As a rule, in mammals, what distinguishes males and females is the existence of two: X and Y. In humans, women carry the XX pair in each of their , while men carry the XY pair.
ZZ or ZW?
In birds, the male or female gender is defined in exactly the opposite way! Females carry the ZW pair while males carry the ZZ pair.W is responsible for female differentiation!
What part of the Yis able to make a little boy out of a fertilised egg? SRY: an amazing . The production of SRY during the very early stages of embryogenesis is enough to trigger off the programme which will eventually form the little boy’s testicles – a characteristic male trait.
What does SRYdo? It binds to and twists it into an angle of 70° to 80°. This angle is important for what follows in the developing embryo. If SRY is modified and thus unable to bind to – or unable to twist the into the correct angle – then what should have been a little boy…becomes a little girl. And this particular little girl will indeed have ovaries, despite the fact that each of her will carry the XY pair…
Is there any scientific instrument capable of measuring the angle produced by the SRYwhen it binds to ? No. In fact, to date, there is no scientific instrument capable of ‘seeing’ the structure of one . So, in order to understand the structure of the SRY when it binds to and to measure the angle it forms, scientists have to use indirect experimental approaches carried out in the laboratory. These approaches locate the position of every single that makes up the , of which there are thousands! Then, by way of high-performance computer programs, scientists are able to visualise the of a .