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Something to chew on ~ chicken genetics
#1
Rosecomb genetics are not quite straightforward. I remember (vaguely) teaching this a few years ago. Had to check it up and for those who want the info. here are a few websites:



http://www.cite-sciences.fr/francais/ala...073_pl.doc (goes into the genetics in detail)



Basically what it is saying is that you can have different comb types:

single,

Pea,

rose,

walnut

The pea type comb is seen in indian game and Brahma types, and according to the article, the rose is 'characteristic of Hamburghs, Rose-combed Dorkings and many other breeds'. If you cross a pea with a rose, you get walnut. So, if the original RIW's were rosecombed, they must have been crossed with something else to lose the rose comb. According to the article, the Malay birds had a walnut comb, so I guess there is something else in the genetic makeup of the RIW's. Just my thoughts!



But then also came across this

http://www.ncbi.nlm.nih.gov/entrez/query...ds=1437982

which _may_ explain why you don't see rosecombs frequently. Have they died out because the rosecomb causes the cocks to be infertile?

Gosh I'm feeling confused now!



Sue
#2
Here's ma diagrams:



How I think sex linking works    













Why the 2nd generation doesn't work the same    
#3
The arrow pointing up is the boy sign, the circle with a cross underneath is the girl sign.



The two birds at the top are the parents, and the letters in them are the chromosomes and the letters assinged to the colour genes.

Each sperm and egg only carries half the genetic info (so when two meet theymake a set to make a chicken), so the circled letters underneath the birds signify the genetic information in the sperm and eggs.

the lines show which ones are joining together and the letters at the ends of the lines are the genetic makeup of the offspring!
#4
A useful link on genetics



I meant this: http://marsa_sellers.tripod.com/genetics...page3.html


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