Does Anyone Know Chicken Genetics?

[so lucky]

I am wondering what the offspring would be if you mate a bantam rooster to a large breed hen. Would the eggs be full size or bantam? Would the chicks be full size or bantam? Would it be a mix? If the eggs are large, would a full size chick be hatched? I could probably find the answers over on BYC, but there are too many postings to wade through there.

 

[vfem]

It depends on the breeds. Its based on whether a bird's genetics are dominate or recessive. If the roo is rather large, but carries the gene for a smaller size and then passes that gene off with a bantam hen, then the offspring could be a small or medium size. The egg size will really depend on the bird's final size. You can have small, medium or large egg layers.

Most the info I can find on true genetics are actually based on colors strains in the dna. Here's a color genetics calculator that will explain the offspring based on that:

http://kippenjungle.nl/kruisEmbedArray.html

But when it comes to size... the parents will share, and you are more likely to get a medium sized birded.

 

[so lucky]

So I suppose that if one uses birds that have been bred true to type for several generations, the liklihood of a recessive gene coming out is less?

 

[vfem]

So I suppose that if one uses birds that have been bred true to type for several generations, the liklihood of a recessive gene coming out is less?

Well not really... some genes are always recessive. Plus, you can get multiple recessive genes for different things. Like Comb type, body type, color. You never know what will transfer to the off spring that way.

This is done normally be breeders who are trying to breed and bring a standard size bird into a bantam size. Breeding this way was done to miniturize many of the current bantam breeds. So I'm guessing breeding between a bantam roo and a stardard, then breeding the father to the child offspring, then breeding again.... ect. I don't think the original offspring was ever considered a full bantam of the size. It took many round of breeding to get the smallest bird they could accomplish, and then breed to that.

So I'm assuming we are talking the first generation offspring?

 

[Kassaundra]

First things first, are you sure he can fertilize the eggs? There may be size related fertility issues if he can't mount properly.

 

[Ridgerunner]

Both parents will contribute genes that affect egg size, final body size, all of that. Some genes are dominant, some are recessive, some are partially dominant, some are incomplete dominant. Usually there are a whole lot of different genes that have an influence.

Maybe a couple of examples to help explain this. These examples are about egg shell color and feather color but the principles apply to egg size, body size, and about anything else.

Egg shell color. There is one gene that determines if the base color of an egg shell is blue or white. Blue is dominant so if just one of that gene pair is blue, the base color is blue. But there are over a dozen different genes that determine the shade of brown that is put on the egg and that is just the ones that have been identified. Who knows how many have not been identified? Brown is just brown over white. Green is just brown over blue. If no brown is present then there is only blue or white.

But how those different brown genes mix together determines which actual shade of brown shows up. Its not just dominant or recessive. How much or what influence they have is determined by what other genes are there as well as if they are dominant or recessive.

Blue feather color. If you have two copies of the blue feather gene, you get what is called Splash. That's a black and white mix. If one of the genes at that gene pair is blue and the other is not-blue, then you get blue. If neither of that gene pair is blue you get black. But theres a bit more to it than this. This only affects the feathers that would normally be black. If you have a solid white or red chicken, the Splash, Blue, or Black wont show up. It makes no difference if the blue gene is there or not. Or if the chicken would normally have a black tail, then the tail is the only feathers affected.

There are a lot of genes that affect body size and shape and egg size. What effect the ones present have depends onwhat other genes are present. The possibilities are tremendous.

As a side note, a rooster contributes as much or more than the hen to egg size, egg color, frequency of laying, any of that. A rooster gives a gene from every gene pair he has to all his offspring, including genes related to egg laying. A hen gives her all to her sons but withholds the sex linked genes from her daughters. The hen is the one that controls the sex of the chick, not the rooster.

When you cross a bantam with a full sized chicken, the results will normally be somewhere in the middle. Whether they are closer to the bantam or the full sized chicken depends on which genes get passed down. A lot of the chicken genetics are sort of scrambled anyway. Thats why even with purebreds bred to purebreds you can get a variety of body size and shape, egg size and shade of brown. So even with the same parents crossing a bantam with a full sized chicken you can get some pretty different results. If you then breed that offspring to other offspring or full sized or bantam you can really get some different results.

The size of the hatched chick is going to be determined by the size of the egg. An egg only holds so many nutrients. A small egg does not contain enough nutrients to grow a big chick. If it did, that chick would not have enough room inside the egg to position itself to hatch anyway. The size of the hatched chick does not control the size of the grown chicken.

So I suppose that if one uses birds that have been bred true to type for several generations, the liklihood of a recessive gene coming out is less?

Sorta, kinda. Inbreeding, which is how you get true to type or show quality chickens, is used to eliminate recessive genes they dont want, so your basic statement is true. But when you outcross, like a bantam to a full sized chicken, you are stirring the gene pool. In many ways you are starting over.

The more inbred they are the less genetic diversity they have so the more consistent the offspring will be. But there are a whole lot of genes involved. The best Ive heard from people really good at breeding show quality chickens is that maybe 1 out of 5 hatched chicks is truly show quality. After many generations of breeding to get rid of genetic diversity so the traits inherited are only the show quality traits, they just cant seem to regularly get over that 1 to 5 ratio. There are probably people out there that have, but I havent seen them say it.

 

[so lucky]

Wow. Thanks, everyone, for your educated responses. I should have paid more attention in biology class when we talked about fruit flies and Mendel's peas.
I'm not in a position to be trying to breed for a new breed or size of chicken. I have just been thinking I would love to have a broody and a rooster, as I do have room for some more chickens. I was just wondering if I found a bantum roo in a type I like, how that would go with the LF girls I have. I have been wanting some marans, but they are scarce around here. Was thinking about bantam cochins, instead. Just thinking with my keyboard, kinda.

 

[canesisters]

If you can figure out a way to get him, I'll GIVE you my marans roo.


eta:

 

[so lucky]

Yeah, a roo when you don't want a roo is a big pain in the neck. I had a White Rock, and gave him away. Wonder if a bantum is easier to drop kick if need be?:/

 

[baymule]

If you can figure out a way to get him, I'll GIVE you my marans roo.


eta: http://www.theeasygarden.com/forum/uploads/8721_hurra_11213_3.jpg

Marans and dumplings??