With so many twins among us these days, it ' s high time we celebrate some of the most interesting facts about them.
IDENTICAL TWINS
DO NOT HAVE
IDENTICAL
FINGERPRINTS
A photo of actual �ngerprints from identical twins in 1952. You might think that because identical twins supposedly share almost the same DNA, they must also have identical �ngerprints. Well, that ' s not true. Fingerprints are not solely generated based on DNA. When identical twins are conceived, they start out with the same �ngerprints, but during weeks six through 13 of pregnancy, as the babies start to move, they each touch the amniotic sac, and unique ridges and lines are formed on each twin ' s hand that result in different �ngerprints.
Massachusetts has the most twin births of any state in America
At nearly 4.5 for every 100 live births, Massachusetts has the highest rate of twin births. Connecticut and New Jersey follow with 4.2 twins per every 100 births. Researchers hypothesize that more multiple births occur in " af�uent towns outside of Boston " because of a higher concentration of wealthier women who have pursued careers. These women are more likely to attempt to have children at a later age and seek reproductive assistance. The state with the lowest rate of twin births is New Mexico.
Mirror image identical twins have reverse asymmetric features
About 25 percent of identical twins develop directly facing each other, meaning they become exact re�ections of one another. According to About. com, " they may be rightand left-handed, have birthmarks on opposite sides of their body, or have hair whorls that swirl in opposite directions." This occurs when the twins split from one fertilized egg more than a week after conception.
Identical twins do not always have the same genetics
While identical twins derive from one fertilized egg that contains a single set of genetic instructions, also known as a genome, it ' s still possible for identical twins to have serious differences in their genetic makeup. Geneticist Carl Bruder of the University of Alabama at Birmingham closely studied the genomes of 19 sets of adult identical twins and found that in some sets, one twin ' s DNA differed in the number of copies of each gene it had. Normally, every person carries two copies of every gene, one inherited from each parent, but Bruder explains that there are " regions in the genome that deviate from that two-copy rule, [ and ] these regions can carry anywhere from zero to 14 copies of a gene."