Each of us has a piece of unique genetic information that we carry within us called DNA. That molecule is made up of many tinier pieces called genes. Each person has two copies of each gene, one inherited from the mother and the second inherited from the father.
More than 99% of genes we share with each other. It means that only less than 1% of the genes are the same in every human being. It contributes to each person's unique physical characteristics, such as face shape, eye color, hair color, and height. Gene mutations that occur across the DNA are also one of the reasons that contribute to these differences. These mutations arise not only in humans but also in animals and plants. Let's take a closer look at it.
Image credit – Magdalena Osial
Generally, DNA is a chain of molecules composed of only four types of nucleotide subunits. Compared to LEGO® bricks, it is a long chain consisting of four kinds of bricks. This sequence makes us similar and differ from each other. A gene is a functional piece of DNA that translates chemical signals into messages about human appearance, health, and physical well-being. In other words, a gene is a combination of chemicals contained in each cell determining everything about us, including the color of the hair, skin, eyes, shape of the nose, ring hand or left-hand domination, or even the predispositions to develop some diseases.
Sometimes, during life, these genes can be changed by occurring mutations. A gene mutation is a change in the DNA molecules’ chain. It means that particular molecules in the gene are substituted with other molecules that should not be there by default. Some mutations could be repaired by cells but sometimes are permanent. Sometimes the mutations can cause the disease but some work in its favor, for example, giving it more excellent resistance to various conditions, including heart disease.
What causes errors during copies of genetic information? They might be connected with what we inherit in our genes or may appear in our lifetime. If the parent carries the gene mutation, it may or may not pass on to their child. Inherited mutations exist in almost every cell in a person's body and are present throughout their life. Following, if the mutations are inherited from parents, the copy process is transferred to the new cell. Mutations that appear in the course of life which are not inherited from the parents are called somatic mutations. They only affect specific cells. Their reasons are different: the action of the sun's ultraviolet radiation, chemicals, drugs, or even poor-quality diets. They are not inherited from parents to their children.
Image credit: Christoph Bock, Max Planck Institute for Informatics via Wikimedia Commons, CC-BY-SA-3.0
Somatic mutations can arise for several reasons. Let’s talk about a few of them. Throughout the entire human life, the body constantly creates new cells. Within this process, the complete genetic information (DNA) is copied in DNA replication. Sometimes, during the copy process, if errors are made and not corrected in time, mutations are generated.
Interestingly, not only during DNA replication but independent from this process, the DNA can self-destruct. Amazingly, the cell has its own repair mechanism, thanks to which it can repair any damage that has arisen. Nowadays, it’s evident that mutations can also occur due to exposure to environmental factors such as smoking, sunlight, and radiation. During these events, the single-molecule, the single bricks, or a chain of bricks could be deleted or substituted by other bricks. Through such processes, the DNA changes and consequently produces altered products.
Genetic mutations may also be connected with factors that we do not even suspect. An excellent example of such a mutation is Fatal Familial Insomnia (FFI), a rare and cruel condition. Only around 160 people in the world suffer from that illness.
Mutations inside the gene responsible for this disease make the body produce abnormally-shaped (misfolded) prion defective protein, also known simply as a “prion”, which is toxic to the body, especially to nerve cells. Why? Prions are gathering in these cells and damaging them.
The origin of this mutation has not been fully elucidated. Still, it is suspected that most of these people have one common ancestor. It probably was an Italian man born in the XVII century. This man most likely has a gene mutation that caused this disease. Before the symptoms of the disease appeared, he managed to pass the defective gene to his children. Symptoms of FFI at the beginning are similar to normal temporary Insomnia.
People who suffer can not fall asleep. That situation becomes chronic and progressive. The lack of sleep leads to a deficient mental and physical patient’s condition. Lack of sleep is the most characteristic symptom, but others like dementia, problems with language or memory may occur.
There is a big difference between FFI and classical Insomnia (the condition in which the sleep duration is insufficient or its quality is unsatisfactory) – sleeping pills do not help. It is the other way around; drugs are making the situation worse. It accelerates the disease. In the end, the ill patient falls into a coma and dies later.
Another rare genetic mutation is hypertrichosis (“werewolf syndrome” or Ambras syndrome). It is a hereditary genetic disorder, which causes excessive body hair. However, it can also develop with time as a result of other diseases like cancer. Only fifty such cases have been recovered since the Middle Ages. It is hard to live with this mutation taking into account social factors.
However, there are worse times like severe combined immunodeficiency disorder (SCID), also called the boy in the bubble disease. It is the condition in which people are born without an effective immune system. It causes defects in the T and B cell responses, which negatively affects the production of lymphocytes (a type of white blood cell involved in the immunologic response). It was the first disease to be treated with gene therapy (a therapy that uses genes to treat or prevent some diseases). A defective gene can also cause cancer. Mutations often cause this disease in many of the genes that control growth. Such genes may be in us from birth, but they do not always need to be activated (cause cancer).
In turn, an example of a potentially harmless genetic mutation is the color of the eyes. The blue color of an eye comes from genetic mutations. That is not the only example of the mutation in the. Some people do have skin in almost white color due to the lack of the natural pigment called melanin. That condition is called albinism, and it may appear not only in humans but also in the animal world. Albinism is caused by genetic mutations that occur naturally in particular organisms.
Generally, genetic mutations occur naturally in nature, with humans and plants or animals. Probably, many times you have seen in a grocery a food marked as GMO-free. In fact, plants that we eat also are genetically modified by nature. Just take a look at the eggplant. It has a cucumber-like shape and a dark violet color, and in such a form, it is the most popular. In the past, the eggplant looked utterly different. It has a round shape and white color, looking just like an egg. That is why it was named eggplant.
Some genetic mutations are made for this purpose. If we would take a look in the catalog of the seeds of decorative flowers, some of them would never grow in wild nature because genetic mutations created them. For example, some tulips of roses have a specific color, and the shape of petals is also non-usual—all due to the genetic mutations in plants.
What about seeds? Barley, wheat, and rye have gluten – a natural compound that makes the dough sticky while baking. Thanks to that compound, the bread does not break too much and is quite elastic. The seeds that we grow worldwide have much gluten, while they had much less of that compound in the past. All thanks to genetic mutations responsible for changing some features of the organism.
How often does the mutation occur, and whether does it happen randomly? The consequences of mutations, i.e., whether they are beneficial or not for the organism, do not affect their frequency of occurrence. Additionally, beneficial mutations that occur during the individual's lifetime are not passed on in the genes to the progeny. The probability of different mutations occurring varies. Some are more likely to happen than others. Some of them are favored by the biochemical reactions taking place.
Nature is full of mystery, so some genetic mutations can have dramatic consequences, while others have beneficial or neutral effects. It depends on the locations of gene change and the number of particular mutations. Evolutionary change comes from accumulating many mutations that would have negligible effects when they would appear solely.
Did you know that the food we eat today differs from the food served in recent centuries due to genetic mutations? Let’s take a look at the eggplant. It has a long shape and dark violet color, while it looked like an egg for its color and shape in the past. Because of some naturally occurring genetic mutations, such a plant had become entirely different to look at.
Summary
Somatic gene mutations appear spontaneously. They are changes in DNA sequences that cause changes in the gene sequence. The genetic mutation process takes place at errors during DNA replication or as a result of errors in DNA repair mechanisms. Environmental factors such as ultraviolet light, chemical carcinogens, drugs, or a direct response to stress can cause mutations. Genetic mutations can cause diseases, be neutral or contribute to better functioning of the cell. Mutations can be passed onto future generations.
This article is a joint work of Jakub Hilus (Faculty of Chemistry, University of Warsaw), Natalia Zawrotna (Faculty of Chemistry, University of Warsaw; Genegoggle, Warsaw), Agnieszka Pregowska (Institute of Fundamental Technological Research, Polish Academy of Sciences), and Magdalena Osial (Faculty of Chemistry; University of Warsaw, and Institute of Fundamental Technological Research, Polish Academy of Sciences) as a part of the Science Embassy project. Image Credit: Magdalena Osial.
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