How does parthenogenesis work?

Question

I have always been intrigued by the "virgin birth" of unisexual Cnemidophorus species (a whip tail lizard from the American southwest), and of two geckos, Lepidodactylus lugubris and Hemidactylus frenatus.

Recently, I have read news reports of Komodo Dragons being parthenogenetic as well.

The offspring are not genetic clones of their mothers, so how does the genetic diversity occur. Is there a recombination of the chromosomes during meiosis?

Please give me some citations that clearly define this. Thanks.

Answer 1

For one thing, Komodo Dragon chromosomes don't work like humans.  The female has the equivalent of X and Y.  And the males have two copies of X.  So the female gives birth to males by making a copy of her X to give the child two X's.  There is no recombination, and the child is not a clone.

The child can grow up and mate with the mother.  You could call that recombination, but the only new information is mutation, so not much happens.

There is some speculation that parthenogenesis can happen in humans.  If it does, the child can only be a girl.  So this does not explain the birth of Jesus, for example.

Answer 2

Lots of citations and links.....

Answer 3

During oogenesis, the egg splits off from a polar body, giving one the vast majority of the cytoplasm.  This then happens again giving 1 egg and 3 (or 2, the first one might not divide) polar bodies.

One of these polar bodies can refuse (or never actually leave) resulting in a diploid zygote.  This is not a clone due to recombination.

Birds and some reptiles use the ZW s*x determining system (inverse of XY) so the female can produce both a male or a female offspring (in birds it is almost always a male).

Mammals are different.  Besides the obvious problem of only producing females, for proper development information from the sperm is required.

You can chemically induce a parthogen in mammals, however it never develops normally since genetic imprinting is required from the sperm.

In other words, it can't happen in the wild in mammals.