|The Y chromosome. |
Public domain image.
To partly continue yesterday's post about the X chromosome (though reading that one isn't absolutely necessary, in case you're wondering), the Y chromosome, unlike the X chromosome, is associated with males, since males are XY and females are XX. The Y chromosome has around 58 million DNA base pairs (opposed to the X's 155 million), 70-200 genes, and makes up about 2% of all DNA.
95% of the Y chromosome is male-specific, although sections called the pseudoautosomal regions have identical counterparts on the X chromosome. Because of this, only pseudoautosomal regions can exchange places in a process called recombination (which occurs between all of the two X chromosomes in females) and male offspring possess an almost identical copy of their father's Y chromosome.
Conditions that can result from changes in the Y chromosome include 48,XXYY syndrome (where there is both an extra X and an extra Y chromosome in males) and 47,XYY syndrome (where there is the normal one X chromosome, but two Y chromosomes).
|A graphic example of 47,XYY syndrome, with a male on the left |
and female on the right, by Silver Spoon and Lucas Zienius,
However, this is theory has been rather debunked by the finding that no Y chromosome genes have been lost for six million years, and that the Y chromosome evolves rapidly. So, it seems half of the human race is genetically safe. (The chances that humanity will survive for another six million years might be far off, anyway.)
I hope I've made this part of chromosomal biology interesting for you all. Though if not, I hope you'll come back on Monday anyway in which I address a topic that's easier and allows for some great (in my opinion, at least) photographs. ;)
And since it's the second-to-last day of the Challenge: Are you looking forward to slowing down on the blogging in May, or will you just miss it? I'm a bit of both . . .
-----The Golden Eagle