At the end of the twentieth century, the mapping of the human genome was completed. Humanity had, at last, fulfilled its great dream – becoming the absolute master of life and death!? Celebrating a “victory” over the Book of Genesis and envisioning the paradise it intended to create, it forgot about the flaming sword and the cherubim, beings who guard the path that leads to the tree of life!
This is how scientists think about the “tree of life”.
The complete set of genes possessed by a living organism is called the genome. Genes determine the structure and function of every component of the body and brain of living beings. They are the recipes for making proteins. All the cells that make up the body and brain of living beings contain the same amount of inherited genes; what makes them different is the particular combination of genes that are active in each cell.
The human genome is composed of 23 pairs of chromosomes. Chromosomes consist of genes in DNA chains. Each chromosome contains only a single DNA molecule. Every species of living organism has its own characteristic number of chromosomes (the diploid number).
DNA and RNA molecules are nucleic acids, and both are found in the nuclei of all cells, with RNA molecules also present in the cytoplasm. A DNA molecule consists of two chains of nucleotides that coil around each other, forming a shape called the double helix. The sequence of nucleotides along these strands constitutes the language of life. The combination of any three of the four different types of nucleotide bases forms a coding unit. Arranged into genes, these coding units dictate the order of some of the twenty different kinds of amino acids that form a protein. An RNA molecule consists of a single chain of nucleotides and resembles a ladder split lengthwise.
Each cell has a complex system for reading and translating the hereditary information of genes into protein structure. Proteins control all functions in the organism. In cooperation with RNA molecules, and with the help of programmed systems for gene control and for the correction of gene copying, they enable the process of copying DNA molecules, which ensures the continuity of living matter. During reproduction, the DNA helices are separated with the help of a special protein, and then each half-strand synthesizes an identical counterpart from nucleotide building blocks that “float” in the viscous fluid of the cell nucleus. Besides being able to make copies of themselves, DNA molecules also direct the cell’s activity (metabolism). They do this by synthesizing another nucleic acid, messenger RNA, a courier that leaves the nucleus for the cell periphery, where it controls the construction of a given enzyme, at the right time and in the right place. The RNA molecule carries the coded information taken from DNA to the ribosomes, which “read” the codes, correctly join amino acids, and synthesize the corresponding proteins. Enzymes are active substances that enable the transformation of matter in the cell without themselves being altered. They consist of long chains of amino acids. The order of their components determines the working capacity of each enzyme.
The human DNA ladder is about a billion nucleotides long. The vast majority of nucleotide combinations are meaningless! Namely, they would trigger the synthesis of a protein that serves no useful function. Only an exceedingly small number of nucleotide combinations is useful for the functioning of complex life forms such as humans. Yet the number of useful combinations is so large that it likely exceeds, many times over, the total number of protons and electrons in the universe!