AP PSYCHOLOGY

Detailed explanation-1: -Even though researchers haven’t pinpointed the cause, some people are at an increased likelihood of having twins. According to The American Society for Reproductive Medicine, women who are fraternal twins have a 1 in 60 chance of having twins, and men who are fraternal twins have a 1 in 125 chance of fathering twins.

Detailed explanation-2: -Even identical twins, who share all their genes, differ in their vulnerability. The study found only a 45 percent concordance rate for identical male pairs. This means that of all pairs where one twin has Alzheimer’s, 55 percent of the healthy twins either will never get the disease or will develop it later in life.

Detailed explanation-3: -Identical twins share the same genomes and are always of the same sex. In contrast, fraternal (dizygotic) twins result from the fertilization of two separate eggs with two different sperm during the same pregnancy. They share half of their genomes, just like any other siblings.

Detailed explanation-4: -Diseases that tend to strike identical twin pairs at a higher rate than fraternal twins or siblings are probably influenced by genetics, Lakhani said. Diseases that happen in sibling pairs, regardless of whether they are twins, tend to be strongly influenced by environmental factors.