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All of the new cells that come from the one with the mistake will have that same mistake. One consequence is that if it happens early, the baby will have more cells carrying that mistake. Think about it like one of those medieval monks patiently copying manuscripts in a monastery somewhere in medieval Europe.
Imagine he makes a mistake during copying and the original manuscript is destroyed. Now every new manuscript contains his mistake. For the English twins, one may have developed a mutation in a gene that affects skin and eye color. Most likely it would be in the lighter child as it is easier to break something than to fix it.
And often traits like blue eyes are the result of a gene not working quite right. Another possibility has to do with how cells read their DNA. Imagine Louis C. Even though they all have the exact same lines to read, odds are there will be real differences in how they say them. Here's how it might work: Near the genes there little chemical markers that can, for example, tell the cell how often to read a gene.
That means she would make less pigment and so have fair skin and blue eyes. Or her sister might have marks on her DNA telling her cells to read her skin and eye color genes much more often. This would explain her brown eyes and cafe au lait skin. What is fascinating about these epigenetic marks is that they're reversible. If the girls' differences are the result of a mutation in the DNA itself, they'll probably go through life as different-looking identical twins.
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. They can pass it along to their daughters too, increasing their daughters' chances of having fraternal twins. If there are fraternal twins on both the mother's and father's sides, your odds for twins goes up even higher. However, having the gene for hyperovulation does not increase a man's chances of fathering fraternal twins.
If a man carries the gene, 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. As medical technology made fertility-enhancing treatments more accessible, the twin birth rate has skyrocketed. Interestingly, while IVF usually results in fraternal twins due to the transfer of multiple embryos at the same time , some instances of monozygotic twinning can also occur.
Because fraternal twins form from separate eggs and sperm, this can lead to some uncommon circumstances in which the twins have different gestational ages or even different fathers.
Sometimes hyperovulation happens a few days apart. After one egg is fertilized and begins to travel to the uterus for implantation, another egg is fertilized by sperm from a later incident of sexual intercourse. The result is fraternal twins who are conceived a few days apart. This is known as superfetation. 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 called superfecundation. During pregnancy, the placenta provides vital sustenance to the baby. 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. Because they have their own placentas, fraternal twins are not at risk for some of the conditions that affect monozygotic twins, such as twin-to-twin transfusion syndrome TTTS or monoamniotic twins.
Each person receives half of their DNA from their mother's egg and the other half from their father's sperm, and so any two offspring will have some overlapping qualities.
Monozygotic twins share the same genetic makeup, or genotype although their DNA is not necessarily identical. This shared DNA is what makes them often have remarkably similar appearances and characteristics.
Unlike monozygotic twins, fraternal twins may look nothing alike, including having different:. Or, they may indeed be so similar that they are assumed to be identical, just as some siblings would be remarkably indistinguishable if they were the same age.
Twins and multiples are also shaped by their environment after they are born. Some similarities are enhanced because they are raised in the same home, share the same experiences, and are educated in the same schools at the same time.
Because fraternal twins originate from separate conceptions, they can both be boys, both girls, or one of each just like a singleton baby.
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 pair of siblings.
Monozygotic twins, on the other hand, are always the same gender, either two girls or two boys. Twins are affected by your health and habits during pregnancy. Fraternal twins share increased or decreased health risks due to sharing the pregnancy environment. While it's not possible to completely eliminate the risks that come with having fraternal twins, you can take some healthy steps to reduce those risks, including:. Your fraternal twins will share many things throughout their lives after starting out in the womb together.
Enjoy their similarities and differences as they grow. With these facts, you'll be able to tell them how they truly are unique. Get diet and wellness tips to help your kids stay healthy and happy.
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