the Duck-Bill platypus genome has finally been sequenced (something I know most of you have been eagerly waiting for). What turns out to be fascinating is that the platypus exemplifies one of the less publicized forms of evolution: evolution by gene loss.
When scientists sequencing the platypus genome matched up genes from the platypus to the genes from other mammals, a bunch of genes were missing from the duck-billed creature’s DNA. They were genes for protein-cutting enzymes called proteases. A closer looked revealed that these missing genes were for enzymes made only in the stomach. An even closer look revealed that these genes were not absent altogether, just disabled. Virus-like pieces of DNA had been inserted in the middle of these genes, making it impossible for the cells to make proteins from them. The scientists then looked at other genes for proteins that typically get made in the stomach. Some proteins, for example, create the acidic conditions in the stomach. The genes were broken in the platypus too.