Biometric Fingerprint Machine
The heat is unbearable; I feel as though I’m being cooked alive. I’m waiting in the immigration line at Dar es Salaam airport in Tanzania: the aggravating buzzing coming from the innumerable number of flies only adds to the groans of the people waiting in the queue. While I wait (impatiently!) with my clothes practically glued to my skin with sweat, I can see why this process is taking so long. Everyone is having their fingerprints scanned on this fluorescent green square. Each finger is done waiting for the lights to change from red to orange until they are finally green. Until this point they were just those weird things that went wrinkly in the bath!
While I waited in the stifling heat mindlessly letting my imagination go wild- I thought the unthinkable; what if you didn’t have fingerprints? What would they do then?! Actually where do those funny little lines that governments, CSI and spy novelists deem so important, even come from? What do they mean? Are they just a built-in barcode used to separate us from the next person? Can they tell us anything about ourselves? This made me realise that despite the on pour of sweat and irritation, I really should give more thought to these near invisible marks on my body that at this very point are all individually keeping me from the cool air-conditioned baggage reclaim area…
Scanning electron micrograph of the ventral surfaces of the hand (A) and the foot (B) of a human embryo as the second month. Volar pads are prominent near the tips of the digits.
Forces applied to the basal layer.
Our journey of discovery begins in the womb; a remarkable underwater cavern especially constructed for its miniature inhabitant(s). This protective marine bubble creates the perfect environment for a developing foetus. At only around 2 inches long and within the first 6 to 7 weeks the fingers break away from each other and then a wax-like pad forms on the fingertips. These pads are called volar pads and the fingerprints begin to develop once these disappear at the 10th week. The apical skin below contains an epidermal layer, basal layer and a dermis layer as shown in the image.
Michael Kücken and his colleagues noticed that the basal layer grew much faster than the layers on either side of it, causing them to crumple and form ridges. But, because of the way mechanical forces work and the way this layer grows in relation to the others, the lines are random and so many different variations of the lines can be formed. Other factors cause the lines to change shape and direction; forces from fingernail beds and formation of the knuckles. From the 13th week you can see that the basal layer has buckled under the pressure and ridges are being formed, and by the 16th week the patterns formed are permanent. However, it doesn’t quite stop there; cell division within these patterns continues to happen and so they actually become deeper and more defined!
Each fingerprint pattern or more scientifically put; dermatoglyph, are unique! They are epigenetic meaning that the genes provided by each parent contribute to the patterns and ridges produced in addition to the environment impacting on its DNA expression. What this means is that while a bit of the pattern is down to your genetic make-up, other factors such as amniotic flow and density, your mother’s hormone levels and blood pressure during pregnancy and your position in the womb, can all change the expression of your genes to produce different patterns. In fact, so much so that disrupting the amniotic fluid in any way during weeks 6-13, can noticeably change the pattern of the fingerprints! What this means that everything we do and that we are exposed to in the womb defines what that black smudge in our passports is going to look like!
As the cells on the finger pads begin to differentiate, the fluid around each fingertip changes; constantly creating a slightly different microenvironment for each finger. Babies can be pretty active too and by changing their position in the womb, and touching other parts of their body as well as the uterus, they further add to the finer changes that can be seen between each dermatoglyph. All of this provides a really good explanation of why identical twins (who have the exact same DNA) have different fingerprints. To further the importance of this, fingerprints are so unique that they are considered a legitimate piece of evidence in courts worldwide; being able to distinguish between two identical twins is essential in determining which twin is guilty.
Adermatoglyphia
Now back to the question that started this journey of discovery; what if you didn’t have fingerprints? Well it turns out some people don’t. These individuals have a genetic mutation on the SMARCAD1 gene region which causes the process of dermatoglyph development to be skipped during foetal development! It is autosomal dominant condition, which means that you only need one of your parents to have this gene mutation for it to be passed on to you. The condition is called adermatoglyphia, and unsurprisingly it used to be called immigration delay disease and after experiencing the fingerprint scanner, I can now fully appreciate why!
Further Reading:
The link between fingerprints and diabetes? Find out here http://ije.oxfordjournals.org/content/38/1/101.full
Thanks to:
Kücken, M., & Newell, A. C. (2005). Fingerprint formation. Journal of theoretical biology, 235(1), 71–83. doi:10.1016/j.jtbi.2004.12.020 at http://www.ncbi.nlm.nih.gov/pubmed/15833314
Garzón-Alvarado, D. A., & Ramírez Martinez, A. M. (2011). A biochemical hypothesis on the formation of fingerprints using a turing patterns approach. Theoretical biology & medical modelling, 8(1), 24. doi:10.1186/1742-4682-8-24 at http://www.tbiomed.com/content/8/1/24
ReproMed Diaries 