Genetics - so easy even a caveman can do it?

[tiffanyh]

Sounds like your getting it.

buBU could not express as a small butt, if big but it dominant, it will express as big butt.

What are you trying to do with your birds?

 

[DoctorGoose]

Sounds right! Except for the example of a buBu--the dominant gene always goes in front--so it would be Bubu--heterozygous. Recessive genes are never dominant unless the individual is homozygous recessive. Unless the individual is homozygous recessive, the trait will never show up in the phenotype.

Now, if you breed two heterozygous individuals to each other (because just by looking at the bird it is impossible to tell their genotype unless you've bred them)--say Bubu with a Bubu (two people with large butts

!) You'll get (look up punnet squares on Google) 25% of the offspring will be homozygous for large butts (and have large butts); 50% will be heterozygous for large butts (and have junk in the trunk) and 25% will be homozygous recessive for posteriors, having small butts, as only homozygous recessive individuals show the recessive trait.

To find out what's recessive for color, you'd have to look up which traits are recessive/dominant to the other. I'd just google "recessive dominant color trait chicken" and see what comes up. (I found some on Japanese bantams and Polish)

Some more terminology: autosomal--this means that it's passed on to all the offspring. Sex-linked (just like the chickens) these traits are linked to a specific sex--example: balding in men. In conception, women receive two "X chromosomes"--this codes for female. Men receive an X chromosome and a Y chromosome--this codes for males.

Some traits are specifically linked to the Y-chromosome, like balding, and it will only show up in males--this is how some breeds of chickens have very different coloring in the males vs. females, men have manly parts, etc.

Sounds like you're really catching on! This ought to be enough to get you started. Tell us if you have more questions!

 

[Davaroo]

There is a color chart over on EZ-BYC, at this link:

http://p098.ezboard.com/breeding-color-chart/fbackyardchickensfrm3.showMessage?topicID=1911.topic

So what to make of that! Caveman go, ugh!

Oh, and I still wanna know about Jennifer Lopez!

 

[DoctorGoose]

Try this one instead:

http://marsa_sellers.tripod.com/geneticspages/page3.html

I think from the responses on the other thread; everyone was confused--it isn't written properly if you're confused!!

J-Lo....well, it really depends on her children, although sometimes individuals who are homozygous for a trait will display the trait to a higher degree than heterozygous individuals. An example would be pinto horses--some horses who are homozygous for pinto will display the trait to a higher degree--which, in this example, means little tiny spots around the pinto marking....here's a link--check out the second and third pictures http://blacktiearabians.com/tiebreaker/index.html (no affiliation whatsoever, just the first google hit)

Edited to add: I'm not sure if I was entirely clear about sex-links. In some cases, females will carry a dominant gene on one X chromosome, and a recessive gene on another. In these cases, half of their male offspring will have a "sex-linked" trait (I think some may be calling it an "x-linked" trait now.)

This is because if you think about it, females only have the X chromosome to give their offspring. So all unfertilized eggs will have just one X. The sperm, however, has either a Y or an X--and this determines the sex of the bird. Now, if you have an individual who is heterozygous for a sex-linked trait, It must be a female who is heterozygous, males are only homozygous for sex-linked traits, because they only have the one allele!

So, males receive only the X from their mother. So if their mother is heterozygous for a sex-linked trait (e.g. color blindness) This is displayed as X^C X^c(the Cs should be superimposed) Half of her male offspring will have the trait--EVEN IF THE FATHER HAS IT! It doesn't matter for the males if he has the trait or not, because he does not give them that chromosome, at all!

If the mother again is heterozygous for the trait, and she mates with a recessive male (who would then be displaying the trait), half of her male offspring would again display the trait, as well as half of her female offspring.

To breed true in this case, you would have to use two homozygous recessive individuals to get consistently trait-displaying offspring.

*phew* I hope that clears up any confusion

 

[Davaroo]

Uh, I was being cavemannish, Doc - I was referring to J-Lo's ACTUAL nether reaches.

 

[DoctorGoose]

Sorry....lol...I tend to go on...and on....and on....

 

[barg]

In parrots females have XY and males are XX, I didn't go over everything you all wrote and don't know if that is true for chickens, I just thought id toss that out there.

Did anyone bring up modifiers... did I miss it?
An example would be green eyes... or gray parakeets.
A grey parakeet is a blue parakeet with a grey modifier which is also dominant.
If a green bird has the trait they are Olive green, thus proving the evolutionary theory, since there are no wild grey parakeets.

 

[DoctorGoose]

Ah!!! Good call! I never thought to ask if poultry were different. It took some searching, apparently sex chromosomes in poultry is classified information.

http://books.google.com/books?id=__...ts=kbJgeX_ywb&sig=08_HMnNL8LT7xTzHXTNaVrpioQE

The female determines the sex of the offspring! How interesting! Learn something new every day!

 

[horsewishr]

Quote:
Elderoo,
It's not about "position." A dominant gene is dominant and a recessive gene is recessive, no matter what. If you get ONE copy of a dominant gene (from either parent), that gene "dominates" and the offspring will express the dominant phenotype (looks). It take TWO copies of the recessive gene (one from each parent) for the offspring to express the recessive phenotype. (In other words, recessive traits are expressed only when the offspring is HOMOzygous for the recessive trait).

Check out this wikipedia site:
http://en.wikipedia.org/wiki/Mendelian_inheritance

To make matters even less clear, most traits to not follow "simple Mendelian" rules. Many genes interact, so you get things like "dilute factors" which affect color phenotype. (And then there's the whole sex-linked pattern, where genes are carried on the X chromosome . . . )

 

[horsewishr]

barg,

I'm fascincated to learn that genotypic sex detemination is different in birds than other animals! Who knew??!!

I found this explanation on the web:

Many animals, including humans, have a pair of sex chromosomes, designated X and Y, that determine an individuals sex. In humans, individuals with XY chromosomes are male and XX chromosomes are female. The sex of a human baby is determined by the father whether they get an X or a Y. In contrast to this system, birds have sex chromosomes designated Z and W. Males have ZZ and females are ZW. These are the chromosomes used in the DNA sequence probe to determine the sex of a bird. In birds, the female determines the sex of her offspring whether they get Z or W chromosomes.​