<i>She says that two species of spiny rats in Japan have lost the mammalian Y chromosome completely, shifting many genes to other chromosomes.</i><p>That's interesting! Let's ask the google:<p><i>Although they have no Y chromosome, this species still has males and females. In the opinion of Asato Kuroiwa, an associate professor at Hokkaido University, "A new gene formed within an autosome, replaced SRY and became the switch that determines gender."</i> [0]<p>[0] <a href="http://ajw.asahi.com/article/behind_news/social_affairs/AJ201208230009" rel="nofollow">http://ajw.asahi.com/article/behind_news/social_affairs/AJ20...</a>
Which is more detrimental to the survival of a certain gene, losing vital data or gaining useless data.<p>Some genome sizes, the marbled lungfish carries a lot of weight in its cellular nuclei.<p>ftp://www.fourmilab.ch/pub/goldberg/sizes.html