Sunday, October 29, 2006

Sex Beyond X and Y

You're feeling pretty good about chromosomes, and you understand that an XX genotype in humans is female, and XY is male.
But honeybees are much more creative. First, honeybee males are haploid - hatching from unfertilized eggs laid by the queen. Diploid eggs hatch into females, so females get chromosomes from both a mother and a father.
An added wrinkle is a gene called csd (complementary sex determining) gene. This gene has many different alleles. As long as the queen and the father have different csd alleles, the diploid egg is heterozygous for csd, and the egg develops into a normal female.
But beekeepers like to inbreed bees to improve desireable traits. And if the queen and father bee have the same allele of csd and both give these to the egg, the diploid egg is homozygous for csd, MALE, and sterile. The workers eat the egg before it develops! So in bees, it's best to date someone very different from you...

1 comment:

Anonymous said...

It's interesting that male honeybees have half as many chromosomes as female honeybees. Before, I thought that only happens with certain plants. The section about balancing selection was also very interesting.