Although
it’s long been known that fraternal twins run in families, researchers say
they’ve just pinpointed two genes that seem to be associated with having such
twins.
Fraternal twins occur when two separate
eggs are fertilized with two separate sperm, creating two genetically unique
children in the same pregnancy.
One gene variant — called FSHB — increased
the odds of having twins by 18 percent, according to the study. FSHB is
associated with higher levels of follicle-stimulating hormone (FSH), which
increases the likelihood that a woman’s ovaries will release multiple eggs at
the same time. And, multiple eggs boost the odds that more than one egg will
get fertilized at the same time, the researchers explained.
The second genetic variant — SMAD3 — upped
the odds of fraternal twins by 9 percent, the study found. SMAD3 likely plays a
role in how the ovaries respond to FSH, the researchers said.
Women with both variants were 29 percent
more likely to have twins, the study showed.
The study was published April 28 in the American Journal of Human Genetics.
“There’s an enormous interest in twins,
and in why some women have twins while others don’t,” study author Dorret
Boomsma, said in a journal news release. She’s a biological psychologist at
Vrije Universiteit in Amsterdam, in the Netherlands.
“The question is very simple, and our
research shows for the first time that we can identify genetic variants that
contribute to this likelihood,” Boomsma added.
The findings stem from genetic analyses of
more than 5,500 women from Europe, the United States and Australia who
conceived fraternal twins with and without fertility treatment. The study also
included genetic information on more than 300,000 women who didn’t have twins.
According to the researchers, the results
are important for infertility research. FSH is injected to stimulate the
ovaries and obtain eggs for in-vitro fertilization, but some women’s ovaries
over-respond to the hormone, the study authors explained.
The
researchers said they plan to develop a genetic test to identify women at risk
for this problem.
Nice reading! Fraternal twins have their own little space in their mother’s uterus and are surrounded by their own amniotic membranes. They do not share a placenta and each has their own. Unlike identical twins, fraternal twins can be different genders or the same. I've read somewhere that very rarely, a mother who is already pregnant releases another egg in the same month which is then fertilised by a separate sperm. This is a phenomenon known as superfetation. But this can only happen a few weeks after the first baby has been conceived. This may account for the reason why at birth, one fraternal twin can appear much larger and more mature than the other one.It is also possible for a woman to conceive fraternal twins with two different biological fathers!! Mom nature is tricky lol
ReplyDeleteAt birth it can be very difficult to tell fraternal twins apart. Sometimes it’s not until there are two placentas identified that that it is clear that the twins are fraternal. But remember, identical twins can also have two placentas, depending on the stage of cell multiplication that they divided. But as they mature, each fraternal twin develops their own unique appearance and often turns out to be no more similar to look at than any other siblings in the same family. Alternately, fraternal twins can appear completely different to each other right from birth, with different hair colouring, facial features, sizes and birth weights. If they are very alike, even parents can have difficulty telling them apart.
Just love the whole idea. We all know that fraternal twins each come from their own egg and sperm. But there are so many surprising facts about them! After doing some research on the topis I would like to add ~
ReplyDeleteBecause fraternal twins originate from separate conceptions, they can be boys, girls, or one of each. Chromosomes from the father's sperm determine gender: XX for a girl and XY for a boy. As a result, the chances of fraternal twins resulting in boys, girls, or a combination are the same as for any other babies. Just like any brothers and sisters, fraternal twins will share about 50 percent of their DNA. Each person receives half of their DNA from Mom's egg and the other half from Dad's sperm, and so any two offspring will have some overlapping qualities. But they aren't the perfect genetic match that identical twins are for example. Fraternal twins, on the other hand, are as alike as any two siblings. They may look very different. They can have different hair color, eye color, stature, and personalities. Or, they may indeed be so similar that they are assumed to be identical, just as some siblings would be remarkably indistinguishable, if only they were the same age. One more interesting thing to share. In a multiple pregnancy with fraternal twins, a placenta develops for each baby. Sometimes, however, the two placentas fuse together and appear to be one single placenta. Women who hyperovulate are more likely to have fraternal twins. A tendency towards hyperovulation can be a genetic trait. In this way, fraternal twinning can be hereditary. A woman who has the gene for hyperovulation can pass it down to her daughter. Then, the daughter's chances of having twins are increased)) Because men carry both X (female) and Y (male) chromosomes, they can also hold the trait for hyperovulation and pass it along to their daughters, increasing their daughter's chances of having fraternal twins.
However, having the gene for hyperovulation does not increase a man's chances of fathering fraternal twins. A man carries the gene, but it doesn't change the ovulation pattern of the mother of his children. She has her own genes governing her ovulation. Instead, it would be his daughter who inherits it through his genes. That is why twins are sometimes assumed to "skip a generation."There have even been instances of fraternal twins with different fathers. This occurs when a woman releases multiple eggs and has sexual relations with more than one partner. If an egg is fertilized by sperm from one man, and then another egg is fertilized by sperm from another man, the result is fraternal twins with different fathers. This phenomenon is termed superfecundation. Have no words! Nature is just awesome!!!
Truly amazing thing with fraternal twins at all! Fraternal twins are conceived when the mother hyperovulates. It seems she ovulates more than one eggs during her cycle. Then different sperms fertilize these different eggs. This phenomenon can occur only up to 24 days after the first egg is released. In such a case, the twins would have been conceived at different dates but will be delivered on the same day (Despite the developmental differences. Research indicates that there is a higher probability of giving birth to twins if parents have undergone fertility treatments, or if the mother is over 35 years of age. Fraternal twins share only 50% of their genetic makeup. They can, therefore, look as similar as identical twins or as different as ordinary siblings. Most twins are believed to share a special bond. It connects them more deeply than normal siblings. They may often have an almost telepathic sense of any harm that their twin may be experiencing. While most people believe this to be true for identical twins, it is also true at some level for fraternal twins. Really interesting to know. Thank you for sharing this very piece of info.
ReplyDeleteI just wanted to share. Our Dr at Biotexcom repro center kindly explained us that chances for having twins don’t increase because of undergoing assisted reproductive treatments. Monozygotic twin pregnancy occurs when an embryo splits into twins at some time very early. This results in two identical twins which are genetically identical. As for non-identical twins, they develop in a different way. They are the result of two different eggs that have been fertilized by the same sperm cycle. which result in genetically different embryos. This all is so mush interesting! We've been happy to have professionals by side who'll kindly explain everything we get interested in. Special thanks!
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