fraternal twins

The surprise came when Stanford researchers found a greater number of fraternal twins shared autism than identical twins.

dizygotic A term used for twins derived from two separate fertilized eggs; fraternal twins. Opposite of monozygotic.

Fraternal twins come from two separate eggs. They are no more alike than any other siblings.

In an umber of studies of identical and fraternal twins, researchers have examined the role genetics plays in happiness and unhappiness.

Although fraternal twins share a womb, they are no more genetically alike than any other siblings, Ozonoff says.

The scientists made this conclusion based on the fact that identical twins performed much more similarly than fraternal twins.

Dizygotic (DZ) twins --- Twins produced by two separate ova, separately fertilized. Also called fraternal twins.

Fraternal twins also shared a tendency towards fearfulness but the link was less strong, indicating a genetic component to fearfulness .

Identical twins share identical genetic makeup, while fraternal twins are only as genetically similar as any two siblings.

The study also found that autism rates among both identical and fraternal twins were higher than in the general population.

If identical twins are more similar than fraternal twins, this means genes affect the trait, ie it is heritable.

Identical twins share all their DNA, while fraternal twins share about half, or as much as any brother or sister.

This creates non-identical ( fraternal ) twins - who share on average 50% of their genetic material.

Using data from research on identical and fraternal twins, she concludes that an additional 50 percent is determined by genetics.

To do so, they studied more than 3700 pairs of twins, both identical and fraternal twins, from age seven to ten.

The researchers didn't actually study whether pairs of female identical and fraternal twins had this sexual component.

For this study, they and Christopher Dawes of UCSD used national data that compared more than 1, 000 identical and fraternal twins.

The study found that the likelihood of both twins being affected by autism was higher among identical than fraternal twins.

Identical twins share all of their genes and fraternal twins share only about half.

Jennifer gave birth to fraternal twins on February 22 at New York's North shore University Hospital.

Fraternal twins Jenna (seated on the stone wall) and Barbara were born minutes apart in 1981.

Identical twins share 100 percent of their genes; fraternal twins share 50 percent of their genes.

As expected, the rates among fraternal twins were lower: 31 percent of males and 36 percent of females.

This is what happens in people who share half of their DNA -- fraternal twins.