[Kim Jaeho's Life Story]<254>The Mystery of Genes Created by DNA

Among the words we often use and hear today are DNA and genes, but how well do we truly understand their exact meanings and roles? DNA and genes are so small that they cannot be seen with the naked eye. It was only after the invention of the electron microscope and the advancement of research on living organisms that they gradually became known. Although much has been revealed with the development of genetics, there are still many aspects that remain unclear.

While new facts about genes will continue to be discovered, what has been established so far is that genes, which are made up of countless DNA molecules, carry information that serves as a channel to pass on the unique characteristics of living organisms to their offspring. It is also clear that genes play a central role in all activities of living organisms during their lifetime.

DNA is an abbreviation of Deoxyribonucleic acid, a biomolecule containing the genetic information necessary for the survival of living organisms. Most DNA is located inside the nucleus of cells, determining the functions and characteristics of the cells. Small amounts of DNA are also found in mitochondria, which produce energy within cells. Each human cell contains about 3 billion pairs, or 6 billion individual DNA molecules.

Looking at the structure of DNA, it is composed of three substances: sugar, phosphate, and bases. DNA molecules form a double helix backbone by connecting one sugar molecule and one phosphate molecule. The bases attached to the sugar molecules are linked in long chains and pair with complementary bases on another DNA strand, twisting together to form the double helix structure.

What we should focus on in the structure of DNA is that, unlike sugar or phosphate molecules which exist in only one type, there are four types of bases: adenine (A), thymine (T), guanine (G), and cytosine (C). These four bases can represent different meanings depending on their sequence, much like letters in a language. This sequence of bases is called the base sequence. For example, the base sequence ATGC has a different meaning from TACG.

Among the 3 billion pairs of DNA in our body cells, the base sequences in the cells of one person?whether liver cells, skin cells, or bone cells?are all the same regardless of cell type. Between people, 99.9% of DNA base sequences are identical, with only about 0.1% difference. This tiny difference influences our uniqueness, affecting various traits such as abilities, health, and behavior.

When the 6 billion DNA molecules in a single cell pair up, adenine (A) pairs only with thymine (T), and guanine (G) pairs only with cytosine (C). Therefore, among the 6 billion DNA molecules in a cell, only one side of the 3 billion pairs?3 billion DNA molecules?actually carries genetic information. But how much genetic information can be contained in these 3 billion DNA molecules?

Just as computers use two numbers, 0 and 1, to store and process infinite information, our body cells can store an enormous amount of genetic information by varying the sequence of the four bases A, T, G, and C. If the 3 billion DNA molecules in one cell were printed as letters like “AATGCTTA,” the printed height of the A4 paper, which holds 1,500 characters per page, would reach about 200 meters?an immense amount of information.

Now, let’s look at how genetic information is stored in genes through the relationship between DNA and genes. DNA molecules are connected in long chains ranging from a few hundred to over 2 million bases. Functionally, they act like programs that produce proteins or RNA molecules necessary for the body to perform specific functions. Such groups of DNA molecules that perform particular functions are called genes.

About 20,000 to 25,000 genes have been identified in a single cell. The DNA used to form these genes totals about 90 million bases, which is only about 1.5% of the entire DNA. The remaining 98.5% of DNA was once thought to have no function and was called junk DNA. However, in 2012, it was discovered that this DNA acts as switches that turn genes on or off.

What we need to pay attention to is that during all our activities, including rest and sleep, genes inside cells must be turned on to produce the necessary proteins or RNA molecules. For genes to be activated, switch DNA located in front of the genes must be appropriately turned on.

For example, when we eat carbohydrate-rich food, digestive enzymes called amylase must be produced in the salivary glands and pancreas. For this to happen, the switches of the genes that produce amylase in the salivary glands and pancreas must be turned on. No one directly flips these switches; it happens inside our bodies without our awareness.

Also, to feel joy upon hearing good news, brain cells must produce happiness substances such as endorphins, dopamine, and oxytocin. When food is digested and glucose is absorbed, blood sugar rises suddenly, so the pancreas produces insulin to lower blood sugar. The switches of the genes producing endorphins, dopamine, oxytocin, and insulin are turned on inside the body without our conscious knowledge.

Throughout our lives until the moment we die, including times when we are unconscious such as during sleep or under general anesthesia for surgery, our bodies never rest and continuously perform necessary activities. Behind these activities, genes work mysteriously without our awareness. The author calls this function of genes “the best master doctor prepared inside my body.”

How healthily we live depends on how well this best master doctor inside our body works. How well the master doctor works depends on how well we support its work inside our body.

If we maintain lifestyle habits that help the master doctor work well, our health can be kept at its best. This lifestyle is called Newstart. On the other hand, if we live in ways that hinder rather than help the master doctor, it is only natural that our body and mind deteriorate, making it difficult to maintain health.

Jaeho Kim, Independent Researcher