In this article you can learn the biological role of DNA. So, this abbreviation is familiar to everyone from the school bench, but not everyone has an idea what it is. After the school biology course, minimal knowledge of genetics and heredity remains in memory, since children are given this complex topic only superficially. But this knowledge (the biological role of DNA, the effect it has on the body) can be incredibly useful.
Let's start with the fact that nucleic acids perform an important function, namely, they ensure the continuity of life. These macromolecules are presented in two forms:
- DNA (DNA);
- RNA (RNA).
They are transmitters of the genetic plan for the structure and functioning of body cells. Let's talk about them in more detail.
DNA and RNA
Let's start with what branch of science deals with such complexquestions like:
- studying the principles of storing hereditary information;
- its implementation;
- transmission;
- studying the structure of biopolymers;
- their functions.
All this is studied by molecular biology. It is in this branch of biological sciences that the answer to the question of what the biological role of DNA and RNA can be found.
These macromolecular compounds formed from nucleotides are called "nucleic acids". It is here that information about the body is stored, which determines the development of the individual, growth and heredity.
The discovery of deoxyribonucleic and ribonucleic acid falls on 1868. Then scientists managed to detect them in the nuclei of leukocytes and spermatozoa of elk. Subsequent study showed that DNA can be found in all cells of plant and animal nature. The DNA model was presented in 1953 and the Nobel Prize for discovery was awarded in 1962.
DNA
Let's start this section with the fact that there are 3 types of macromolecules in total:
- deoxyribonucleic acid;
- ribonucleic acid;
- proteins.
Now we will take a closer look at the structure, the biological role of DNA. So, this biopolymer transmits data on heredity, developmental features not only of the carrier, but also of all previous generations. The DNA monomer is a nucleotide. Thus, DNA is the main component of chromosomes, containing the genetic code.
How is the transmission of thisinformation? The whole point lies in the ability of these macromolecules to reproduce themselves. Their number is infinite, which can be explained by their large size, and as a result, by a huge number of various nucleotide sequences.
DNA structure
In order to understand the biological role of DNA in a cell, it is necessary to become familiar with the structure of this molecule.
Let's start with the simplest, all nucleotides in their structure have three components:
- nitrogenous base;
- pentose sugar;
- phosphate group.
Each individual nucleotide in the DNA molecule contains one nitrogenous base. It can be absolutely any of four possible:
- A (adenine);
- G (guanine);
- C (cytosine);
- T (thymine).
A and G are purines, and C, T and U (uracil) are pyramidins.
There are several rules for the ratio of nitrogenous bases, called Chargaff's rules.
- A=T.
- G=C.
- (A + G=T + C) we can transfer all unknowns to the left side and get: (A + G) / (T + C)=1 (this formula is the most convenient when solving problems in biology).
- A + C=G + T.
- The value of (A + C)/(G + T) is constant. In humans, it is 0.66, but, for example, in bacteria, it is from 0.45 to 2.57.
The structure of each DNA molecule resembles a double twisted helix. Note that the polynucleotide chains are antiparallel. That is, the location of the nucleotidethe pairs on one strand are in reverse order than those on the other. Each turn of this helix contains as many as 10 nucleotide pairs.
How are these chains fastened together? Why is a molecule strong and does not break down? It's all about the hydrogen bond between nitrogenous bases (between A and T - two, between G and C - three) and hydrophobic interaction.
At the end of the section, I would like to mention that DNA is the largest organic molecules, the length of which varies from 0.25 to 200 nm.
Complementarity
Let's take a closer look at pairwise bonds. We have already said that pairs of nitrogenous bases are formed not in a chaotic manner, but in a strict sequence. So, adenine can only bind to thymine, and guanine can only bind to cytosine. This sequential arrangement of pairs in one strand of a molecule dictates their arrangement in the other.
When replicating or doubling to form a new DNA molecule, this rule, called "complementarity", is necessarily observed. You can notice the following pattern, which was mentioned in the summary of Chargaff's rules - the number of the following nucleotides is the same: A and T, G and C.
Replication
Now let's talk about the biological role of DNA replication. Let's start with the fact that this molecule has this unique ability to reproduce itself. This term refers to the synthesis of a daughter molecule.
In 1957, three models of this process were proposed:
- conservative (the original molecule is preserved and a new one is formed);
- semi-conservative(breaking the original molecule into monochains and adding complementary bases to each of them);
- dispersed (molecular decay, fragment replication and random collection).
The replication process has three steps:
- initiation (unwinding of DNA sections using the helicase enzyme);
- elongation (lengthening of the chain by adding nucleotides);
- termination (reaching the required length).
This complex process has a special function, that is, a biological role - to ensure the accurate transmission of genetic information.
RNA
Told what the biological role of DNA is, now we suggest moving on to the consideration of ribonucleic acid (that is, RNA).
Let's start this section by saying that this molecule is just as important as DNA. We can detect it in absolutely any organism, prokaryotic and eukaryotic cells. This molecule is even observed in some viruses (we are talking about RNA-containing viruses).
A distinctive feature of RNA is the presence of a single chain of molecules, but, like DNA, it consists of four nitrogenous bases. In this case it is:
- adenine (A);
- uracil (U);
- cytosine (C);
- guanine (G).
All RNAs are divided into three groups:
- matrix, which is commonly called informational (reduction is possible in two forms: mRNA or mRNA);
- transport (tRNA);
- ribosomal (rRNA).
Functions
Having de alt with the biological role of DNA, its structure and features of RNA, we suggest moving on to the special missions (functions) of ribonucleic acids.
Let's start with mRNA or mRNA, the main task of which is to transfer information from the DNA molecule to the cytoplasm of the nucleus. Also, mRNA is a template for protein synthesis. As for the percentage of this type of molecules, it is quite low (about 4%).
And the percentage of rRNA in the cell is 80. They are necessary, as they are the basis of ribosomes. Ribosomal RNA is involved in protein synthesis and assembly of the polypeptide chain.
Adapter that builds amino acids of the chain - tRNA that transfers amino acids to the area of protein synthesis. The percentage in the cell is about 15%.
Biological role
To summarize: what is the biological role of DNA? At the time of the discovery of this molecule, no obvious information could be given on this matter, but even now not everything is known about the significance of DNA and RNA.
If we talk about the general biological significance, then their role is to transfer hereditary information from generation to generation, protein synthesis and coding of protein structures.
Many people also express this version: these molecules are connected not only with the biological, but also with the spiritual life of living beings. If you believe the opinion of metaphysicians, then DNA contains the experience of past lives and divine energy.
