There are two types of twins – identical (monozygotic) and fraternal (dizygotic).
Dizygotic (DZ) or fraternal twins (also referred to as "non-identical twins", "dissimilar twins", "biovular twins", and, informally in the case of females, "sororal twins") usually occur when two fertilized eggs are implanted in the uterus wall at the same time.
If twins are a boy and a girl, clearly they are fraternal twins, as they do not have the same DNA. A boy has XY chromosomes and a girl has XX chromosomes.
As expected, first-born twins had greater birth weight than second-born twins. With respect to height, first-born twins were slightly taller than second-born twins in childhood.
Identical twins jokingly refer to fraternal twins as “second-class twins.” In French, they are called faux jumeaux, which translates as “fake twins.” A video clip about the Twins Days Festival in Twinsburg jokes that fraternal twins are illegitimate participants in the festival.
Superfetation involves two embryos that form during two separate menstrual cycles. With superfecundation, your body releases two or more eggs during the same menstrual cycle. Each egg is fertilized by sperm, which can be from the same or a different partner or donor. A note from Cleveland Clinic.
There are two types of twins – identical (monozygotic) and fraternal (dizygotic). To form identical twins, one fertilised egg (ovum) splits and develops two babies with exactly the same genetic information.
Monochorionic-monoamniotic twins are identical twins that share both a placenta and an amniotic sac. This is the rarest and highest risk form of twin pregnancies.
It is estimated that 1 in 250 natural pregnancies will naturally result in twins. While twin pregnancies can happen by chance, there are some factors that may increase your odds of having two babies at the same time. Let's learn about twins!
Identical, or monozygotic (MZ), twins have 100 percent of their genes—including those that influence risk for alcoholism—in common, whereas fraternal, or dizygotic (DZ), twins share (on average) only 50 percent of the genes that vary in the population (see figure). Common Environmental Sources.
Homopaternal superfecundation is fertilization of two separate ova from the same father, leading to fraternal twins, while heteropaternal superfecundation is a form of atypical twinning where, genetically, the twins are half siblings – sharing the same mother, but with different fathers.
It is possible for twins to have different fathers in a phenomenon called heteropaternal superfecundation, which occurs when two of a woman's eggs are fertilized by sperm from two different men.
In 99.9% of cases boy/girl twins are non-identical. However, in some extremely rare cases resulting from a genetic mutation, identical twins from an egg and sperm which began as male (XY) can develop into a male / female pair.
Occasionally, two sperm are known to fertilize a single egg; this 'double fertilization' is thought to happen in about 1% of human conceptions. An embryo created this way doesn't usually survive, but a few cases are known to have made it — these children are chimaeras of cells with X and Y chromosomes.
The twin gene is carried by the mother, meaning that it is her genes that determine whether someone may have fraternal twins.
What does Irish twins mean? Irish twins is a slang expression for siblings born less than a year apart from each other. While some people intend it affectionately, it does stereotype Irish culture, making it mildly offensive.
There is no right or wrong answer, it's a personal preference. Some chose to be completely open or tell their twins to give a “smaller” twin leverage if he/she is older. Other choose not to tell so that they don't bicker about the subject or the dominate “older” twin doesn't have more leverage.
Birth Order and Twins
The babies' order of birth is determined by their position in the womb, which can change throughout pregnancy. In some cases, which baby is born first depends on how the mother delivers; the order might be switched if the mother had a Cesarean section rather than vaginal delivery.
Are twins hereditary? Yes, some types of twins are hereditary, meaning that twins run in families. Heredity on the mother's side ups a couple's odds of conceiving fraternal twins. Fraternal twins are two babies from two different eggs that were released from the ovaries simultaneously.
Identical twins do not have identical fingerprints, even though their identical genes give them very similar patterns. 1 The fetus begins developing fingerprint patterns in the early weeks of pregnancy. Small differences in the womb environment conspire to give each twin different, but similar, fingerprints.