The platypus genome has been decoded
Scientists have managed to decipher the genetic code of the platypus, which will help to unravel the patterns of mammalian evolution and find their connections with other living creatures – birds and reptiles, the European Laboratory of Molecular Biology said in a statement.
The results of the work, in which British, American and Australian researchers participated, were published on Thursday in the journal Nature.
Platypus and echidna are the last surviving representatives of the oldest mammals, and it is the most distant relative of man among the animals. It is believed that the platypus "diverged" from a common ancestor with humans about 170 million years ago.
This species has many features peculiar only to mammals: for example, platypuses have fur and they feed their young with milk. However, platypuses also have reptilian characteristics – females lay eggs and males produce venom.
Some properties of the platypus, such as the ability to use electricity to detect food under water (electroreception), are inherent only in its closest relatives – echidnas, also belonging to the order of monotremes.
In the process of decoding the platypus genome – determining the sequence of all DNA elements (nucleotides) in its chromosomes – the researchers found that its heterogeneous characteristics correspond to the chaos of platypus genes, similar to the genes of 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 to the days when all mammals laid eggs, feeding their young with milk. It also gives us a solid foundation for future advances in the study of mammalian biology and evolution," says Chris Ponting, the project's lead researcher.
Scientists have studied the platypus genome to find DNA sequences peculiar only to single-passers, as well as those sequences that are known to be associated with the ability to secrete venom, electroreception and milk feeding in other species.
They found that platypus venom is a cocktail of proteins that originally had very different functions. Strikingly, the same proteins were found in the venom of reptiles, although the platypus and venomous snakes evolved independently of each other.
Scientists have also found that the platypus has significantly more sex chromosomes than humans, the structures into which the DNA that determines sex is organized. A platypus has ten sex chromosomes, a human has two. Moreover, in the platypus, the gene sequence that determines sex is more similar to the corresponding genes of birds than to the genes of mammals.
"The platypus looks like a strange mixture of a mammal, a bird and a reptile, and now we know that its genetic code is an equally strange mixture of them all. This is a much bigger mix than anyone could have previously believed," notes one of the project participants, Ewan Birney.
Portal "Eternal youth" www.vechnayamolodost.ru according to the materials of RIA Novosti
08.05.2008