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Semi-Identical Twins

kamalktk

Antediluvian
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Feb 5, 2011
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So rare doctors have identified only the second ever case.
Semi-identical twins are rare, and doctors say they’ve identified the second case ever

You’ve probably heard of identical and fraternal twins, but a report published Thursday says there’s a third kind – sesquizygous twins or “semi-identical.”

Identical – or monozygotic – twins pop up from a single fertilized egg that eventually splits in two and forms two identical boys or two girls. They share 100% of their DNA.

Fraternal – or dizygotic – twins form from two eggs that have been fertilized by two of the father’s sperm, producing two genetically unique siblings. They share 50% of their DNA.

But “semi-identical” twins are so rare, experts say they have only identified two cases – ever.

Right along that DNA-sharing spectrum, “semi-identical” twins share anywhere from 50% to 100% of their genomes, researchers say.

And they’re extremely, extremely rare. The only other reported case of sesquizygotic twins was reported in the United States in 2007. The recently identified twins from South East Queensland are now 4 years old and healthy.

Details of this second case were published this week in the New England Journal of Medicine. Researchers from the University of New South Wales and the Queensland University of Technology combed through nearly 1,000 cases of twins to confirm their findings. ...

https://www.cnn.com/2019/02/28/health/rare-twins-semi-identical-australia-trnd/index.html

more at link above:

"But in this case, Fisk said, when the egg was fertilized by two sperm, it split the three sets of chromosomes into two separate cell sets, thus forming the twins.
"Some of the cells contain the chromosomes from the first sperm while the remaining cells contain chromosomes from the second sperm, resulting in the twins sharing only a proportion rather than 100% of the same paternal DNA," clinical geneticist Dr. Michael Gabbett, who worked with Fisk, says.
The Australian twins share 89% of their DNA."
 
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Interesting. I used to work with a pair of identical twins - one just minutes younger than the other - but found that after spending a few hours with them it became obvious that they looked really quite different.

But ... I've also known a pair of identicals who were so much like clones that they were able to play tricks, each pretending to be the other, or tricking people unaware of the other twin by doing things that were physically impossible such as apparently teleporting. I certainly never learned to tell the difference.

I know wonder if my identical(ish) colleagues might have belonged to this rare third category of twin.
 
Interesting. I used to work with a pair of identical twins - one just minutes younger than the other - but found that after spending a few hours with them it became obvious that they looked really quite different.

But ... I've also known a pair of identicals who were so much like clones that they were able to play tricks, each pretending to be the other, or tricking people unaware of the other twin by doing things that were physically impossible such as apparently teleporting. I certainly never learned to tell the difference.

I know wonder if my identical(ish) colleagues might have belonged to this rare third category of twin.

I have relatives who are identical twins who as time as gone on have grown to look different and are no longer identical, there were also two twin girls at school who had quite different faces, despite being identical build, having identical hair, similar voices, they now no longer barely look like sisters any more, let alone identical twins. I don't know what causes some twins to be more or less identical than others but it does seem to happen.
 
I'm trying to recall the names of twin little girls in The Simpsons - Terri and Sherri? (I know - could've searchengined it).

They always reminded me of The Shining, which I suspect was entirely deliberate.

On which subject, were Rod 'n' Todd Flanders twins?

A few years back there was a handful of newspaper stories about identical twins who ended up seperated for decades and when reunited turned out to dress very similarly, do almost identical jobs, drive the same car and have selected partners who looked alike and, in one instance, had the same name, and so on.
 
I'm trying to recall the names of twin little girls in The Simpsons - Terri and Sherri? (I know - could've searchengined it).

They always reminded me of The Shining, which I suspect was entirely deliberate.

On which subject, were Rod 'n' Todd Flanders twins?

A few years back there was a handful of newspaper stories about identical twins who ended up seperated for decades and when reunited turned out to dress very similarly, do almost identical jobs, drive the same car and have selected partners who looked alike and, in one instance, had the same name, and so on.

Rod and Todd, they are brothers rather than twins.
 
All sorts of discoveries are being made possibles by advances in genetic analysis technology. Mosaic twins, as above, mosaic (partial) Down syndrome, plus all kinds of rare genetic deletion/microdeletion syndromes which would previously be just written off as being a bit 'backward'.

I'm kind of involved, tangentially, and can recommend this great charity - Unique - Rare Chromosome Disorder Support Group, the reading is fascinating and does give one hope for the future. https://www.rarechromo.org/
 
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