The Science Behind Unique Fingerprints

I am loving the Infection, Immunity and Forensics topic that we are currently covering in Year 2 of A-Level Biology. The specification briefly talks about conventional methods of identifying a body, one of which is the use of fingerprints. This method is dependent upon the fact that all fingerprints are unique to an individual and never change throughout one’s lifetime. The global population stands at just under 7.6 billion people and the chance of your fingerprint being identical to someone else’s is 1 in 64 billion! So, what processes occur that mean every single fingerprint is different? How do we get our fingerprints?

Fingerprints are small ridges caused by folds in the epidermis of the skin; these ridges vary in length and width and can branch or join together to form distinctive patterns. They are even more unique than DNA – although identical twins mostly share the same DNA, they never have the same fingerprints. Each ridge contains pores that are attached to sweat glands under the skin. It’s because of this sweat that you leave finger marks on pretty much everything you touch. 

Unique fingerprints are the result multifactorial inheritance – i.e. affected by both your genes and the environment. The ridges on the tips of your fingers are frictional, and although small, they actually stick up above the rest of the skin. These friction ridges grow in different designs, as mentioned above, and if your parents have a certain pattern, you are likely to have it too; genes give the basic design of the finger ridge pattern, almost like laying fingerprint foundations. These genes also dictate how and when the skin grows. As a fetus develops in the womb, the dermis and epidermis of the skin grow together with friction ridges appearing where the two layers meet, and this is guided by genes. Since growth is entirely natural, and therefore not uniform, the layers grow at different speeds; when one layer grows faster than the other, it stretches and pulls cells in the other layer. In addition, a fetus’ fingers can rub against the inside of the womb. These tiny forces move the skin as it grows, with the cumulative effect being control over that direction of growing ridges which forms the unique fingerprint. Since everyone’s skin grows in slightly different environments, it is highly unlikely that your fingerprint will ever be identical to someone else’s.

Sources:

·       SNAB A2 Biology textbook

·       https://askdruniverse.wsu.edu/2020/02/07/people-different-fingerprints/

·       https://science.howstuffworks.com/fingerprinting1.htm