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 a school biology course, a minimal knowledge of genetics and heredity remains in my memory, since this complex topic is given to children only superficially. But this knowledge (the biological role of DNA, the effect on the body) can be incredibly useful.
To begin with, nucleic acids perform an important function, namely, they ensure the continuity of life. These macromolecules are presented in two forms:
They are transmitters of the genetic plan of the structure and functioning of body cells. Let's talk about them in more detail.
DNA and RNA
To begin with, which branch of science deals with such complex issues as:
- study of the principles of storage of hereditary information ;
- its implementation;
- broadcast;
- study of the structure of biopolymers;
- their functions.
All of this is being studied by molecular biology. It is in this branch of biological sciences that one can find the answer to the question of what is the biological role of DNA and RNA.
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 occurs in 1868. Then scientists managed to find them in the nuclei of leukocytes and sperm of the moose. A subsequent study showed that DNA can be found in all cells of plant and animal nature. The DNA model was introduced in 1953, and the Nobel Prize for discovery was presented in 1962.
DNA
Let's start this section with the fact that 3 types of macromolecules are distinguished:
- Deoxyribonucleic acid;
- ribonucleic acid;
- squirrels.
Now we will take a closer look at the structure and biological role of DNA. So, this biopolymer transmits data on heredity, developmental features not only of the carrier, but of all previous generations. The monomer of DNA is the nucleotide. Thus, DNA is the main component of chromosomes containing the genetic code.
How does the transfer of this information become possible? The whole point is the ability of these macromolecules to reproduce themselves. Their number is infinite, which can be explained by large sizes, and as a result, by a huge number of all kinds of nucleotide sequences.
DNA structure
In order to understand the biological role of DNA in a cell, it is necessary to familiarize yourself with the structure of this molecule.
Let's start with the simplest, all nucleotides in their structure have three components:
- nitrogen base;
- pentose sugar;
- phosphate group.
Each individual nucleotide in a DNA molecule contains one nitrogenous base. It can be absolutely any of four possible:
- A (adenine);
- G (guanine);
- Ts (cytosine);
- T (thymine).
A and G are purines, and C, T and U (uracil) are pyramidines.
There are several rules for the correlation of nitrogenous bases, called the rules of Chargaff.
- 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 for 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 - from 0.45 to 2.57.
The structure of each DNA molecule resembles a double twisted helix. Please note that polynucleotide chains are antiparallel in this case. That is, the location of the nucleotide pairs in one chain has the opposite sequence than in the other. Each turn of this helix contains as many as 10 nucleotide pairs.
How are these chains held together? Why is the molecule strong and does not break up? The thing is in 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 are the largest organic molecules, the length of which varies from 0.25 to 200 nm.
Complementarity
Let us dwell in more detail on pair relationships. We have already said that pairs of nitrogenous bases are formed not in a chaotic manner, but in strict sequence. So, adenine can only bind with thymine, and guanine only with cytosine. This sequential arrangement of pairs in one chain of the molecule dictates their location in another.
When replicating or doubling for the formation of a new DNA molecule, this rule, called "complementarity," is mandatory. You can notice the following pattern, which was mentioned in the summary of the rules of Chargaff - the same number of the following nucleotides: A and T, G and C.
Replication
Now let's talk about the biological role of DNA replication. To begin with, 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 (rupture of the original molecule on a mono chain and the addition of complementary bases to each of them);
- dispersed (decomposition of a molecule, replication of fragments, and collection at random).
The replication process has three stages:
- initiation (weaving DNA sites using the helicase enzyme);
- elongation (chain extension by the addition of nucleotides);
- termination (reaching the required length).
This complex process has a special function, that is, a biological role - ensuring the accurate transfer of genetic information.
RNA
They told what the biological role of DNA is, now we propose to proceed to the consideration of ribonucleic acid (i.e., RNA).
We begin this section with the fact that this molecule is no less important than DNA. We can find it in absolutely any organism, cells of prokaryotes and eukaryotes. This molecule is observed even in some viruses (we are talking about RNA-containing viruses).
A distinctive feature of RNA is the presence of one chain of molecules, but, like DNA, it consists of four nitrogen bases. In this case, it is:
- adenine (A);
- uracil (U);
- cytosine (C);
- guanine (G).
All RNAs are divided into three groups:
- matrix, which is usually called information (reduction is possible in two forms: mRNA or mRNA);
- transport (tRNA) ;
- ribosomal (rRNA).
Functions
Having dealt with the biological role of DNA, its structure and features of RNA, we propose 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 a DNA molecule to the nucleus cytoplasm. Also, mRNA is a matrix for protein synthesis. As for the percentage of this type of molecule, it is quite low (about 4%).
And the percentage of rRNA in the cell is 80. They are necessary, since they are the basis of ribosomes. Ribosomal RNA is involved in protein synthesis and polypeptide chain assembly.
The adapter that builds the amino acids of the chain is tRNA, which transfers amino acids to the field 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, they could not give obvious information on this subject, but even now far from everything is known about the significance of DNA and RNA.
If we talk about the general biological significance, their role is to transmit hereditary information from generation to generation, protein synthesis and coding of protein structures.
Many express this version: these molecules are associated 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.