Posts Tagged ‘Evolucija’
Why evolution is true objavio je odličan članak o ginandromorfnim kardinalima:
This, by the way, is a very graphic demonstration of the differences between males and females, with the brighter color of the male almost certainly reflecting sexual selection (with bright colors presumably advantageous in males because they attract females, but disadvantageous in females because they attract predators).
Now how does this happen? I used to see this sometimes in my Drosophila flies, and we?ve long known how a half-male, half-female fly forms. In flies the sex is determined by the ratio of X chromosome to autosomes. Flies, like all diploid species, have two copies of every autosome. If you also have two X chromosomes, you?re a female because the ratio of autosomes to Xs is 1:1. If you have one X chromosome and one Y chromosome, your ratio is 2:1 and you?re male. The Y doesn?t matter here: if you lose a Y chromosome, and hence are XO, you still look like a male, although you?re sterile (the Y carries genes for making sperm).