what determines gender?

Actually, in chickens, the hen determines the offspring's gender--just the opposite of humans.

 

Really? That's very interesting! How does that work?

 

Birds
Next, approaching birds, we begin to tread on more familiar ground, as once again we return to sex chromosomes. In birds however, females are the heterogametic sex, carrying one copy of each of the so called Z and W sex chromosomes, whereas males are homogametic ZZ. The Z and W chromosomes have no relation to the mammalian X and Y, and in fact seem to have evolved from different pairs of autosomes. And this is part of the reason we are not yet certain which of the two carries the genetic trigger for sex determination [38,39].

To this day, there are two major theories under investigation. Sex may depend on Z chromosome dosage, according to the example of Drosophila melanogaster and C.elegans. One candidate gene for this theory is the DMRT1, which is located on Z chromosomes, escapes dosage compensation and is expressed specifically in the gonads, and is thus capable of linking the number of Z chromosomes with gonadal differentiation [40,41].

On the other hand, sex may be determined by the feminizing presence of the W chromosome, following the example of Y in eutherian mammals. There are two different mechanisms that are being studied and can support this theory. One includes the FET1 gene, which is located on W, does not have a Z homologue and is expressed almost exclusively in the female urogenital system [18]. The other includes the ASW gene, also known as WPKCI, and its Z homologue ZPKCI, since it has been proposed that the products of those two genes are capable of dimerisation, with a ZPKCI homodimer acting as a testis factor and a WPKCI/ZPKCI heterodimer preventing this effect (see Figure 14) [39-41].

http://www.rbej.com/content/4/1/59
From:
Molecular patterns of sex determination in the animal kingdom: a comparative study of the biology of reproduction​

 

That is great info DuckyBoys , but allow me to translate that to English for the folks down home

Okay, so, the roo has sex chromosomes ZZ and the hen has ZW. This is similar to, but different from, the human XX and XY. For all intents and purposes, though, it works in a similar way. If the chick gets a Z from momma, it's a roo. If it gets a W, it's a hen. They don't know if it's because it takes a lot of Z to make a roo, or if the W is a special hen-making chromosome. Either way, the effect is the same, and the W makes a hen.

Btw, I've read that good nutrition can make a slight difference in the number of female offspring produced in some bird species (that is, you get a few more females when hens are well fed). Don't know if it applies to poultry, but it might be one more good reason to feed those chickens well

 

Quote:I hope I get those results. Of my straight run purchases I got almost all roos. I have my first hatch due Monday from my own hen and Wed. from my purchased fertile eggs. I was told it was incubator temp that determines sex. Glad you asked the question and got anwsers so I could learn also.

 

I was told a old wise tale but a lady I got my dorking eggs from. She has been experimenting with it for 2 years and has a 98% success rate for hens. She was told that the eggs with a point to the small end was roo's and when the small end of the eggs is oval or rounded they are hens. She swears by it. Me I am keeping track of my oval and round eggs verses my pointed eggs and I will see. Just thought ya might want to know in case ya want to try your hand at seeing if it is true.