Duck-billed platypus genome sequence...(atypus whose ancestors split from the re...)

Date:5/9/2008

atypus, whose ancestors split from the rest of mammalian lineage some 166 million years ago, with the well-characterized genomes of the human, mouse, dog, opossum and chicken, as well as the draft genome sequence of the green anole lizard. The chicken genome was chosen because it is descended from the ancestral group of egg-laying animals, including extinct reptiles, which passed on much of their DNA to animals like the platypus. Scientists were particularly interested in finding features within the platypus genome that could explain the odd mix of characteristics seen in the platypus, those that were more like reptile and birds and which were like mammals.

The team found that the platypus genome contains about the same number of protein-coding genes as other mammals -- approximately 18,500. The platypus also shares more than 80 percent of its genes with other mammals whose genomes have been sequenced. Next, researchers combed the platypus genome looking for genetic evidence of sequences unique to platypuses, which have been lost from mammalian genomes. Scientists were also eager to find out what characteristics of the platypus were linked at the DNA level to reptiles or mammals.

The mix of reptilian, mammalian and unique characteristics of the platypus genome provides many clues to the function and evolution of all mammalian genomes, said Richard K. Wilson, Ph.D., director of Washington University School of Medicines Genome Sequencing Center and the papers senior author. Now, well be able to pinpoint genes that have been conserved throughout evolution, as well as those that have been lost or gained.

The female platypus lays eggs, a reptilian characteristic, yet also produces milk to nourish its young, which is a mammalian characteristic. Interestingly, the platypus genome harbors both reptilian and mammalian genes associated with fertilization of eggs. However, researchers discovered that, like other mammals, the platypus genome contain
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Contact: Geoff Spencer spencerg@mail.nih.gov 301-402-0911 NIH/National Human Genome Research Institute Source:Eurekalert

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