Male or female? First sex-determining genes appeared in mammals some 180 million years ago

Male or female? First sex-determining genes appeared in mammals some 180 million years ago

The Y chromosome, which distinguishes males from females at the genetic level, appeared some 180 million years ago. It originated twice independently in all mammals. Scientists have managed to date these events that are crucial for both mammalian evolution and our lives, because the Y chromosome determines whether we are born as a boy or girl.

via All Top News — ScienceDaily:

Man or woman? Male or female? In humans and other mammals, the difference between sexes depends on one single element of the genome: the Y chromosome. It is present only in males, where the two sexual chromosomes are X and Y, whereas women have two X chromosomes. Thus, the Y is ultimately responsible for all the morphological and physiological differences between males and females.But this has not always been the case. A very long time ago, the X and Y were identical, until the Y started to differentiate from the X in males. It then progressively shrank to such an extent that, nowadays, it only contains about 20 genes (the X carries more than one thousand genes). When did the Y originate and which genes have been kept? The answer has just been brought to light by the team of Henrik Kaessmann, Associate Professor at the CIG (UNIL) and group leader at the SIB Swiss Institute of Bioinformatics, and their collaborators in Australia. They have established that the first ” sex genes ” appeared concomitantly in mammals around 180 million years ago.4,3 billion genetic sequencesBy studying samples from several male tissues — in particular testicles — from different species, the researchers recovered the Y chromosome genes from the three major mammalian lineages: placentals (which include humans, apes, rodents and elephants), marsupials (such as opossums and kangaroos) and monotremes (egg-laying mammals, such as the platypus and the echidna, a kind of Australian porcupine). …

For more info: Male or female? First sex-determining genes appeared in mammals some 180 million years ago

All Top News — ScienceDaily

Male or female? First sex-determining genes appeared in mammals some 180 million years ago

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