Chicken Genetics

[snowbird]

Welcome Henk,

Very interesting stuff.

Since the DUtch are among the best horse breeders and flower breeders in the world, I suspect chickens and cattle are up there too.

I learned my horse breeding criteria from the Dutch. THe data is collected by trained personnel and the 26 traits are put into a data base. For those who are new to all this the traits are the expression of a number of genes acting together. Length of neck, length of back, angle of hip.

It is all about selection.

Arielle, Read Henk69 post about the Genetics, let me know how this relates to the talking we have been doing in relation to the Large Fowl Marans, better still read about three times and PM me with what you get from the post.

 

[3riverschick]

Welcome Henk,

Very interesting stuff.

Since the DUtch are among the best horse breeders and flower breeders in the world, I suspect chickens and cattle are up there too.

I learned my horse breeding criteria from the Dutch. THe data is collected by trained personnel and the 26 traits are put into a data base. For those who are new to all this the traits are the expression of a number of genes acting together. Length of neck, length of back, angle of hip.

It is all about selection.

===============================
How very true. We bred rough and smooth collies from 1995 -2009. Working, service and show all rolled into one. To do it we crossed 3 vintage linebred lines, each unrelated to one another for at least 4 generations. I used all kinds of breeding plan info from multiple species like canine, poultry and racehorse. I found much wisdom in Mitchells' Racehorse Theories book and the writings of the Aga Khan. esp the Aga Khans' wisdom on selecting balance in the abstract. Even used Percentage of Line Inheritance trial pedigrees looking for poetic symmetry in the abstract(not practical facts). The point is, so much research is involved in solving the mysteries of breed type. Then the selection still has to follow.
The books on Solving the Mysteries of Breed Type for dogs and Davie's " The Theory and Practice of Breeding To Type"(1891) were also helpful.
Then I moved to poultry and what a different world! So many sex-linked genes and swapping the XX and XY genes. I agree, it is tougher than breeding dogs. The principals of selection and balance in the abstract remain the same. Balance and Symmetry, any great animal is more than the sum of its parts. The great APA judge and breeder W.H. Card wrote in his book how to achieve it. http://archive.org/details/cu31924003158312 Judge Card was Dan Honour's Uncle's Uncle. The apple surely didn't fall far from the tree there.
Well at any rate, symmetry still reigns supreme and selection still survives as the best way to achieve it.
Best Regards,
Karen in western PA

 

[tadkerson]

Knowing about genes being recessive and dominant and the rest of genetic stuff is very good but genetics is far more complicated than Mendelian genetics.

For example:

Skeletal variability in dogs is due to tandem repeats ( pieces if DNA that repeat themselves) located within the coding region of two developmental genes. This is one reason why you can get dogs with such variation in size and shape. Basically the developmental genes are different in different breeds because the tandem repeats make them different.

Research has also found that the tandem repeats can be found in promoter regions of genes. This would explain why there can be such variability in dogs and chickens. The promoter region of a gene controls how a gene is expressed, think of it being like a switch turning on and off a gene.

My point is that its not always genes that make a difference. There are many different mechanisms that are used by organisms to express color etc. Genes are very important but there are other factors that can alter the expression of a gene. So it may boil down to the gene plus some other mechanism that is causing the difference in expression.

One example of this is found at the henny feathered gene. Henny feathered males and non henny feathered males have the same henny feathered gene. The genes or coding regions are just alike. The difference between the two is the promoter region. Normal males have a promoter region that keeps the gene turned off while in henny feathered males there is a retro virus insertion in the promoter region that turns the gene on. So there is a change in the promoter region that is causing the difference not the gene.

It is things like this that can make the differences in animal genetics.

Tim

 

[ThiefPouter06]

What I find interesting about chicken color genetics is that when crossing two differant colors you seem to always have some degree of both colors in the F1 regardless of dominance. For example black(dominant) to a BBR(recessive) creates black but they will have red feathers in the hackle. Fun stuff

 

[Arielle]

Tim, thanks for your input.

I'm certain as we now have the ability to chemically decode all the genes, gene interaction if far more complex than we ever dreamed it was. CLearly Mendal was a revolutionayr thinker of his time. THose principles still apply,that gene codes are acquired from parents. THough in plants we have the ability to chemically add genes in the labs. Genes are turned on, turned off, etc. Genetics are very complex.

I didn't go into the environmental factors that effect gene expression. Most genes have low heritabilty values, meaning the "environment" also has a huge effect on the expression of the gene.

The intial post was started because I kept reading bird genetics are different than mammals as if selection and gene inheritance was somehow unique and that some how inbreeding cannot occur in birds.

In selecting buckeyes for the breeding pen, skilled hands can feel the difference in breast thickness; in sheep we use our hands to feel the thickness of the leg muscling. A subjective method, but a good selection method none the less for increasing muscling.

If I want healthy chickens, I cull the sick, and do not breed on those genetics. In horses, we can scope for roaring, in the Dutch those stallions are not used for breeding. BOth conditions are known to be heritable. I don't need to know the specific genes to breed healthy birds or horses, just that the condition has a genetic basis.

I do expect birds, reptiles, mammals, insects, etc to carry different genes as they separated on the tree of life long ago. My point was and is that the selection of genes morphs the creature. I haven't heard anything yet that says otherwise.

Keep the details coming--much to learn about chicken genes!!

 

[Henk69]

What I find interesting about chicken color genetics is that when crossing two differant colors you seem to always have some degree of both colors in the F1 regardless of dominance. For example black(dominant) to a BBR(recessive) creates black but they will have red feathers in the hackle. Fun stuff

That is a common misconception.
What you see is the effect of the dominant extended black mutation without the aid of the extra melanizers that you need to get a solid black rooster.
The BBR does not have them.

 

[Arielle]

What is BBR?



In black copper marans there are heavy discussions about the hens being over melanized. Which really means that BCM SHOULD lack the extra melanizers for the hens to have the red leackage in the neck hackles.

Did I understand this correctly?

How is the rooster color , especially the hackles, effected by overmelanizations compared to correct, (fewer) melanizinng genes?

 

[gallorojo]

BBR- Black Breasted Red

 

[Arielle]

THank you.

 

[ThiefPouter06]

That is a common misconception.
What you see is the effect of the dominant extended black mutation without the aid of the extra melanizers that you need to get a solid black rooster.
The BBR does not have them.

So to get a black chicken there are more than one gene needed? wow now its even more interesting.