News & Politics - Rare Semi-Identical Twins Discovered

migamoo · 03-26-2007, 01:59 PM

Quote:

Rare Semi-Identical Twins Discovered - Yahoo! News

Twins can be identical, fraternal and apparently semi-identical, scientists now report.

Researchers discovered twins who are identical on their mom's side of the equation but share only half their genes from dad.

Here's how it happened: Two sperm cells fertilized one egg—an event assumed to be very rare—then split into two embryos.

"Their similarity is somewhere between identical and fraternal twins," said geneticist Vivienne Souter, of the Banner Good Samaritan Medical Center in Phoenix, Arizona. "It makes me wonder whether the current classification of twins is an oversimplification."

The finding, detailed in the Journal of Human Genetics, was reported today by news@nature.com, the online site of the journal Nature.

Identical twins are created when one fertilized egg splits into two embryos. They share the same placenta and are always of the same sex. Fraternal twins result from two eggs being fertilized at the same time, each by a different sperm. Each has its own placenta, and they can be the same sex or not.

The semi-identical twins only came to the attention of Souter and her colleagues because one had ambiguous genitalia. The child was born a "true hermaphrodite" with both ovarian and testicular tissue. The other twin is a male, anatomically.

The twins are now toddlers, according to the report. They were conceived and born normally and appear to be mentally normal and are growing normally.

I found this to be highly interesting.

S.A.S.H.A. · 03-26-2007, 06:38 PM

I've always feared having twins, and now my fear has only grown more. Single births for me, please!

Sasha

migamoo · 03-26-2007, 10:42 PM

How has it grown?

fetch · 04-07-2007, 04:27 AM

Interesting. I've also read about quads that were a result of two eggs, which both split, causing two sets of identical twins.

Indian Summer · 04-10-2007, 01:18 AM

The quads thing is almost always true, from what I understand. The only exception is some women have two sets of reproductive organs, uterus and all. It's rare but it happens.

I'm an identical twin... I don't know how many of you know that, so yeah. I find it interesting, but it makes sense to me. I just didn't realize the egg could split before it was fertilized.

luke07 · 04-10-2007, 02:53 AM

I agree, this is interesting. I'm glad I don't have any twins.

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