Each cell of the body of a living eukaryote has a DNA polymer chain inside the nucleus, which is the main "program" of life. Human DNA is the genetic material on which all ancestral memory, diseases to which the individual is predisposed, and all the talents of the individual are recorded. A set of 23 paired genes is 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 main template by which the cell builds proteins from amino acids and prepares new cells that will replace it over time. This is how the life of the organism is ensured.
Human genetics. Basic terms
Chromosomes, or chromatid threads, are the center of the nucleus and provide life for a single cell and the whole organism. Chromosomes are made up of genes. A gene is a unit that carries the biological memory of ancestors. The set of human genes is called the genome.
The genetic apparatus includes a nucleus, andthe DNA it contains. DNA cannot exist without helpers - messenger RNA and transport - tRNA. Let's talk about RNA later. Now let's explain what DNA is.
DNA polymer is found in chromosomes. Two intertwining chains are connected according to the principle of complementarity.
DNA - deoxyribonucleic acid - is a polymer molecule consisting of building blocks of nucleotides. The DNA code is a specific sequence of 4 nucleotides given to a particular individual: adenine, thymine, guanine and cytosine.
What is a chromosome? A chromosome is a larger unit of organization of the genetic material in a cell. It contains several thousand genes, "packed" into certain structures. Each chromosome consists of a centromere and two telomeres.
The nucleotide sequence in the chromosome encodes information about the structure of the body's proteins. And when the signal comes that the body needs a new protein, the DNA splits, copies, and reassembles in the right order.
Characteristics of the genetic apparatus
Our chromosome set has several fundamental characteristics. What did the scientists manage to investigate, what properties does the gene carry? 3 main characteristics of human genes are known.
- Self-preservation.
- Self-play.
- Mutability.
The term "gene" was introduced into science by W. Johansen in 1909. What functions does this unit of heredity perform?
- Gene passes on information to the next generations.
- Provides information recombination.
The genetic apparatus of a human cell is created by nature in a very reasonable and complex way. Smaller units of the hereditary apparatus - genes - make up larger and more compactly arranged chromatin filaments. Two such threads are interconnected thanks to special proteins and a centromere.
How is lifespan encoded in DNA?
Old age is literally visible under a microscope, and deterioration can be determined by the state of chromosome telomeres.
Chromosomal strands, consisting of a sequence of genes, gradually shorten after each division. The smaller the telomeres become after repeated cell division, the more vital material is spent. And, therefore, old age and death of the body are inevitably approaching.
Diploid and haploid sets of chromosomes
In the cells of some organisms there is a haploid set of chromosomes, in others it is diploid. 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 are haploid.
DNA functions
The whole mechanism of the cell nucleus works in a single "mode", without allowing failures, so that the cell can perform its functions efficiently.
When a cell needs to create a new protein, the structurewhich is encrypted 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 strand is double. It is densely packed into chromosomes so that all this information can fit into the nucleus, which does not exceed 510-4 in diameter. Whereas the total length of the unfolded human DNA chain is almost 2 m.
A person has a "standard" set of 23 pairs of chromosomes in a cell - one pair from the mother, the other from the father; and 2 sex chromosomes - XX or XY.
For the first time, J. Watson and F. Crick discovered the three-dimensional structure of helical DNA. By the way, J. Watson was the first person whose DNA code was deciphered and published in a journal.
A 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 a particle of phosphoric acid.
Consequences of chromosome mutations
The genetic apparatus is not only a material "repository" of important information, but also a completely living substance. Chromosomes move around in the nucleus, dividing when needed.
Chromosome structure remains the same after each division. Ifthere was at least one mistake, the body would have already begun to malfunction. What defines DNA? It hides the biological properties of the karyotype - the features of the shape 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 can be noted that DNA also contains the "work plan" of the somatic cell.
That is why any mutation in the chromosomes of a newborn sometimes leads to anomalies, or worse, disability.
Role of RNA
Ribonucleic acid, or RNA, is also a nucleotide that can penetrate the nucleus, "read" DNA information and copy the fragment needed for protein synthesis. Messenger RNA reads in a certain way information about the structure of the protein that is needed, and quietly exits the nucleus.
Then, based on it, the nucleotides available in the body at the ready are selected according to the principle of complementarity - they are "brought" to the site of tRNA assembly - and a new protein is created. RNA and DNA work together. Neither can exist without the other.
