Genetics questions

[Anne Shelton]

1) In another newsgroup, the question of eye color came up. How many
genes does it take to determine eye color. I know there's more than
1 because there are  many shades and different eye colors. Some 
people can't get over high school biology: Brown is dominant over
blue.  Some references and quotable sources would help.

2) Second Question: is the X sex chromosome required for viability? A
single X (Turner's Syndrome) is a sterile female but are there any single
Y syndromes (living)? If so, what is it called and what are the syndrome
effects?

3) Third Question:  In the Trisomy combinations of the sex chromosomes,
XXX, XXY, XYY, (YYY?) what are the different effects of these genetic
combinations? (i.e. XYY = aggressive male)

I hope someone with firsthand knowledge out there can provide the
answers to the above questions. Thanks in advance.

Regards,
Anne Shelton