Also gorgeous.
Learning Genetics?
- Thread starter myawesomepullets
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- chicken genes genetics
I just noticed this thread, but I see it's already grown quite long.
I'll try not to repeat too much that's already been said
Information:
Male chickens have ZZ sex chromosomes, females have ZW
(If you are used to mammals, that makes chickens seem backwards.)
The Z chromosome has several genes that are the basis for the common "sexlink" chickens (males & females look different from the time they hatch.)
The female determines the gender of the offspring, because she gives each one either Z or W.
Sources I have found useful:
http://kippenjungle.nl/sellers/page3.html
(has a list of genes, with their symbols and a little bit about them)
http://kippenjungle.nl/sellers/page2.html
(more information about some specific genes)
http://kippenjungle.nl/breeds/crossbreeds.html
Chicken genetics calculator (There are many slightly-different versions.)
The default has all the genes set to wild-type (what the junglefowl have, marked with +)
You can change any gene in the dropdown boxes, and the little picture of the chicken will change.
It can also calculate what offspring will come from each mating, but I mostly use it to help understand what genes do what.
Yes, the pictures are rather cartoon-ish, but they are good enough to show some things about how the genes behave. For example, if a gene affects just the black on the chicken (Blue does this) or if the gene affects both the gold and the black on the chicken (lavender does this), or if it changes where the gold and the black are located on the chicken (e-locus, Pattern gene, and Columbian are examples of this)
Extended Black is at the e-locus. There are lots of alleles at that locus. All of them affect how the black & gold are distributed on the chicken. Extended Black is the most dominant of them, and "extends" the black to cover the entire chicken. A chicken with Extended Black can have bits of other colors leaking through, but is at least mostly black. Carefully bred black chickens will have some other genes that help make them black all over. A Black Sexlink hen would be an example of Extended Black without the other modifiers (she usually has some red on her chest.)
recessive white is recessive, obviously. A chicken with two copies of the gene (homozygous) will have pure white feathers, no matter what other color genes it also has.
Dominant White changes black to white. It affects all black on the chicken. So an all-black chicken becomes all-white, but a gold chicken with black lacing becomes a gold chicken with white lacing (examples: Buff Laced Polish, White Laced Red Cornish). To get a nice clean white often requires the chicken be homozygous for Dominant White. If it is heterozygous for Dominant White, it will tend to have some black leakage. You can see this leakage in photos of California White chickens, and especially in Paint chickens.
The e-locus affects how the colors are distributed on the chicken.
I suggest you go to the calculator and play around with changing just the e-locus (top gene in the list), and see the effects. All the females are different, although some of the male forms look alike.
Other genes can also affect how the black & gold are distributed on the chicken (examples: Pattern gene and Columbian)
Silver is a dominant gene that turns gold into white. It is on the Z sex chromosome, so males can be homozygous or heterozygous, while females can only be hemizygous. Heterozygous males tend to look a bit yellow, instead of being a nice clean white.
Better examples would be Light Brahma, Light Sussex, Columbian Rock, Columbian Wyandotte.
Buff Columbian also exists (example: Buff Brahma, Buff Columbian Wyandotte)
And Red Columbian with Dominant White gives Gold Comets and ISA Browns (plus a multitude of look-alikes with various names.)
It is not true for any other genes.
Yes, but there is a detail your list doesn't mention.
Homozygous pea comb makes the comb & wattles smaller. Heterozygous pea comb does not do that. Any breed that is pure for pea comb will have a small comb and small or apparently-missing wattles. Examples: Brahma, Dark Cornish, Sumatra. Crossing them with other breeds produces hybrids with larger, odd-looking combs, and normal-sized wattles.
r+/r+/P/P will have a small comb and small wattles
r+/r+/P/p+ will have a larger comb and normal-sized wattles
This also applies to Walnut combs-- the ones homozyous for pea comb will have much reduced wattles and small combs as well. Example: Chantecler, Yokohama.
R/R/P/P is expected to have small comb and small wattles
R/r+P/p+ is expected to have larger comb and normal-sized wattles
I'll try not to repeat too much that's already been said
Information:
Male chickens have ZZ sex chromosomes, females have ZW
(If you are used to mammals, that makes chickens seem backwards.)
The Z chromosome has several genes that are the basis for the common "sexlink" chickens (males & females look different from the time they hatch.)
The female determines the gender of the offspring, because she gives each one either Z or W.
Sources I have found useful:
http://kippenjungle.nl/sellers/page3.html
(has a list of genes, with their symbols and a little bit about them)
http://kippenjungle.nl/sellers/page2.html
(more information about some specific genes)
http://kippenjungle.nl/breeds/crossbreeds.html
Chicken genetics calculator (There are many slightly-different versions.)
The default has all the genes set to wild-type (what the junglefowl have, marked with +)
You can change any gene in the dropdown boxes, and the little picture of the chicken will change.
It can also calculate what offspring will come from each mating, but I mostly use it to help understand what genes do what.
Yes, the pictures are rather cartoon-ish, but they are good enough to show some things about how the genes behave. For example, if a gene affects just the black on the chicken (Blue does this) or if the gene affects both the gold and the black on the chicken (lavender does this), or if it changes where the gold and the black are located on the chicken (e-locus, Pattern gene, and Columbian are examples of this)
Extended Black is at the e-locus. There are lots of alleles at that locus. All of them affect how the black & gold are distributed on the chicken. Extended Black is the most dominant of them, and "extends" the black to cover the entire chicken. A chicken with Extended Black can have bits of other colors leaking through, but is at least mostly black. Carefully bred black chickens will have some other genes that help make them black all over. A Black Sexlink hen would be an example of Extended Black without the other modifiers (she usually has some red on her chest.)
recessive white is recessive, obviously. A chicken with two copies of the gene (homozygous) will have pure white feathers, no matter what other color genes it also has.
Dominant White changes black to white. It affects all black on the chicken. So an all-black chicken becomes all-white, but a gold chicken with black lacing becomes a gold chicken with white lacing (examples: Buff Laced Polish, White Laced Red Cornish). To get a nice clean white often requires the chicken be homozygous for Dominant White. If it is heterozygous for Dominant White, it will tend to have some black leakage. You can see this leakage in photos of California White chickens, and especially in Paint chickens.
The e-locus affects how the colors are distributed on the chicken.
I suggest you go to the calculator and play around with changing just the e-locus (top gene in the list), and see the effects. All the females are different, although some of the male forms look alike.
Other genes can also affect how the black & gold are distributed on the chicken (examples: Pattern gene and Columbian)
Silver is a dominant gene that turns gold into white. It is on the Z sex chromosome, so males can be homozygous or heterozygous, while females can only be hemizygous. Heterozygous males tend to look a bit yellow, instead of being a nice clean white.
Delawares also have white barring.
Better examples would be Light Brahma, Light Sussex, Columbian Rock, Columbian Wyandotte.
Buff Columbian also exists (example: Buff Brahma, Buff Columbian Wyandotte)
And Red Columbian with Dominant White gives Gold Comets and ISA Browns (plus a multitude of look-alikes with various names.)
That is true for genes on the Z sex chromosome.
It is not true for any other genes.
Yes, but there is a detail your list doesn't mention.
Homozygous pea comb makes the comb & wattles smaller. Heterozygous pea comb does not do that. Any breed that is pure for pea comb will have a small comb and small or apparently-missing wattles. Examples: Brahma, Dark Cornish, Sumatra. Crossing them with other breeds produces hybrids with larger, odd-looking combs, and normal-sized wattles.
r+/r+/P/P will have a small comb and small wattles
r+/r+/P/p+ will have a larger comb and normal-sized wattles
This also applies to Walnut combs-- the ones homozyous for pea comb will have much reduced wattles and small combs as well. Example: Chantecler, Yokohama.
R/R/P/P is expected to have small comb and small wattles
R/r+P/p+ is expected to have larger comb and normal-sized wattles
https://poultry.extension.org/articles/poultry-anatomy/poultry-genetics-an-introduction/ this seems helpful, i skimmed looking at some parts and it seems like some good information. 
Brahmas seem to be the exception here. Males have full sized wattles. I suspect that the reason for this is that it's just another allelic mutation of the pea comb that allows that
There's four combinations for walnut comb.
R/R, P/P
R/r+, P/P
R/R, P/p+
R/r+, P/p+
R/R, P/P
R/r+, P/P
R/R, P/p+
R/r+, P/p+
This boy is an example of R/r+, P/p+
That looks like r+/r+, P/p+ I see the three rows.
I'll have to get a better picture, but I can't right now. My sister will have to for me.
This looks more like r+/r+, P/p+
R/r+, P/p+ will never have three distinctive rows.
I looked at your genetics symbols wrong.
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