Fraternal Twins
There's nothing quite as awkward as living in a shadow that is quite literally the same shape as yours - Emma Lord
HWN Suggests
Having fraternal twins is in your genes—and in your hormones
Researchers have long known that women whose families include fraternal twins are more likely to give birth to twins themselves, and they're finally starting to figure out why. After scanning data from nearly 2000 mothers of fraternal twins, scientists from eight countries found two genes that increase a woman's chance of having twins—one that affects hormone levels and another that may alter how ovaries respond to them. The second of these may also have implications for why some women respond better than others to in vitro fertilization.
Articles of Interest
Bringing Up Two at Once
Fraternal twins, however, are particularly competitive and sometimes given to intense jealousy. Their rivalry is intensified because each twin has entirely different poten tials and abilities.
Facts About Fraternal Twins That May Surprise You
Fraternal twins generally are conceived one of two ways – when the mother releases more than one egg during her cycle or when the mother experiences another cycle and releases an egg after she is already pregnant, which can occur up to 24 days after the release of the first egg. For this reason, fraternal twins can be conceived a few weeks apart, though they generally will be born at the same time.
Fraternal Twins: The Hidden Pairs
The media love identical twins, but fraternal twins are also important. Fraternal twins are far more common than identical twins, yet the media focus on the latter. Understandably, their matched appearance makes for great visual effects.
Genetic Variations Help Make Fraternal Twins More Likely
Fraternal twins tend to run in families, and scientists think they've identified genetic variations at play. Understanding that might someday help predict who is more likely to have a risky pregnancy, and might also help treat fertility problems.
Not all twins are identical and that’s been an evolutionary puzzle, until now
When a mother gives birth to twins, the offspring are not always identical or even the same gender. Known as fraternal twins, they represent a longstanding evolutionary puzzle.
The Science of How Women Can Have Twins With 2 Different Fathers
Fraternal twins (50% shared genetics): Fraternal twins result when two separate sperm fertilize two separate eggs. Both babies are a mix of the mother and father, but they don’t share the exact same genetics.
Resources
National Human Genome Research Institute
Fraternal twins (also called dizygotic twins) result from the fertilization of two separate eggs with two different sperm during the same pregnancy. Fraternal twins may not have the same sex or appearance. They share half their genomes, just like any other siblings. In contrast, identical twins (or monozygotic twins) result from the fertilization of a single egg by a single sperm, with the fertilized egg then splitting into two. As a result, identical twins share the same genomes and are always the same sex.
