Platypus Genome

Genetics Of The Weird Is Still Weird

Here is a NYT article on the Platypus genome.

In their investigation of the platypus genetic blueprint, the scientists found that its genome contains about 18,500 genes, similar to other vertebrates and about two-thirds the size of the human genome. The platypus shares 82 percent of its genes with the human, mouse, dog, opossum and chicken. Some repeated elements in the genome, the scientists noted, hold hints as to the chronology of changes in the platypus.

Of particular interest, the researchers reported, the analysis identified families of genes that link the platypus to reptiles (like those for egg-laying, vision and venom production), as well as to mammals (antibacterial proteins and lactation). The platypus lacks nipples; the young nurse through the abdominal skin.

One surprise was finding genes responsible for sensitive odor receptors. As a primarily aquatic animal, the platypus was already known to rely on electrosensory receptors in its bill to detect faint electric fields emitted by underwater prey. So why the considerable ability to sense odors? The scientists speculate that it may involve sexual communication or the use of water-soluble odorants in navigating and hunting underwater.

Richard K. Wilson, director of the Genome Sequencing Center at Washington University, said that the comparison of the platypus genes to those of other mammals was the beginning of an examination of how “genes have been conserved throughout evolution.”

The project, involving scientists from eight countries, was primarily financed by the National Human Genome Research Institute in the United States. Its director, Francis S. Collins, said, “As weird as this animal looks, its genome sequence is priceless for understanding how mammalian biological processes evolved.”

It's interesting that they share as much with humans as they do. The venom thing, the egg-laying thing, the duck-billed thing make them so strange, and yet they are close as 82% to placental mammals.