Scientists have cracked the genetic code of the platypus and the results are as weird as the animal itself.

Not only does the little mammal look like it was cobbled together from bits of birds, mammals and reptiles, but so does its genome -- its genetic blueprint.

Jenny Graves, a geneticist with the Australian National University and director of the ARC Centre of Excellence for Kangaroo Genomics, said: "We expected the platypus genome to be a weird amalgam of features and indeed it is. For instance, it has egg yolk proteins (large molecules) like a bird, though not as many as a bird, but all the milk proteins of a cow."

©Rod Scott

Professor Graves is the driving force behind the collaboration of more than 100 scientists from Australia, the US, Britain, Europe, Japan and New Zealand studying the genome of the platypus (Ornithorhyncus anatinus).

It is classified as a mammal because it produces milk and has fur. As it lays eggs, though, it is sub-classified as a monotreme, along with the echidna. The oddball creature split from the lineage that led to modern mammals, birds and reptiles 166 million years ago.

Professor Graves and her colleagues ordered, or sequenced, the building blocks of its genome and compared it with those of people, mice, chickens, dogs and opossums. They found the platypus shared 82 per cent of its genes with those species.

Among the peculiar findings they reported overnight in the journal Nature was that the venom in the spurs of the male platypus is a cocktail of proteins similar to snake venom.

Professor Graves said platypus sex determination was also peculiar. "The platypus does it like a bird," she said. That is, the gene sequences that determine sex are more similar to those in birds than in mammals. The creature has no SRY gene, the gene that makes human males male.

Team member Richard Wilson said another surprise was the discovery of genes for a type of odour receptor that is common in animals such as dogs and rodents that rely on a sense of smell.

Francis Collins, head of the US National Human Genome Research Institute, which funded most of the work, said: "At first glance, the platypus appears as if it was the result of an evolutionary accident but, as weird as this animal looks, its genome ... is priceless for understanding how fundamental mammalian biological processes have evolved."

To view the platypus genome, go here.