Science Focus (issue 25)

19 usually formed on high volar pads whereas low volar pads produce the arch-type pattern. Intermediateheight volar pads create the loop-type pattern. Then, how do genetic factors come into play? It was illustrated that the geometry of volar pads can be controlled by genes [1]. For example, EVI1, a limb development gene responsible for the outgrowth of distal limbs and digits, was found to express under the volar pads. It was hypothesized to influence fingerprint pattern by controlling the shape and size of the volar pads through its function to promote cell proliferation, as in the distal ends of the developing limbs [4]. This also provides insight into the correlation between fingerprint pattern and limb-related phenotypes [4]. Researchers discovered that individuals with whorl patterns on both pinky fingers often have a longer pinky finger compared to those with no whorl pattern on pinky fingers; the frequency of whorl patterns on the fingers of both hands (except the thumbs) is also associated with longer pinky fingers [4]. Exception: The Family with No fingerprints We have often taken fingerprint technology for personal identification for granted. Fingerprints are a huge part of our identity in modern society, with applications in mobile phones and immigration. Nevertheless, Apu Sarker’s family in Bangladesh has no fingerprints due to a rare genetic mutation in the SMARCAD1 gene, causing Adermatoglyphia or “Delayed Immigration Disease” [5]. Luckily, it does not cause any serious illnesses, but the family encountered difficulties in their everyday lives because fingerprints became mandatory when obtaining driving licenses, sim cards, and passports. As a result, they could not obtain a driving license nor purchase a sim card for their mobile phones. In Apu’s ID card when he was still 10, he was labeled with “NO FINGERPRINT” as the government officials had no idea on how to issue a card without the means for personal identification. With the advent of modern technologies, such as iris scan and facial recognition, let us all hope those who have such genetic conditions would not unintentionally be discriminated against in the near future. Interesting Fact: Do Monozygotic Twins Share the Same Fingerprints? Have you ever wondered whether identical twins share identical fingerprints? Although they are very similar in appearance and contain the same DNA sequence, they have slightly different fingerprints that are significant enough to be captured by the modern recognition software [6]. Aside from the randomness in the fingerprint formation process, small differences in umbilical cord length, womb position, blood pressure, nutritional intake, and the rate of finger growth during the 13th to 19th week can still influence fingerprint formation as a result [6]! This highlights the importance of how environmental factors apart from genetics also play an essential role in determining our fingerprints. Figure 4 Volar pads on the palm during embryonic development are highlighted in light gray.