Decoding the whole gene, will people be immortal?

On May 17, 2006, the Nature journal (a No. 1 scientific journal in the world) published an important article: After 10 years of work, an international scientific group completed the entire decoding. human genes. This is considered one of the most important works of the century, because this success opens a new era in the effort to conquer human illness.

Twenty-three human chromosomes.Chromosome 23 is named XY (sex determination)

In a famous song, Trịnh Công Sơn argued that our bodies were formed by 'dust', and finally returned to dust: Which dust particles killed me / Let me go tomorrow make sand. It is possible that at the time of writing this lyrics the musician was influenced by Buddhist philosophy, but he probably did not know molecular biology, a science that just started to develop in the 1980s, But in general, that immortal lyrics reflect very well the most basic unit of man. That 'sandy' unit can be described as a gene, or more precisely, DNA (which we know in French as DNA).

What is a gene?

Today through the advances of molecular biology, it is well known that the most basic biological unit in a human being is cells. Our bodies are made up of about 60,000 billion cells (other estimates suggest that this figure is 100,000 billion). Many cells have different tasks, such as brain cells that keep memory and knowledge, heart cells that make our heart beat smoothly, intestinal cells make mucus, etc. This cell has a certain lifetime. For example, male sperm cells only live for a few months, while female egg cells can last for up to 50 years.

Although different in function and duration of survival, all cells have the same structure: each cell has a nucleus (nucleus) in the middle (Figure 1). Each human average has about a billion DNA materials (deoxyribo-nucleic acid). The DNA material actually consists of four bases: A (adeline), C (cytosine), G (guanine), and T (thymine).

These letters form chromosomes (Figure 2). The human body has 23 chromosomes, codes 1 to 23, sorted by size (Figure 3). For example, the largest chromosome number 1 (containing the most genes or the most letters), followed by chromosome 2 (less genes than chromosome 1), until chromosome 23 has fewer genes more than chromosome 22. Each chromosome has many genes. For example, chromosome 1 has 3,141 genes, twice as much as the average chromosome. Chromosome 23 is actually named XY and functions to determine the sex of humans. Females have XX chromosomes, and males have XY chromosomes. During conception, the fetus receives a chromosome from the mother and a chromosome from the father (possibly X or possibly Y). The chromosome from the mother is always X, but the chromosome from the father may be X or it may be Y. Therefore, if the fetus receives X from the mother and X from the father, the fetus is a girl; but only one Y chromosome is the male.

The gene is actually a piece of DNA. A DNA array is a group of three letters called trinucleotide (which can be roughly translated as three letters), such as the GCC TCA TAG. One gene is a collection of three such patterns. For example, in Figure 4 illustrates a segment of the TGA sequence of genes CTG ACT.

It can be said in a similar way by using the book as an example: In the book there are 23 chapters (chromosomes); Each chapter has many stories (genes); Each story has many passages (exons); each paragraph has many words (codons); and each letter is written in bases.

Genes have the function of sending chemical signals to all parts of the body. These signals contain a full range of information and specific instructions for how our bodies work. Understanding the number of genes as well as the organizational structure of genes in the human body is a necessity to bring about new and important advances in biomedical. But not all genes have a clear function. In fact, about 47% of genes have no specific function (or we don't know their function yet).

How many genes does the human body have?

In the past, when gene decoding was incomplete, scientists estimated that the human body had about 100,000 genes. By 2001, when the first decoding results were announced, this number dropped to 30,000 to 40,000 genes. But now, after gene decoding is complete, scientists estimate that the human body contains only about 20,000 to 25,000 genes. Thus, the number of genes in humans may be lower than the number of genes in mice (about 30,000 genes)!

It is quite surprising that the number of genes in our body is less than the number of genes in . rice! In 2002, scientists also deciphered the genetic map of rice and discovered that indica water rice (also known as bulu in Indonesia) has about 32,000 to 56,000 genes.

Why do humans have fewer genes than rice? This question has been an interesting subject of scientific debate. It is important to note that although there are some genes with the same DNA structure between humans and rice, there is no evidence that genes are transferred between rice and humans. In other words, genetically modified foods or fruits may not alter the human genetic structure.

Genetic variations and effects

Each of us has 25,000 genes in the body. For example, you and I both carry genes like VDR, COLIA1, apoE4, etc. But the difference between you and me is the gene variant, not the gene. The gene is actually just an entity with a name, or in math, is a variable. Such as height, weight, age, gender, etc. are variables. Each variable has many values: my height is 175 cm, your height is 180 cm, and many others may be higher or lower. But sex has only two 'values', or more accurately, groups: male or female. Each gene has many groups that the term is called genotype.

Each variation is made up of two allele: an element received from the father, and one from the mother. For example, the VDR gene has two elements, T and G, and therefore has three variants: TT, TG and GG. Readers can carry in the TT variant, but I have the TG variant. For any gene, the frequency of genes often differs among ethnic groups. For example, in Asians, about 5% carry the GG variant of the VDR gene, but this frequency in white people is 15%. We are different because of genetic variation, not different because of genes.

In addition to determining the characteristics of the human body, the gene also functions . to cause illness. Once a mutated gene (ie a DNA fragment suddenly changes, such as from TGCCA to TCCCA, for example) can cause cell disorders, disease, even death. Only such a small change can make us suffer for a lifetime! The problem for 21st century medicine is how to track genes that affect diseases. Hopefully, through decoding the human genome, in the future, scientists will find these 'culprit genes'.

In addition to the function of using genetic information to diagnose diseases, genes can also be used to determine the effects of medicines. Everyone knows that any disease, medicine only works (that is, works well) for about 50% of patients, and 50% of patients have no effect, even harm. Many recent research evidence suggests that differences in drug effects between individuals may be caused by genes.

So one of the greatest challenges of medicine in the future is to determine which genes affect the effects of drugs. That also means, not when the human genome has been decoded, people will have no illnesses to turn their dream of life into reality.

Nguyen Van Tuan (Garvan Institute of Medicine, Sydney - Australia)