Wednesday, December 20, 2006

Parthenogenesis in Komodo dragons

Remember the FIRST Hwang paper in Science, wherein what Hwang claimed to be human SCNT was labeled parthenogenesis?

Parthenogenesis is in the news again:

Genetic tests conducted at the University of Liverpool have proved that all four baby dragons born to a female Komodo called Sungai were conceived by parthenogenesis, a form of asexual reproduction that is known to take place in lizards but never documented in this species before.

Parthenogenesis, which is derived from the Greek words for virgin birth, occurs when an egg spontaneously begins dividing as if it were an embryo, without being fertilised by sperm. It is known to have produced live young in about 70 vertebrate species, mostly reptiles and fish, and is thought to be encouraged when females are separated from males.

In humans, females have two X chromosomes and males one X and one Y chromosome. Komodo dragons and other species of the Varanus genus have W and Z chromosomes instead, and dissimilar chromosomes always produce a female.

When parthenogenesis takes place, the egg originally carries just one chromosome, either W or Z, which is duplicated. This means that all offspring are male, and able then to breed with their mothers.

from timesonline


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