Tell me about tuft genetics

[Trish1974]

I am looking at getting some non-tufted araucana pullets. Their mother was tufted, their father non-tufted. The breeder said all but 2 eggs from her batch hatched, and they were all non-tufted. The two that died in shell was not far enough along to tell if they were going to be tufted.

I would have thought her hatch would have been 50% tufted, 50% non-tufted.
So...
1.) Is non-tufted dominant over tufted?
2.) Mom had small tufts...does that make her tuft gene weaker than if she had big flowing tufts?
3.) My rooster is tufted. Since the pullets are non-tufted does that mean I have ZERO chance of the offspring having the fatal double tufted gene, or can that pull from deeper in the genes (meaning since mom was tufted can that gene surface, mix with my double tufted male gene and possibly make the fatal gene?)

Any other info you can tell me about tufts would be greatly appreciated.
Thanks!

 

[Sneebsey]

Tufts are an incomplete dominant gene, so one copy of the gene gives you tufts, two copies results in a dead chick (it is lethal in its pure form). Non-tufted birds, like the two pullets, have no copies of the gene, it is not present.

Breeding your tufted cockerel to the non-tufted pullets will result in around 50% tufted single-copy, and 50% non-tufted, though the numbers may not add up until you're talking about hundreds of offspring; it's just statistics.

So in answer to #1, tufted is incompletely dominant over non-tufted; a single copy of the gene gives a different result (tufting) to two copies (dead).
In answer to #3, none of the offspring from your tufted cockerel and non-tufted pullets will get two copies and die in shell as a result.

#2 is an interesting question, and I can't think of an answer to that; I think it's just the way that genes can combine differently to create a different phenotype.

 

[Ridgerunner]

Trish you have to have enough numbers for averages to mean much. I'm not sure how big that sample size was. The 50% is per chick, not for the entire hatch. It's like me getting 7 pullets out of 7 chicks that hatch. The odds are against it but it happens.

The tufted gene is dominant (well, incompletely dominant as Sneebsey pointed out but consider it dominant as far as showing up or not if it is present). There are probably other modifying genes that determine how big they are since you can get some pretty wild ranges. It's like egg shell color. There is one gene pair that determines if the base color is white or blue, but a lot of different modifiers that determine the shade of brown or green if brown is present. As wide a range as you can get with the tufts there have to be modifiers somewhere.

Since tuft is dominant and it is not a sex linked gene, let's use "T" for tuft and "t" for not tuft. You cannot have a living bird with TT at that gene pair as it is a fatal gene. Therefore any tufted bird is Tt. Since it is dominant any non-tufted bird it tt. Sometimes those tufts can be a bit hard to see though.

If you cross a Tt bird with a Tt bird 25% will be tt or clean faced. 50% will be Tt or show tufts. 25% will be TT and die in the shell.

If you cross a Tt bird with a tt bird, 50% will be Tt and tufted, 50% will be tt and clean faced. So with your tufted rooster and non-tufted pullets you cannot get a double dose of the fatal tufted gene.

 

[Trish1974]

Ahhh I get it now. Thank you both very much!

 

[Trish1974]

Sorry to rehash this old thread, but I have two other questions related to rumpless araucanas:

The random tails that pop up in the breed...what is the frequency of that? There doesn't seem to be much info around regarding that topic. All I have to go off of is a lady I know has hatched about 30 eggs from two different sources and she has only had one partially tailed araucana out of the bunch.

Also, just to make sure I got the previous posts understood... you can NEVER get a tufted bird from a tt x tt pair, even if they had tufted parents or grandparents?

 

[Ridgerunner]

The random tails that pop up in the breed...what is the frequency of that? There doesn't seem to be much info around regarding that topic. All I have to go off of is a lady I know has hatched about 30 eggs from two different sources and she has only had one partially tailed araucana out of the bunch.

I don't know enough about the genetics of the tails to know what is dominant or recessive or even partially dominant. My guess is that one of her sources may not have been as pure as she thought, though something like that happens occasionally from some pretty pure sources. It is hard to know when you have gotten rid of all recessive genes. Recessives can be quiet for generations.

Also, just to make sure I got the previous posts understood... you can NEVER get a tufted bird from a tt x tt pair, even if they had tufted parents or grandparents?[/QUOTE]

If the gene is not there it cannot miraculously appear. If neither parent has it then it cannot show up in their offspring. As I mentioned above sometimes those tufts can be pretty hard to see.

 

[Sneebsey]

Rumplessness is dominant, I believe, therefore one copy of the gene gives the same result as two; rumplessness. With that in mind, two birds with only one gene each for rumplessness would hatch about 25% normal tailed offspring. That is likely where the tails are coming from.

You can never get tufted from non-tufted, unless a mutation occurs, which is extremely rare. With that said, I have birds which I know to have single-factor muff-beard (different gene, I know) who display no beard whatsoever (but lack wattles, as a bearded bird does), therefore it could be that your bird does have the gene, but it is not displaying as normal. A lot of genetics is down to chance.

 

[Trish1974]

Thank you both. So it sounds like getting the partially tailed birds is out of anyone's control; which is why I guess even the top breeders state this as a disclaimer when selling hatching eggs. I have read some people (I won't call them true breeders) prefer a tailed rooster because they say it helps with balance while mating. I don't think I would want the increased odds of getting tailed offspring, though.

The pullets I had planned to purchase at the origin of this thread did not pan out. Other things have changed and I have decided to start one or two breeding pens next year. I know I definitely want a silver duckwing trio, and perhaps a cuckoo trio. So as far as tufts go, I assume I want my trios as a tufted rooster with non-tufted hens, or a non-tufted rooster with tufted hens to get the best results?? (Best results meaning most tufts without dealing with the fatal gene).

 

[Sneebsey]

Yes, a bird with only one copy of the rumpless gene will display the same as a bird with two copies, therefore a wildtype (tailed) gene can be carried down the generations without being seen until two carriers breed together.

I personally agree that I would not want to lose 25% of offspring to the double-dose of the tufted gene, so would breed as you plan to, tufted to clean. The non-tufted birds you hatch can still be used in breeding or sold as pets.