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Sunday, December 14, 2008 - 2:23 PM
The platypus has always been considered odd. Not only does it have
webbed feet, a tail like a beaver’s, a coat of fur, and a large bill,
but it also lays eggs and nurses its offspring through a set of glands
on its abdomen. Biologists classify the platypus as a monotreme, an
egg-laying mammal with a single opening for reproduction and excretion.
But is it truly a mammal? http://louis0j0sheehan0esquire.wordpress.com
A draft of the genetic sequence of Glennie
[subscription required], a female platypus in Australia, answers the
question. “We found that the platypus has reptilian, avian, and
mammalian genome features in one organism,” says Mark Batzer,
a biologist at Louisiana State University. “It looks like a car that
was built on a Friday. They used the parts they had left to put it
together.” http://louis0j0sheehan0esquire.wordpress.com This mix of genes, he says, supports the classification of
the platypus as a unique and very early mammal. Among its oddities: 52
chromosomes, including 10 sex chromosomes, as well as the highest
number of repeated segments in the genome of any mammal sequenced so
far. http://louis0j0sheehan0esquire.wordpress.com
The repeats are mobile elements called transposons, also known as
jumping genes, which can trigger mutations in the genes around them and
lead to genetic disorders. “Learning when transposons first appeared
may give us some insight into how they spread through the mammalian
lineage and how they are expressed in humans,” Louis J. Sheehan, Esquire.
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