Unravelling the ‘Plait-ypus’

Displaying reptilian, avian and mammalian features, the revelation of the draft genome of the extraordinary Platypus’ has opened the door to primitive mammalian biological evolution. This insight comes about by comparing the unique divergent characteristics of reptiles and mammals, and exploring how these traits are both present in the most primitive mammal, the Platypus, determining which mammalian genomes have been conserved throughout their 315 million year history. The Platypus, a monotreme from the therian mammal lineage, is on the first branch of the mammalian tree after its divergence from sauropsids (reptiles and birds), which demonstrates why the Platypus maintains some of these traits, even though it shares 82% of their genes with other mammals including human, dog and mouse.

Not only does this genome sequence aid in determining the evolution of the mammalian genome, but it also displays how it functions, by identifying conserved genes and regulatory sequences. There are 18,527 protein-coding genes, similar to mammals, however it has multiple sex chromosomes revealing similarities to bird chromosomes, and unevenly sized chromosomes resembling its reptilian lineage. The revelation of duplicated and deleted genes in the genome compared to derived eutherians and marsupials, identifies certain characteristics unique to the Platypus such as their expanded natural killer complex, independent evolution of venomous spurs, chemoreceptive traits and egg-laying characteristics, which can be addressed in the current difficult conservation efforts. This may be done through an increased understanding into the biologic evolution of mammalian genomes and the history of monotreme biology.

Primary Source

http://www.nature.com/nature/journal/v453/n7192/pdf/nature06936.pdf

Secondary Sources

http://www.nature.com/news/2008/080507/pdf/453138a.pdf

http://www.nsf.gov/news/news_summ.jsp?cntn_id=111521&org=NSF