Originally Posted by Kassaundra
This is my understanding of the barred / sex linked connection. All barred FEMALES have a double hit of the barring gene that is why they are darker as chicks and do not have the irregularities in the barring patterning that the males CAN have. Males can have a double hit too, but they will show barring w/ just a single gene those that do will have some irregularities in the barring patterning.
Since the girls need 2 to show, they will pass the one gene to offspring, the boys being solid do not have any barring to pass, so all offspring will only get one barring gene so all barred offspring will be male.
This is just my understanding I don't have any proof or study or knowledge of my own, just what I have surmised from reading, so if inaccurate someone w/ actual knowledge feel free to correct this.
In birds, the females are XY and males are XX*, the reverse of human women being XX and males XY. It's because the Y is much shortened and missing a lot of space for many gene spots.
Like a parking lot that's been half bombed out, so there's much less space to park the cars. The specific parking space for the Barring gene has been bombed out.. so it's "missing" from the Y-parking lot.
In the NN thread, many people are using nn, Nn, NN to mean a non-naked neck, not pure for naked neck(huge bib) and a pure for naked neck(small bowtie or totally clean neck).
Keeping with that theme, the best way to look at sex linked genes is to make a special notation for something sex linked. Since it is "missing" from the reduced sex chromosome, a minus sign is used, -.
B is for sex linked barring, the type on barred rocks, cuckoo marans and Pie.
Roosters being XX means they can be bb(not barred), Bb(single barred) or BB(pure barred).
Hens being XY means they can only be either b- or B-. That's it, no other option..
Rooster: XbXb, XBXb, XBXB
Hen XbY or XBY(no room for barring on Y...)
*in genetics lingo ZZ, ZW is given because they are different. Using more well known human XX, XY example here for explanation purposes only.