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. Girl-boy twins occur when one X egg is fertilized with an X sperm, and a Y sperm fertilizes the other X egg.
Mixed-gender twins are the most common type of fraternals, some 50 percent are boy-girl.
Non-identical (dizygotic) twins happen when 2 separate eggs are fertilised and then implant into the womb (uterus). These non-identical twins are no more alike than any other 2 siblings. Non-identical twins are more common. The babies may be of the same sex or different sexes.
… Identical twins (also called monozygotic twins) result from the fertilization of a single egg by a single sperm, with the fertilized egg then splitting into two. Identical twins share the same genomes and are always of the same sex.
Monoamniotic-monochorionic Twins
This is the rarest type of twin, and it means a riskier pregnancy as the babies can get tangled in their own umbilical cords. If you have monoamniotic-monochorionic twins, your healthcare provider will monitor your pregnancy closely.
Mirror twins, or mirror image twins, is a term used to describe a characteristic of some twins whose features appear asymmetrically—that is, on opposite sides. When these twins are facing each other, it is as if they are looking in a mirror.
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.
In pregnancies with one placenta and two amniotic sacs, you will definitely have identical twins. Additionally, when your babies share a placenta, there is a greater risk for complications, such as twin-to-twin transfusion syndrome.
Identical twins are almost always the same sex, although there are some rare exceptions to this rule. Because identical twins occur when a single fertilized egg splits and forms two embryos, each embryo has the same chromosomes (usually, XX for girls or XY for boys).
The twin gene is carried by the mother, meaning that it is her genes that determine whether someone may have fraternal twins.
Factors that increase the chance of twins include: consuming high amounts of dairy foods, being over the age of 30, and conceiving while breastfeeding. Many fertility drugs including Clomid, Gonal-F, and Follistim also increase the odds of a twin pregnancy.
It's technically possible for two siblings to be as close as 9 or 10 months apart. After your pregnancy comes to an end, you'll start ovulating again before you have your first postpartum period.
The longest interval between the birth of twins is 90 days, in the case of Molly and Benjamin West, dizygotic (fraternal) twins born in Baltimore, Maryland, USA to parents Lesa and David West (all USA) on 1 January and 30 March 1996.
VERDICT: As per World Health Organization, a gap of at least 24 months should be there between your first and second child. By this time, the mother's body gets fully recovered from her first pregnancy as she replenishes the nutrients she lost in her first pregnancy.
Twin reversed arterial perfusion (TRAP) occurs in identical twin pregnancies when one twin has an absent or non-functioning heart and receives all of its blood from the normally functioning and developing "pump twin." The twins are joined by a large blood vessel between their umbilical cords.
The hybrid twin is a simulation model working at the intersection of virtual and digital twins.
It's a common misconception that twins skip a generation in families. There is absolutely no evidence, other than circumstantial, that twins are more likely to occur every other generation.
Identical (i.e., monozygotic, or MZ) twins share 100 percent of their genes, whereas fraternal (i.e., dizygotic, or DZ) twins generally share only 50 percent of their genes.
They come from the same fertilized egg and share the same genetic blueprint. To a standard DNA test, they are indistinguishable. But any forensics expert will tell you that there is at least one surefire way to tell them apart: identical twins do not have matching fingerprints.
ing of fertility. The concept of fertility symbolized by twins corroborated by the study of more than a dozen dreams-is confirmed by mythology. The most obvious meaning suggested by twins is fertility, although it seems to be considered a bad omen.
The risk of preterm labor and premature birth are heightened when there is more than one baby in the womb. 1 Other conditions such as preeclampsia, placental dysfunction, and twin-to-twin transfusion syndrome are more prevalent in twin pregnancy and increase the risk of an early delivery.