature exagerated the B^sd effect a little.

If there were a second barring locus than both barring mechanisms would probably show, like in the Zwalm valley fowl that shows both sexlinked barring and autosomal barring (campine). I mean these barrings are not aligned.
But a modifier would be a safe suggestion.

 

[centrarchid]

So a pure B/B California grey is lighter than a pure B/B Dominique?

Yes

Is the pullet from the photo lighter than B/- Dominique? Yes, very much so.

She should be B^sd/-, the cockerel B^sd/B.
Maybe literature exagerated the B^sd effect a little.

Very possible. or another loci modifies B^sd phenotype in California grey. Where in literature do you find California grey has B^sd?

If there were a second barring locus than both barring mechanisms would probably show, like in the Zwalm valley fowl that shows both sexlinked barring and autosomal barring (campine). I mean these barrings are not aligned.
But a modifier would be a safe suggestion.

Zwalm valley fowl looks very similar to California grey excepting latter lacks brown / red coloration. Both developed at roughly same time with same purpose in mind. California grey developed from initial cross of barred plymouth rock and leghorn. Barred plymouth rock with sex-linked barring but literature I does not indicate of leghorn used was bard. If so could have been of the autosomal type. Could also be that durng developement of California grey a copy of sex-linked loci coding for barring was inserted into an autosome. If so male California grey would be B/B sex-linked plus B/B autosomal and cross with female dominique B/- _/_ would yeild male B/B _/B and female -/B _/B (underscore means locus absent). Individuals with two B alleles (F1 female), regardless if at same locus or not would be difficult to distinguish from one that has three (F1 male).

Modifier most certainly possible.

 

[Henk69]

For what it is worth. I think it is unlikely/improbable.
In normal barring there is a dosage effect, so I would expect a gradual increase from 1 to 4 copies.

Leghorns were not autosomal barred.

This would be a good topic at the-coop.org

 

[centrarchid]

For what it is worth. I think it is unlikely/improbable.
In normal barring there is a dosage effect, so I would expect a gradual increase from 1 to 4 copies.

Dosage effect may be easy to detect at low copy levels but not at higher levels. My thinking that with increases in the number of copies producing a given product increases, in this case one that is likely regulatory, the increment of effects would decrease.

For example:
0 versus 1 copy - extremely large increase in gene product
1 versus 2 copies - double gene product
2 versus 3 copies - 50% increase in gene product
3 versus 4 copies - 33.3% increase in gene product

Difficulties of detection at high copy levels may be even more difficult in example since regulatory, dosage increases beyond a certain point may have no efffect if regulatory sites become saturated.

Leghorns were not autosomal barred. Is it not possible some lines were? Crossing over between chromosomes during development process for California grey certainly could have resulted in a an autosomal variant of locus coding for barring.

Another possibility certain to not exhuast all is that male B^sd / B not readily distinguishable from female B^sd/-.

This would be a good topic at the-coop.org. Probably so.

 

[Henk69]

That would not be crossing over but a translocation event. These events are mostly fatal.

 

[centrarchid]

Quote:
I was neglecting to distinguish crossover events between analogous chromotids and different chromosomes since in my manner of thinking distinction not all that important. Organisms I work with (fishes) do it so routinely and of such a magnitude that chromosome number and especially morphology not so fixed. When I talk about chromosome number, I have to say nominal number of chromosome types is 23 but 22 or 24 possible, sometimes within same population. Viability / fertility when animals of different chromosome numbers cross often quite high so long as complementary stretches of DNA can line up during meiosis.

 

[Henk69]

How good are you at Koi genetics?

 

[centrarchid]

Quote:
I am not a genetecist, at least not of the sort that deals with qualitative traits, so just knowledgeable enough to be dangerous. We have one of worlds largest goldfish and Koi producers, in respect to volume, about 1.5 h down road. One of my past students works there. It is becoming common knowledge to all that most of desired koi color patterns do not breed true and are very much a function of varigation (luck). Still can not get past pattern of starting with as many as possible and culling out 95% so that some balance will have desired appearance. A big part of rare high valued individuals is the individual doing the purchasing opinion.