Half-Male, Half-Female Fowl Explain Birds' Sex Determination

Kanan excerpts from a BBC report out of Scotland: "A study of sexually scrambled chickens suggests that sex in birds is determined in a radically different way from that in mammals. Researchers studied three chickens that appeared to be literally half-male and half-female, and found that nearly every cell in their bodies — from wattle to toe — has an inherent sex identity. This cell-by-cell sex orientation contrasts sharply with the situation in mammals, in which organism-wide sex identity is established through hormones." Kanan also supplies this link to some pictures of the mixed-cell birds.

Comments

About one in every 10,000 chickens is gynandromorp

[kimvette]

About one in every 10,000 chickens is gynandromorphous, to use the technical term.

That's somewhat close to the rate of intersex conditions in mammals, including humans.

Re:Interesting

[RCGodward]

I think this story is for the birds... I'm sorry...

Object-sex-oriented?

[InsertWittyNameHere]

So each cell has it's own this.getSexualOrientation() function.

Whereas mammals have a global static variable where SEXUAL_ORIENTATION = MALE or FEMALE.

This is interesting because I thought we all inherited from a common ancestor. Was sexual orientation not defined in the root class?

Re:Object-sex-oriented?

[Anonymous Coward]

Sex is what you have between your legs.
Gender identity is what you want between you legs.
Sexual orientation is what you want between someone elses legs.

Re:Object-sex-oriented?

[FlyingBishop]

In both cases, each cell has its own this.getGender() function.

In both cases, I would imagine the code looks something like this:

class cell {
      int gender; // should really be a bool, need to fix that at some point.
      proteinFactoryBuilder asdf; // find a better naming scheme ... ...

      getGender() { /* I don't really have time to go back and fix this right now, but if I'd known I'd be making multicellular organisms with this shit I wouldn't have put this at the cellular level. Anyway, we're stuck with it, so for now I'm just returning the gender variable and I'll leave it to callers to figure out wtf to do with unexpected output. */
          return gender;
      }
}

Small wonder it's a little more confusing for birds.

Re:Object-sex-oriented?

[reverseengineer]

Mammals actually handle sex inheritance in an inverted arrangement from birds. Whereas mammals use the X/Y system, where males are the heterogametic type (XY) and females are the homogametic type (XX), birds (and some other animals) use a "ZW system" where males are ZZ and females are ZW. A notable feature of ZW determination is that the Z chromosome is more like a full-fledged chromosome with many genes, unlike the mammalian Y chromosome which has been paring down its genes so that it contains the sex-determining gene SRY, some genes necessary for sperm production, and little else.

This might go a long way towards explaining gynandromorphism in birds. In mammals, maleness is handled in a top-down fashion- the Y chromosome does not explicitly specify most aspects of the male phenotype, instead simply encouraging the cells that go on to make androgens, which then go on to produce a cascade of developmental effects throughout the body. In birds, the Z and W chromosomes both may have enough genes that sex determination can be handled from the bottom up, locally in each cell.

Re:Object-sex-oriented?

[Chris Burke]

Don't be silly.

Sex is what you want but can never get enough of.

Gender identity is what lets you pick out cross-dressers and transvestites.

Sexual orientation is how you're oriented during sex, i.e. missionary, doggy style, reverse cowgirl, Saskatchewan Swinging Simian power retrograde style, etc.

n00bs

[DriedClexler]

They're not the first ones to be checking out a nice-lookin' bird and then see from another angle that "she" is really a man.