Each cell of the body of a living eukaryotic creature has a polymer DNA chain inside the nucleus, which is the main "program" of life. Human DNA is the genetic material on which all tribal memory is recorded, diseases that the individual is predisposed to, and all personality talents. A set of 23 paired genes - the basis of the human genetic apparatus
To understand how important DNA is, you need to know its structure and functions. DNA is not just a code, it is the basic matrix by which a cell builds proteins from amino acids and prepares new cells that will replace it over time. This ensures the life of the body.
Human genetics. Key Terms
Chromosomes, or chromatid filaments, are the center of the nucleus and provide the life of an individual cell and the whole organism. Chromosomes are made up of genes. A gene is a unit that carries the biological memory of ancestors. A set of human genes is called a genome.
The genetic apparatus includes the nucleus, and the DNA contained within it. DNA cannot exist without helpers — messenger RNA and transport — tRNA. We will remember about RNA later. Now let’s explain what DNA is.
A polymer of DNA is contained in chromosomes. Two interlocking chains are connected according to the principle of complementarity.
DNA, deoxyribonucleic acid, is a polymer molecule made up of nucleotide bricks. A DNA code is a specific sequence of 4 nucleotides given to a specific individual: adenine, thymine, guanine and cytosine.
What is a chromosome? A chromosome is a larger unit of organization of genetic material in a cell. It contains several thousand genes, "packed" in certain structures. Each chromosome consists of a centromere and two telomeres.
The nucleotide sequence in the chromosome is encrypted with information about the structure of the body's proteins. And when the signal arrives that the body needs a new protein, the DNA is bifurcated, copied, and reassembled in the right order.
Characteristics of the genetic apparatus
Our chromosome set has several fundamental characteristics. What did scientists manage to investigate, what properties does the gene carry? There are 3 main characteristics of human genes.
- Self preservation.
- Self-reproduction.
- Mutability.
The term "gene" was introduced into science by W. Johansen in 1909. What functions does this unit of heredity perform?
- The gene passes information to future generations.
- Provides recombination of information.
The genetic apparatus of a human cell created by nature is very reasonable and complex. Smaller units of the hereditary apparatus - genes - make up the larger and more compactly located chromatin strands. Two such threads are interconnected thanks to special proteins and centromere.
How is life span encrypted in DNA?
Old age is literally visible under a microscope, and deterioration can be determined by the state of the chromosome telomeres.
Chromosomal filaments, consisting of a sequence of genes, are gradually shortened after each division. The smaller the telomeres become after repeated cell division, the more vital material is spent. And, therefore, old age and the death of the body are inevitably approaching.
Diploid and haploid chromosome sets
The cells of some organisms have a haploid set of chromosomes, while others have a diploid set. What is the difference? In those animals that reproduce sexually, there is a double set of chromosomes in the nucleus - diploid. A person always has a diploid set.
All other less developed living beings have a single set in their cells - that is, they belong to the haploid.
DNA functions
The whole mechanism of the cell nucleus works in a single "mode", preventing malfunctions, so that the cell can perform its functions efficiently.
When a cell needs to create a new protein, the structure of which is encoded in DNA, the “factory" of proteins needs to copy this information and read it. This requires tRNA and mRNA.
Another important role of the genetic apparatus is to preserve its code, to transfer all available information about the development of previous generations to newborn children.
General information about human DNA
What is a deoxyribonucleic acid chain? The DNA chain is double. It is tightly packed in chromosomes so that all this information can fit into the nucleus, not exceeding 5 * 10 -4 in diameter. Whereas the total length of the unfolded chain of human DNA is almost 2 m.
A person has a “standard” set of 23 pairs of chromosomes in the cell — one pair from the mother, the other from the father; and 2 sex chromosomes - XX or XU.
For the first time, the volume structure of helical DNA was discovered by J. Watson and F. Crick. By the way, J. Watson was the first person whose DNA code was decrypted and published in a journal.
The polynucleotide chain is formed as a result of a complex condensation reaction of nucleic acids - purines and pyrimidines. Such acids always consist of 3 chemicals - pentose, a certain nitrogenous base and particles of phosphoric acid.
The consequences of chromosome mutations
The genetic apparatus is not only a material "repository" of important information, but also a completely living substance. Chromosomes move in the nucleus, divide when necessary.
The structure of chromosomes after each division remains the same. If even one mistake had occurred, the body would have already started to fail. After all, what determines DNA? It hides the biological properties of the karyotype - the particular form and color of the subject, the specifics of his entire internal and external organization. All organs work according to the scheme, which is recorded in the polynucleotide chain of each of its cells. It may be noted that DNA also contains a “work plan” for a somatic cell.
That is why any mutation in the chromosomes of a newborn sometimes leads to abnormalities, or worse, disability.
The role of RNA
Ribonucleic acid, or RNA, is also a nucleotide that can penetrate into the nucleus, "read" DNA information and copy the fragment necessary for protein synthesis. Matrix RNA reads in a certain way information about the structure of the protein that is needed, and calmly leaves the nucleus.
Then, on the basis of it, the nucleotides available in the body are selected according to the principle of complementarity - they are "delivered" to the tRNA assembly site - and a new protein is created. RNA and DNA work together. None of them can exist without the other.