Know your finger prints

Fingerprints and physical appearance in general are part of an individual’s phenotype, which arises from the interaction of the individual’s genes and the developmental environment in the uterus. In the case of fingerprints, the genes determine the general characteristics of the patterns that are used for fingerprint classification. As the skin on the fingertip differentiates, it expresses these general characteristics. However, as a surface tissue, it is also in contact with the amniotic fluid in the uterus. The fingertips are also in contact with other parts of the fetus and the uterus, and their position in relation to uterus and the fetal body changes as the fetus moves on its own and in response to positional changes of the mother. Thus the microenvironment of the growing cells on the fingertip is in flux, and is always slightly different from hand to hand and finger to finger. It is this microenvironment that determines the fine detail of the fingerprint structure. While the differences in the microenvironment between fingers are small and subtle, their effect is amplified by the differentiating cells and produces the macroscopic differences that enable the fingerprints of twins to be differentiated.