Duke scientists map 'silenced genes'
From Yahoo! News:
Remember biology class where you learned that children inherit one copy of a gene from mom and a second from dad? There's a twist: Some of those genes arrive switched off, so there is no backup if the other copy goes bad, making you more vulnerable to disorders from obesity to cancer.
This is an example of gene imprinting, when the expression of an allele depends upon the parent that contributed the allele. This is another example of one of my favorite phenomena, epigenetics. The weird thing is that scientists really have no idea whether this is adaptive. On one hand, it's hard to see how turning off valuable genes that will be inherited by your offspring is adaptive. On the other, this is a common and specialized function of cells, so it's hard to see how imprinting would persist without conferring some sort of advantage. Time will tell...