August 2007 Archives

Slate Magazine has an interesting article on the relationship of genome size and the ability to fly. The genome size of different dinosaur species and the species that eventually evolved from those species were analyzed and the species that evolved with a smaller genome were the species that developed an ability to fly. The article mentions the large genome (all the genetic information found within an individual) of a salamander especially in relationship to a bird (the salamander genome is 90 times bigger). A large genome requires a large nucleus and thus larger cells. Larger cells lead to less transfer of gases in and out of the cells. Species that fly require a high metabolism and smaller cells that allow a much better transfer of gases. Thus a salamander crawls on the ground and a robin flies above it. But why so large a genome in salamanders? No one knows. It is known that most of the DNA found in salamanders is classified as junk DNA as it doesn't code for a protein but what it does or does not do (maybe it was useful to the species in the past but isn't anymore?) is still being discovered. The Animal Genome Size Database collects data on genome sizes and produced the graph above clearly showing that the larger genome of salamanders. As far as rankings are concerned, salamanders are not number one, but do occupy the second and third place with the aquatic salamanders Necturus lewisi and N. punctatus followed by Necturus maculosus and Amphiuma.