Evolution Connection Biologists believe that the X and Y chromosomes were once a fully
homologous pair. Indeed, it is believed that they evolved from an autosomal pair approximately
300 million years ago. Over the years, many genes have disappeared from the Y causing it to
shrink. Additionally, a significant rearrangement of it has led to it being different from the X.
Taken together, these keep the X and Y from undergoing crossing over in all but tiny portions at
the tips. Hypothesize as to what effect the inability to cross over has done for the X and Y
chromosomes, and, by extension, us..
Evolution Connection Biologists believe that the X and Y chromosomes .pdf
1. Evolution Connection Biologists believe that the X and Y chromosomes were once a fully
homologous pair. Indeed, it is believed that they evolved from an autosomal pair approximately
300 million years ago. Over the years, many genes have disappeared from the Y causing it to
shrink. Additionally, a significant rearrangement of it has led to it being different from the X.
Taken together, these keep the X and Y from undergoing crossing over in all but tiny portions at
the tips. Hypothesize as to what effect the inability to cross over has done for the X and Y
chromosomes, and, by extension, us.
