How do genetics work?

[Chicks n stuff]

There are two "layers" that influence shank color.
Dermis is the underlying skin structure & tissue.
Epidermis is the skin that covers over the Dermis.

Skin/Leg:

Fm(Fibromelanosis/dark skinned/dark shanked)- autosomal, dominant, with multifactorial modifiers. As seen in silkies.

The EpiDermis Layer has the following colour options. W+/W+= white shanked, W+/w=white shanked w/w + Id=yellow w/w + id+=willow shanked

w(Yellow-skin/yellow shanked/willow-green -shanked)- autosomal, recessive.

W+(white skin/white-shanked)- autosomal, dominant.

y(sexlinked/white-skinned/white-shanked)- sexlinked, recessive.

The Dermis Layer has the following colour options. Female Id/-=white shanked, male Id/Id=white shanked, female id/-=dark shanked, male id+/id+=dark shanked.

Id(dermal melanin inhibitor/ Light/white-shanked)- sexlinked, dominant. Carried on the Z sex chromosome.

id+(dermal melanin/slaty blue-shanked)- sexlinked, recessive. Carried on the Z sex chromosome.

W+ + id+(slaty-blue-shank)- (W+autosomal), (id+sexlinked),(W+dominant), (id+recessive).

w + id+(willow-green-shanked)- (W+autosomal), (id+sexlinked),(W+dominant), (id+recessive).

W+ + Id(white-shank)- (W+autosomal), (id+sexlinked),(W+dominant), (id+recessive).

w + Id(yellow-shanked)- (W+autosomal), (id+sexlinked),(W+dominant), (id+recessive).

Some foundation colors and secondary color genes can change skin and shank color. Without extensive research and testing I would recommend avoiding these genes when choosing a shank color sexlinked breeding stock. That is not to say say that you can't make shank color sexlinks with a black or slash or recessive white chicken, but the exact effects these feather color genes have on shank color must be determined and understood before you do.
People not fully understanding the correlations between certain feather color genes and shank/sink color genes is why many people think shank color sexing is a myth. While it isn't a myth, shank color sexing is fairly complicated.

Factors That Enhance Black Dermis Color.
E/E (Extended Black)
ER/ER (Birchen) (Enhances to a lesser degree than E/E)
Black with white soles=W+ + id+ on E or ER
Black with yellow soles=w + id+ on E or ER

Factors That Dilute Black Dermis Color.
Bl/bl (Blue)
Bl/Bl (Splash)
c/c (Recessive White)
mo/mo (Mottling)
I/I (Dominant White)
Di/Di (Gold Dilute)
Male B/B, female B/- (Barring/cuckoo)-the barring gene is found on the Z sex chromosome. A barred chicken breed is easier to shank sex, males will have lighter shanks thanks to having a DF of the barring gene.

Please note that this is only the case when you have developed an auto-sexing shank, an auto-sexing shank would be maintained in a breeding line of a purebred breed. The barring gene could potentially be beneficial or complicate things if you are making a shank color sexlinked cross. A shank color sexlink would be sexable for a single crossing, just like every other type of sexlinked cross. In a shank color sexlinked pairing, the rooster would id+/id+ and the hen would be Id/-(as she only has the one Z sex chromosome), all female offspring would inherit an id+ from their father and the W sex chromosome the female inherits from her mother won't influence shank color, making females id+/-. The male offspring would inherit his mother's single Id gene from her Z sex chromosome, and one of his father's id+ genes, meaning the male offspring would be Id/id+, meaning males would have a white or yellow shanks, and females would have a slate/blue/dusty white or willow/dusty yellow shanks, provided they aren't E(dominant black), or ER(birchen) base color.

 

[talkinboutchickens]

Size:



adw(autosomal dwarfism)- autosomal, recessive.

https://pubmed.ncbi.nlm.nih.gov/11092317/





dw(sexlinked dwarfism)- sexlinked, recessive.



dwB(bantam dwarfism)- sexlinked, recessive.



Cp(Creeper/short legs)- autosomal, dominant, LETHAL.



https://go.gale.com/ps/i.do?id=GALE|A218450175&sid=googleScholar&v=2.1&it=r&linkaccess=abs&issn=10112367&p=AONE&sw=w&userGroupName=tel_oweb&isGeoAuthType=true&aty=geo





Trait:



M(multiple spurs)- autosomal, dominant.



Po(Extra toes/polydactyl)- autosomal, incomplete dominant, expressivity and penetrance extremely irregular.



0(Blue egger)- autosomal, dominant.



br(brown eyes)-sexlinked, recessive.



Comb:



bd(Breda comb/Combless)-autosomal, recessive.



DV(V-shape Duplex comb)- autosomal, incomplete dominant.



DB(Buttercup, Duplex comb)- autosomal, incomplete dominant.



R(Rose-comb)- autosomal, dominant.





P(Pea-comb) - autosomal, incomplete dominant.



R+P(Walnut-comb)- both autosomal, both dominant.



Feathers:



h(Silky)- autosomal, recessive.



F(Frizzle) autosomal, dominant, semilethal.



Na(Naked neck)- autosomal, dominant.



K(late/slow feathering)- sexlinked, dominant.

https://pubmed.ncbi.nlm.nih.gov/2837753/





k+(rapid/fast feathering)- sexlinked, recessive.



Hf(Henny feathered)- autosomal, incomplete dominant, sex-limited.



Pti(Featherfooted)- Autosomal dominant with multifactonal

modifiers (possibly 2 or 3 loci).



v(Vulture hocks/longer leg feathers at the elbow of the leg)- autosomal, recessive.



Mb(Beard)- Autosomal, incomplete dominant, incomplete penetrance.



Cr(Crest)- autosomal, incomplete dominant.



Wc(white crest)-autosomal, incomplete dominant.



Lf(LONG FLOPLUMES)- autosomal, dominant.



mt(non-molt/long tail)- recessive.



Gt(NON-LIMITED GROWTH/long tail)- dominant.



Et(Eartufts) - autosomal, dominant, incomplete penetrance

and irregular expressivity, lethal?



Rp(Rumpless)- autosomal, dominant, lethal?



Skin/Leg:



Fm(Fibromelanosis/dark skinned/dark shanked)- autosomal, dominant, with multifactorial modifiers. As seen in silkies.



w(Yellow-skin/willow-green-shanked)- autosomal, recessive. Willow green like you can see on Easter eggers.



W+(white skin/white-shanked)- autosomal, dominant.



y(sexlinked/white-skinned/white-shanked)- sexlinked, recessive.



Id(dermal melanin inhibitor/ Light/white-shanked)- sexlinked, dominant.



id+(dermal melanin/slaty blue-shanked)- sexlinked, recessive.



W+ + id+(slaty-blue-shank)- (W+autosomal), (id+sexlinked),(W+dominant), (id+recessive).

So fluffy cheeks won't appear in offspring? What does autosomal and incomplete dominance mean?

 

[NatJ]

What does autosomal and incomplete dominance mean?

Autosomal genes are all the ones not on the sex chromosomes.

So when the list has "sex linked dwarfism," that gene is on the Z sex chromosome.
The list also has "autosomal dwarfism," which is a different dwarfism gene, and is on one of the other chromosomes (not the Z sex chromosome.)

Referring to them that way makes it very clear how each is inherited: one is a sex-linked inheritance pattern, the other is not.

Incomplete dominance:

A gene that is incompletely dominant will have a noticeable effect if the chicken has one copy of the gene, but a bigger or different effect if the chicken has two copies of the gene.

The gene for blue feathers is incompletely dominant. A chicken with one blue gene will have all the black in their feathers diluted to blue (a shade of gray.) A chicken with two blue genes will have all the black in their feathers diluted to splash (a much lighter shade of gray, often with "splashes" of black or blue present as well.)

The pea comb gene is incompletely dominant. One pea comb gene will make the comb a different shape (as compared with a single comb.) Two pea comb genes will change the shape a bit more, and make the comb smaller, and also make the wattles smaller.

For comparison, the rose comb gene is just plain dominant, no "incomplete" about it. A chicken with one rose comb gene looks the same as a chicken with two rose comb genes. There is no visible difference. It is fairly common for chickens with rose combs to produce chicks with single combs, because the chicken can have a rose comb will carrying the recessive gene for not-rose comb, and you just cannot tell (except by seeing that some of its chicks have single combs.)

So fluffy cheeks won't appear in offspring?

I don't quite understand what you are asking. What parents would you be dealing with?

If both parents have clean faces (no fluffy cheeks), then the offspring should all have clean faces too. But if one or both parents have muff/beard (the gene and the visible effect), then at least some chicks should have it too.

 

[talkinboutchickens]

I don't quite understand what you are asking. What parents would you be dealing with?

An easter egger hen with a muff/beard and a sapphire gem rooster.

 

[NatJ]

An easter egger hen with a muff/beard and a sapphire gem rooster.

From that pair, I would expect either half or all of the chicks to show muff/beard.

If the hen has one muff/beard gene, half of the chicks inherit it from her.
If the hen has two muff/beard genes, all of the chicks inherit it from her.

Either way, a chick with one muff/beard gene should show the trait, because it is dominant.

I've read that muff/beard is incompletely dominant: bigger muff/beard with two copies of the gene. And I've read other sources that say it is completely dominant, producing the same result whether the chicken has one or two copies. Those sources say the size of the muff/beard is determined by some other genes, not by how many copies of the muff/beard gene the chicken has. I do not have enough experience to say which view is correct. But they both agree that chicks with one muff/beard gene can be expected to show at least some amount of muff & beard.

 

[talkinboutchickens]

From that pair, I would expect either half or all of the chicks to show muff/beard.

If the hen has one muff/beard gene, half of the chicks inherit it from her.
If the hen has two muff/beard genes, all of the chicks inherit it from her.

Either way, a chick with one muff/beard gene should show the trait, because it is dominant.

I've read that muff/beard is incompletely dominant: bigger muff/beard with two copies of the gene. And I've read other sources that say it is completely dominant, producing the same result whether the chicken has one or two copies. Those sources say the size of the muff/beard is determined by some other genes, not by how many copies of the muff/beard gene the chicken has. I do not have enough experience to say which view is correct. But they both agree that chicks with one muff/beard gene can be expected to show at least some amount of muff & beard.

Oh got it! That makes sense. Thanks for clearing things up!