I realize you may be shocked. Yes, even identical twins do not have the same fingerprint so how can we inherit fingerprints. The answer is simple. We inherit some parts of our fingerprints from our parents.
Fingerprints are the unique patterns, made by friction ridges (raised) and furrows (recessed), which appear on the pads of the fingers and thumbs. These ridges are called frictional ridges skin. They appear on the skin, palms, and even toes to allow us to hold things firmly and prevent slippage. Even though we all have unique fingerprints, our fingerprints are similar.
The pattern, spacing, size and shape of our fingerprint is determined by genetics. Everyone has one of these 3 types or patterns of fingerprint: arch, loop and whorl. As humans, we obtain half of our chromosomes from our parents hinting that we are likely to share the same pattern and spacing with our parents. They transfer these characteristics to us during development.
Regardless, fingerprints appear unique to every individual because apart from genetics, the environment that houses the fetus during development affects the finer details. If you are to look closely, you will realize that there are small variations between the fingerprints such as dots, forks, openings, and so on.
Thus, even identical twins who share the same genes from their parents will develop in different parts of the womb ultimately creating a unique fingerprint. Environmental factors in the womb that enhance unique features include the thickness of the amniotic fluid, the position of the fetus and what the fetus touches while in the womb.
Formation of fingerprint
Parents transfer all the genetic material a child needs to grow during fertilization yet offspring end up with unique fingerprints. This is how it happens:
Two main events occur that affect the specificity of the fingerprint during week 10 to week 15. At week 7, fetuses begin to develop smooth volar pads which are raised pads on the fingers, palms and feet. This happens due to the swelling of mesenchymal tissue which is a precursor of blood vessels and connective tissues.
At week 10, the swelling which caused the smooth volar pads to form stops but the hand and feet continue to grow. As a result, the volar pads shrink or are reabsorbed back into the hand over the next few weeks. At this stage, the ridges that form the fingerprint begin to appear on the skin of the volar pads. They are called the primary ridges because they appear first.
The type of fingerprint pattern, its arrangement and spacing that forms depends on how much volar pads has been absorbed when the early ridges begin to form.
If the primary ridges begin to form when the volar pads are pronounced or very present, then a whorl pattern will form. (high volar pad)
If the primary ridges begin to form when the volar pads are partially absorbed, then a loop pattern will form. (intermediate volar pad)
If the primary ridges begin to form when the volar pads are almost gone or entirely absorbed, then an arch pattern forms. (low volar pad).
In summary, the timing of the volar pad regression and primary ridge appearance is genetically linked. The pattern type which is influenced by genetic timing is inherited from both parents. However, the details and identifying features like the dots, ridge enclosure and others are not genetically linked but influenced by the fetus environment, in other words, they are not inheritable.
Application of fingerprint in DNA
In the year 1984, scientists wanted to find out a way to distinguish individuals genetically. Alec Jeffries, a scientist at the University of Leicester realized that humans share 99.9% of the same genes. The genes are going to be the same but each one might have a different copy of the same genes making us different. At first, scientists disregarded the remaining o.o1% and even called it junk DNA till Alex Jeffries did more research into it.
Recap:Every human being has 23 pairs of chromosomes inherited from both parents. The chromosomes contain DNA that has been coiled like a thread. Inside the DNA are genes and non-coding DNA, also known as junk DNA.
The 0.01% genetic difference in humans lies in the junk DNA.
Alec Jeffries realized that the junk DNA contained repeating patterns of DNA that were different in every individual in terms of length. The patterns were called short tandem repeats (STRs). There was so much variability among the patterns of different people: some had short patterns whilst others had long patterns.
This was a breakthrough in science because we all share the same genes but this was different in each person. The fingerprint was used as a source of DNA because of its features. In other words, scientists were able to retrieve our DNA through our fingerprints. Other sources of DNA include saliva, hair follicles, blood, semen, urine and so on. This technique was called DNA fingerprinting which is used in crimes, paternity tests and so on.
Application of DNA fingerprinting
DNA is an overlap between genes from your mother and father. Scientists first extract DNA from fingerprints. Afterwards, they use a restriction enzyme to cut the DNA to derive the junk DNA. Mostly, DNA derived from individuals is small so scientists amplify it to obtain the short tandem repeats which differentiate us genetically. Then scientists pass it through a gel or a well to obtain the patterns. Since DNA is a combination of the genes from the mother and father, relatives will share a similar pattern.
This technique is used to identify a family link, paternity tests and criminals.
Use this technique to solve the puzzle below.
There is a rare case in which three babies are switched at birth in a hospital. The parents’ suspicions leak to the press and the hospital management team reacts to the media scandal, rushing to conduct paternity tests. Which baby belongs to each couple?
- Science Insights. The birth of genetic fingerprinting, an invaluable tool for CSI. Retrieved from https://www.bbvaopenmind.com/en/science/scientific-insights/the-birth-of-genetic-fingerprinting-an-invaluable-tool-for-csi/
- National library of medicine. Are fingerprints determined by genetics? Retrieved from https://medlineplus.gov/genetics/understanding/traits/fingerprints/#:~:text=Like many other complex traits, the pads of the fingers.&text=The basic size%2C shape%2C and,be influenced by genetic factors.
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