Topic Options
#117178 - 05/29/18 01:02 AM Egg Colour
Hen-Gen Offline
Ruler of the Roost

Registered: 10/01/05
Posts: 1163
Loc: Island of Fetlar, Shetland
I have heard it said that some of the genes that determine a dark brown eggshell colour are sex linked. Is this a fact or is it just one of those apocryphal tales?
_________________________
If you have nothing............
......... give it away!

Top
#117179 - 05/31/18 10:55 AM Re: Egg Colour [Re: Hen-Gen]
Wieslaw Offline
Moderator
Classroom Professor

Registered: 09/18/09
Posts: 3840
Loc: Denmark
I recall one article, where somebody suggested at least 12 pairs of genes affecting the brown egg shell color , but I do not recall any mentioning of them being sex-linked. This supposed sex-linkage you're writing about is especially common among Marans-people, and probably told to add more mystery to their breed. Another version I've heard: it's ONLY the COCK who pass the color.

Top
#117180 - 06/02/18 08:19 AM Re: Egg Colour [Re: Wieslaw]
Hen-Gen Offline
Ruler of the Roost

Registered: 10/01/05
Posts: 1163
Loc: Island of Fetlar, Shetland
Thank you Wieslaw. That's my experience too, a sort of implication with no supporting facts.
I considered a witty riposte to your observation about Marans people but knowing how easily humour can be misconstrued on multi-lingual sites I managed to restrain myself.
Your comment did make me laugh though!
_________________________
If you have nothing............
......... give it away!

Top
#117181 - 06/04/18 07:54 AM Re: Egg Colour [Re: Hen-Gen]
Redcap Offline
Ruler of the Roost

Registered: 08/14/06
Posts: 985
Loc: Germany
Probably the believe of sex linked genes has been developed due to the misinterpretation of the complex synergy of Epistasis, dominance, and additive effects of the egg shell genes.

http://www.the-coop.org/forums/ubbthreads.php?ubb=showflat&Number=114647#Post114647
_________________________

Top
#117184 - 06/05/18 05:29 AM Re: Egg Colour [Re: Redcap]
Hen-Gen Offline
Ruler of the Roost

Registered: 10/01/05
Posts: 1163
Loc: Island of Fetlar, Shetland
Thank you for the link, Robbie. One thing that mystified me was the statement '"this was an artificially made mutation, ie it did not occur naturally"
How so? Was radiation or a mutagenic chemical used?


Edited by Hen-Gen (06/05/18 05:31 AM)
_________________________
If you have nothing............
......... give it away!

Top
#117185 - 06/09/18 07:07 PM Re: Egg Colour [Re: Hen-Gen]
KazJaps Offline
Classroom Professor

Registered: 08/30/02
Posts: 2864
Loc: Australia
http://www.the-coop.org/forums/ubbthreads.php?ubb=showflat&Number=112691#Post112691
From D. Caveny 2002:
http://www.the-coop.org/forums/ubbthreads.php?ubb=showflat&Number=37936#Post37936
Quote:
Years back when we were making crosses between and among various strains and breeds we discovered two situations that seemed quite repeatable:

1. When white egg and brown egg birds were crossed it was extremely difficult to take tints out of the resulting "white egg lines"...we later learned that the brown pigments are controlled by multiple alleles some of which are sex-linked. One line was still throwing tints after 12 generations of selection.


2. When selecting for darkness of shells in brown egg crosses it is possible to select within populations for darker colors. It is most effective to select for those colors early in the laying cycle because eggs thend to lighten over the laying period. Intestinal microflora can also adversely affect pigmentation. The feeding of Virginiamycin (not approved then and maybe still not approved) would darken the pigmentation of the shells in brown egg breeds.


He doesn't mention what breeds/strains were crossed. He worked in the commercial poultry industry, but also kept autosexing breeds, etc. He has mentioned sex-linked correlations to egg colour multiple times (usually as a hint).

Plus there is the Z- chromosome sex-linked eggshell colour inhibitor pr.
http://www.the-coop.org/forums/ubbthreads.php?ubb=showflat&Number=111008#Post111008

*But pr also has deleterious traits, so not used in commercial white eggshell layers.


Edited by KazJaps (06/09/18 07:24 PM)
Edit Reason: Got rid of quote tags to make easier to read

Top
#117186 - 06/09/18 07:34 PM Re: Egg Colour [Re: KazJaps]
KazJaps Offline
Classroom Professor

Registered: 08/30/02
Posts: 2864
Loc: Australia
http://www.the-coop.org/forums/ubbthreads.php?ubb=showflat&Number=114i028#Post1140

-------------------------------

Previous post on pr research:
http://www.the-coop.org/forums/ubbthreads.php?ubb=showflat&Number=111008#Post111008

Found some answers in the following full paper:

The Effect of a Protoporphyrin Mutant on Some Economic Traits of the Chicken.
R. N. SHOFFNER, R. SHUMAN, J. S. OTIS, J. J. BITGOOD, V. GARWOOD and P. LOWE
Poult. Sci. May 1982 vol. 61 no. 5 817-820
Abstract

How pr came about...
Quote:
A mutation which drastically reduces egg shell protoporphyrin pigment is closely associated with a translocation, t(Zq+;lq-), between chromosome # 1 and the Z sex chromosome.
This translocation was induced by x-ray irradiation of semen from a Cornish male and subsequent insemination into White Leghorn females (Zartman, 1973).

This stock was kindly furnished to the Minnesota Cytogenetics Laboratory and in ensuing outcrosses to the Regional control Rhode Island Reds (RRc) there was a striking segregation for egg shell pigmentation among the sibling daughters from heterozygous translocation males.

The white shell trait is inherited as a sex-linked recessive and is intimately associated with the break reunion point of the translocated chromosome (Shoffner, 1978).

The symbol pr is used to designate the phenotypic expression, i.e., lack of protoporphyrin pigment on the shell.


Looks like pr and S loci may have been close on the Z chromosome...
Quote:
Homozygous translocation (TT) males were outcrossed to normal (NN) females with silver (S) locus serving as a marker to aid in detecting possible crossover progeny. The locus for silver is on the same (q) arm as the translocated segment of the # 1 chromosome (Bitgood et al, 1980).

Unfortunately due to using white Leghorns (with I) as their source of S, they couldn't make accurate linkage scores between pr & S.

But the following....
Quote:
Crossover progeny with mutant white eggs and a standard chromosome complement were not recovered. However, two individuals were identified with a recombination between the silver locus and the translocation break point.

So it looks like there was a close linkage between pr & S loci.

But there was the problem of consequences on how pr came about - ie artificial chromosome translocation, not a single gene mutation.
Quote:
While the mutation has these attractive manipulative features, there are complications as the mutation appears to be intimately associated with the translocation which produces semi-sterility in the heterozygous males and the hemizygous females. In order to bypass this complication, a recombination introducing the pr locus into a standard chromosome would need to be recovered in crossover progeny.

And as was mentioned in the previous quote, the pr gene didn't segregate out without the rest of the translocation.

Top
#117187 - 06/10/18 12:49 AM Re: Egg Colour [Re: KazJaps]
Hen-Gen Offline
Ruler of the Roost

Registered: 10/01/05
Posts: 1163
Loc: Island of Fetlar, Shetland
Excellent information. Thank you KazJaps.
_________________________
If you have nothing............
......... give it away!

Top


Moderator:  Admin @ The Coop, Henk69 
Who's Online
0 registered (), 78 Guests and 0 Spiders online.
Key: Admin, Global Mod, Mod
Shout Box