Thanks EveningStar.
Posted on 02/28/2019 4:04:42 PM PST by EveningStar
Boy and girl, now four, are only the second case of ‘sesquizygotic’ twins recorded
A pair of twins have stunned researchers after it emerged that they are neither identical nor fraternal – but something in between.
The team say the boy and girl, now four years old, are the second case of semi-identical twins ever recorded, and the first to be spotted while the mother was pregnant.
The situation was a surprise to the researchers. An ultrasound of the 28-year old mother at six weeks suggested the twins were identical – with signs including a shared placenta. But it soon became clear all was not as it seemed.
(Excerpt) Read more at theguardian.com ...
“By what mechanism did the two absolutely identical maternal haploids come about?”
That is a separate issue than what I addressed: that “an unfertized human egg could split into two”.
Think about why an unfertilized egg can’t split in to two.
If you read the article then your problem is comprehending the information?
(M.Sc. in Reproductive Physiology, in case you wondered).
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Yay...some useful expertise. In this situation, can you explain how two identical maternal haploids arose - I’m assuming from what originally was a single haploid. I asked another poster who seemed that he/she might have some expertise but that poster preferred to play “cute” instead of answering.
Thanks.
Perhaps it was the freemartin issue, I was reading about dairy farming and they want heifers!
Actually, from the article itself, the ovum actually split three ways. The problem with polyspermy is that you get a polyploid situation in the ovum, which has to be evened out during the division cycles, or the resultant daughter cells quickly become non-viable (you can see polyploidy in some plants, which can adapt to tetraploid, and hexaploid situations, but animal cells generally cannot). What happened was that the fertilised ovum split into two daughter cells, each with maternal haploid chromosomes matched up to paternal haploid, as is normal, although the paternal chromosomes themselves were a mix n’ match from each of the two sperm. Still The two normal maternal haploid (from the first mitosis event) matched up to the normal compliment of paternal haploid formed paternal chromosomal chimeras, but still, everything was hunky-dory. There was also an extra mitotic event, where the two ‘odd’ sets of paternal haploid chromosomes were forced to match with each other, and this third cell quickly became non-viable.
Best I can answer it, and still keep it in reasonably layman’s terms. Not sure if that helps.
Non quite there are modi and momo identical twins. Modi is common, momo is very high risk sadly
Quadrotriticale.
(Sorry. Couldn’t resist.)
Thanks EveningStar.
As usual, I forgot to ping you. Sorry. :(
Look up ‘freemartin’. Somewhat common in cattle; now, it seems to also (very rarely) occur in humans, too.
:^) No problemo.
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