|Human telomere structure, via Wikimedia Commons, Public Domain image|
The Y chromosome is one of two sex chromosomes and contains over 59 million DNA base pairs, constituting almost 2% of total DNA in human cells. Sex chromosomes determine gender, of course--in normal cases, everyone has a pair of chromosomes, either XX (female) or XY (male). Occasionally there are cases of 48,XXYY (an extra pair of XY), 47XYY (extra Y), and 46,XX (fetus is male despite having female chromosomes due to an abnormal exchange of DNA).
A recent development involving the Y chromosome is the discovery that the most recent common ancestor of the Y chromosome--of which all current male genes are descended from--is thought to have lived 338,000 years ago. This is significantly before the oldest dated human fossils. The Y chromosome can be tracked because of the way it's transmitted, since it doesn't exchange as much genetic material with other chromosomes. Female XX sex chromosomes swap information; male XY chromosomes cannot since X and Y are limited in their compatibility.
I can't believe it's the penultimate day of the A to Z Challenge. Are you looking forward to the end of the month? Will you miss the Challenge?
And what fascinates you the most about human history?
-----The Golden Eagle