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Discussion in 'What Breed Or Gender is This?' started by pa2chitown, Dec 3, 2015.
Honey, I don't know you so it can't be personal.
Maybe you can enlighten us on exactly what genes you're talking about, and how they would be transmitted in this breeding, and why they would make this chick a female. We always love to learn.
What sex-linked dominant gene is present here?
Ok, sorry. I just wanted this to be conjecture and not a situation where people are taking sides on who knows more? That is why i have a "poll". I posted the link that is in this site regarding the characteristics in question: head color and leg color.
I learned a lot about genetics as a child, raising chickens. Then i got a masters degree in genetics (nothing to do with chickens). Then i stopped doing scientific work. I havent had chickens for about 30 yrs, until recently, and havent worked in the science field in almost 10. Im surprised that the field of genetics in chickens is not dissected better by the scientific community, as far as i can tell???
I mean, the field has commercial value, and just doesnt seem to have progressed like some other fields of genetics....but maybe i didnt search hard enough?
My point is this:
It doesnt seem to be known for sure if "sex-linked dominant" genes are literally that, or whether they are "partial dominant", which would mean that the phenotype (how the chicken looks) can vary based on other genes present in the sex. If phenotype is strictly due to sex-linked dominant genes, any variation between male and female is purely a reflection of the gene being expressed differently in the sex and not a heterozygous genetic variation...
Is this the kind of information you're looking for?
This only works if both parents are barred, and it's still mostly just guessing.
I said in my first post, since the bird does not have two barred parents, you can't sex it by the normal "rules" of sexing pure bred barred birds. That the bird only has one barred parent makes that link you posted a moot point. The rules simply don't apply.
A pure bred (homozygous) barred male, which we'll assume your Dominique is, will throw all barred chicks, regardless of gender. A homozygous male gives one copy of the barring gene to each offspring. A female barred bird can only be heterozygous, and can only pass the barring gene to her sons.
So, your Dominique male over a non barred female will give all hetero barred offspring. There's no way to tell a hetero barred male from a hetero barred female by color. They're identical with regards to size of head spot, amount of black vs white barring, and the dark wash of color on the legs. The ability to sex pure barred birds is based on the males being homozygous and the females being hetero. Being homozygous for the barring gene is what gives the males the more white vs black, the larger, messier headspot, and the pure yellow or white legs.
With your cross, you'll have to wait for sex characteristics to develop, such as comb size and color, leg thickness, and eventually sex feathers. Your males will also usually mature with messier barring and leakage of the base color (silver or gold) in the sex feathers and on the wing bow, but by the time that happens you should be well able to tell males from females.
If you were to reverse your cross, and put a non-white, non-barred rooster over a Dominique or other barred hen, you'd get sex linked offspring that are easy peasy to sex at hatch. Headspot would mean male, solid head would mean female. The males would all be hetero barred, though, and if you didn't know their parentage they could easily pass for pure barred female chicks at hatch. Until those combs start growing......
...then "sex linked dominant" is not correct. If what you people are saying is true, then it is "sex linked recessive" OR a "partial dominant allele".
Sex linked, in birds (most) means that the MALE always contributes one copy of the gene or 'chromosome'. The female contributes one copy to male offspring, so the male has two copies but if one is dominant it will be expressed over the recessive in a phenotype when it can be visualized as a " trait".
So, one copy, or heterozygous dominant, is all that is required.
In female offspring, there will ONLY be one gene regardless. So, you will always see a phenotype, or trait, when you only have one copy anyway. So, you will have the same phenotype as you would if both parents had the gene whetger homozygous (male) or hemizygous (female).
What is being lost is that im telling you guys that be definition, you only need one copy of the gene in a "sex linked dominant" situation. Either the term is a misnomer and incorrect OR you CAN determine sex ANY time the sex linked dominant gene is present.
No matter how many times people tell me it cant be done, i will still have the same answer because that is how genetics work. If the terms are not accurate, then it is just a terminology issue.
Nobody is saying anything new. I understand genetics
In other words, i knew that the chick just hatched would be the color that it is (phenotype). I know that EVERY chick that has one copy (or two) of the Sex-linked Dominant gene for feather & leg color on the sex chromosome WILL look like the one that just hatched.
Since it IS established that sex can be determined using these traits, it will be true regardless (as long as one or more copies of the sex-linked dominant gene is present).
NOW, if the term "sex linked dominant" is used incortectly, then all bets are off. But nobody is clarifying this
The females will always have the same phenotype when the single gene is present because they only get one chromosome (although a tiny fragment of a second chrimosome does exist).
Now, males will show the phenotype when one copy is present, IF it is "dominant". If it is partial dominant or has a cumulative effect then the phenotype will not be useful to determine the sex. If this is true, then " sex linked dominant" is not the right term OR, if cumulative, then THAT solves it!
I'm seeing a contradiction in the bolded text. You say every chick will look like the one hatched. that's true if they have ONE copy of the barring gene. If they have TWO copies, they'll look different, but the difference is subtle and takes a developed eye to see.
If every chick (male or female) will look like that, how can you determine gender? You've still not explained that.
Yes, barring is dominant. Your chick is barred. That's a no-brainer. But barring isn't the only gene in the world where a double dose expresses stronger than a single dose. The next most common example in the chicken world is the genetics of black/blue/splash. I feel you're willfully not seeing that and getting tied down in semantics.
I've been raising birds for over 20 years. the last five years I've focused on the barring gene in black and blue birds. I've bred several different combinations, with actual birds on the ground. I've done tons of research in the practical application of the barring gene. It's kind of my thing and as far as I've posted here, I know whereof I speak.
You are adding words to my mouth, but FINALLY giving some empirical data.
(Just because I say, they will all look like that does not mean I am stating that they can be sexed. That is the question. Taking a few words out of the post, and not relating them to the rest of the post is out of context.)
Look the first reply was wrong, and everyone was agreeing. Ok. That is number one. The first post alluded to being able to tell if it is a male under certain heterozygous conditions. This would NEVER be the case. The FEMALE phenotype will be determinable for sure, when only one sex gene is available...but this will not help determine sex, if males look like females too...
It doesn't appear that "dominant" is the right term. Of course there are examples of dosing, however I see NOTHING in the literature for this discussion. That is something that I referred to in saying that chicken genetics seem to be lacking comparatively? A female with ONE dose of a sex-linked dominant gene (100%) has more black on the legs than a male with two copies (100%)? That means that there are OTHER genes involved... IF that is the case, THERE are other subtle things that should be observable. The female with ONE copy, and ONLY one copy will look the same regardless of whether the father was homozygous or heterozygous. Now, using the FEMALE as the standard, you could look for "dosage" dependent differences in leg color:
-My chick has VERY dark legs, possibly darker than a female should have. Could this be caused by the "slate" leg color of the EE? If YES, then I have a male. EE sex-linked "black" leg color gene from mother x Dom "Yellow" Dominant sex-linked gene from father... So, IF there is DOSAGE effect and there are other alleles involved in leg color, you should be able to see subtle differences, as long as you understand genetics.
THIS is something that should NOT be "oh, i've been doing it for years, so I'm right". If the world worked that way we'd all be in trouble.