First Decoded Marsupial Genome Reveals "Junk DNA" Surprise

Marsupials are the closest living relatives of placental mammals. The two groups split from a common ancestor about 180 million years ago.

Scientists were able to pinpoint the genetic elements that are present in placental mammals but missing from marsupials to learn more about what makes the two groups different.

The researchers were surprised to find that placental and marsupial mammals have largely the same set of genes for making proteins. Instead, much of the difference lies in the controls that turn genes on and off.