Monday, December 14, 2009

Battle of the Sexes - v

I couldn't control myself as the article heading used my regular post caption for the precise reason.

if a specific gene located on a non-sex chromosome is turned off, cells in the ovaries of adult female mice turn into cells typically found in testes. Their study, published in Cell, challenges the long-held assumption that the development of female traits is a default pathway. At the same time, it grants a valuable insight into how sex determination evolved.
In humans and most other mammals, an individual's sex is determined by its sex chromosomes: females have two X chromosomes, males have one X and one Y. Scientists had long assumed that the female pathway -- the development of ovaries and all the other traits that make a female -- was a kind of default: if it had a gene called Sry, which is located on the Y chromosome, an embryo would develop into a male, if not, then the result would be a female. But in adult animals it is the male pathway that needs to be actively suppressed,

I don't think male or female default pathway makes much sense. Or it doesn't at least to me. However, considering the fact that only one of the two X-chromosomes in female is activated, my belief is that genetically male is a high feature being than female. In other words, male is naturally both male and female but female is only female and wannabe male. In a different way, the present study also supports this position.

Via Science Daily


Maju said...

I read about this. It might be a very much pre-human evolution (generically mammal?, older?) pathway.

In other taxons like reptiles or many fishes, gender is not controlled by the sex chromosomes but by environmental cues, sometimes in the egg, sometimes even in adult life (some fishes change sex).

I watched some documentary on hermaphrodite invertebrates where the mating act is a true fight... to determine who is the male (winner) and who the female (loser). The female role is obviously less productive in genetic terms and is also more demanding in most species. However male-only species just can't exist.

It's also interesting that the pathway is signaled by a diploid chromosome.

manju said...

However male-only species just can't exist.

Iberian minnow. Something close to your home.

Maju said...

Pretty weird and worth reading... but the phrasing is tricky: clearly there are females with whom they reproduce. Not just that: first they must reproduce with "non-hybrid" female in order to create a "hybrid" female. You can also consider the hybrid as part of the "male-only" species or, rather, all as single species with a complex sexual structure.