Platypus study reveals strange genetic makeup When European settlers first arrived in Australia, reports of a strange animal with a duck's beak were originally dismissed as a practical joke. Later they were cited as proof that God had a sense of humour. The strange creature was the duck-billed platypus. Now, a recent stud... When European settlers first arrived in Australia, reports of a strange animal with a duck's beak were originally dismissed as a practical joke. Later they were cited as proof that God had a sense of humour. The strange creature was the duck-billed platypus. Now, a recent study has mapped the genetic code of the platypus, showing it to be a bizarre mixture of mammal, reptile and bird. The research has also revealed that the platypus has a very complex sexuality. The genome sequence was attained using DNA from a female platypus, nicknamed Glennie. An analysis of the genetic code was made by an international team, which included researchers from the UK's Medical Research Council (MRC) Functional Genomics Unit in Oxford and the European Molecular Biology Laboratory's European Bioinformatics Institute in Cambridge. The study's findings are published in the journal Nature. The platypus is a monotreme, a type of mammal of which there is only one other living example, the echidna or spiny anteater. These are the only mammals capable of electro-reception; using electrical pulses to detect prey. It is believed that the platypus split from a common ancestor shared with humans approximately 170 million years ago. Although the animal has characteristics that only mammals have, such as fur and rearing its young on milk, it also has reptile-like characteristics such as laying eggs and producing venom. The venom is released from a spur on the males' hind legs. The scientists found that these diverse characteristics are matched by a patchwork of genes which resemble those from reptiles, birds and other mammals. 'The platypus genome is extremely important because it is the missing link in our understanding of how we and other mammals first evolved. This is our ticket back in time to when all mammals laid eggs while suckling their young on milk. It also provides an essential background to future advances in understanding mammalian biology and evolution,' explains Dr Chris Ponting, lead researcher with the MRC Functional Genomics Unit at the University of Oxford. The researchers searched the genome for DNA sequences that are unique to the monotremes. They also looked for those genes known to be involved in venom production, electro-reception and milk production in other species. The team found that platypus venom is a cocktail of proteins, which originally had different functions and developed late in the animal's history. The same proteins are also found in reptile venom, despite the two evolving independently. The researchers also discovered that the platypus has 10 sex chromosomes, compared with two in people. In addition, the gene sequences responsible for determining sex are more similar to those of birds than of mammals. 'The platypus looks like such a strange blend of mammalian, bird-like and reptilian features and now we know that the genome is an equally bizarre mix of all of these. It's much more of a mélange than anyone expected,' says Ewan Birney, who headed the team which performed the genome analysis at the European Bioinformatics Institute.
