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Monozygotic twins can develop differently, due to different genes being activated. More unusual are "semi-identical twins". These "half-identical twins" are hypothesized to occur when an unfertilized egg cleaves into two identical attached ova and which are viable for fertilization.


Fraternal twins are “dizygotic,” meaning that they developed from two different eggs fertilized by two different sperm cells, while identical twins are “monozygotic ” i.e., they developed from a single fertilized egg that split. The likelihood of identical twins is the same around the world — about 3 in 1,000, while the incidence of ...


You probably want to know as early as possible if your twins are identical. We explain how and when you'll find out and the effect a shared placenta can have on pregnancy. - BabyCentre UK.


Learn everything you wanted to know about identical (monozygotic) twins, from conception to birth to parenting advice.


Identical twins (monozygotic) occur when a single egg, fertilized by a single sperm, splits into two identical halves. Two separate babies with identical DNA are formed. Identical twins are always the same sex and blood type. They almost always share the same placenta but may also have two separate placentas. Depending ...


They have the same piercing eyes. The same color hair. One may be shy, while the other loves meeting new people. Discovering why identical twins differ— despite having the same DNA—could reveal a great deal about all of us.


Because identical twins develop from a single fertilized egg, they have the same genome. So any differences between twins are due to their environments, not genetics. Recent studies have shown that many environmentally induced differences are reflected in the epigenome.


Identical (one-egg) twins and fraternal (two-egg) twins both receive nourishment that passes from the mother's blood through the placenta and into the fetal blood vessels in the umbilical cord. In about 70 percent of one-egg twins there is only one chorion and one placenta. Each of the two-egg twins has a chorion and, ...


Mar 24, 2014 ... About 25 percent of identical twins develop directly facing each other, meaning they become exact reflections of one another. According to About.com, “they may be right- and left-handed, have birthmarks on opposite sides of their body, or have hair whorls that swirl in opposite directions.” This occurs when ...