Identical Twins Don’t Have Identical Fingerprints, Even from Birth

Today I found out that no two people in this world have identical fingerprints, not even identical twins.
You would expect identical twins to have the same fingerprints as they are monozygotic, which means that they develop when a single fertilized egg splits in two, leading to two embryos. As they both came from the combination of the same egg and sperm, these twins have virtually indistinguishable DNA.

So why aren’t their fingerprints identical from birth? Fingerprints are not entirely a genetic characteristic. They are a part of a ‘phenotype’ which means they are determined by the interaction of an individual’s genes and the intrauterine environment (differing hormonal levels, nutrition, blood pressure, position in the womb and the growth rate of the fingers at the end of the first trimester).
Minor differences in fingerprints arise from random local events during fetal development. The genes determine the general characteristics of the patterns of fingerprints. However, inside the uterus, finger tissue comes in contact with the amniotic fluid, other parts of the fetus and the uterus. Some experts point out, for example, that touching amniotic fluid during weeks 6-13 of pregnancy significantly changes the patterns of fetus’s fingerprints.
Overall, identical twins’  fingerprints tend to be similar, but there always will be subtle differences making even their fingerprints unique.
Bonus Facts:
  • Before modern genetic testing became common, the similarity of twins’ fingerprints was used to determine whether they were identical or fraternal.
  • The odds of having identical twins is about 3 in 1,000, whereas the birthrate for all twins is about 32.2 in 1,000 and there is no known hereditary trait that influences a predisposition to having identical twins. Birth rates for identical twins are fairly consistent and are the virtually the same regardless of race, geography or maternal age.
  • Identical twins lose some fundamental similarities as they grow older. This will reflect in their looks, behavior and diseases they are prone to. The reason for these differences as they grow are changes in the epigenome, which refers to chemical modifications in genes that don’t directly affect a gene’s DNA but result in changes in gene expression. All people build up these mutations over time.  These epigenetic affects may be caused by exposure to chemicals, physical activity levels, aging, dietary habits and other environmental factors. That is why in middle and old age identical twins tend to look more like non-identical twins.
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