It is amazing to see how similar parents and children are. Or, on the contrary, they are completely different from brothers and sisters, and from father and mother. Why does it happen and what does it depend on? What structures are responsible for the preservation, consolidation, transmission and manifestation of signs in descendants from parents?
This role belongs to nucleic acids that form chromosomes. They are the molecules that perform the functions of all processes associated with heredity and variability. A special prerogative in this belongs to DNA molecules.
Nucleic Acid Discovery History
For a long time, such molecules were not known. However, in 1869, the scientist Micher, as a result of research, discovered a mixture of DNA and RNA, and then managed to establish their belonging to acids. He did this on the basis of the study of white blood cells in pus.
Since then, an active study of these compounds has begun. Many scientists have tried to establish the chemical composition of DNA and RNA. Understand their nature, the nature of the structure and the biological role. A great contribution to this matter was made by such people as:
- A.N. Belozersky.
- Thomas Morgan
- C. Bridges.
- A. Meller.
- G. de Vries.
- A. Stertevant.
- G.A. Nadson.
- A. S. Serebrovsky.
- N.P. Dubinin.
- T. S. Filippov and others.
In the period from 1900 to our time, the nature of nucleic acids, the chemical basis of the structure of DNA, its features and biological significance have been clarified. Discoveries have been made that make this molecule the universal basis of all life.
Research in the field of genetics made it possible to establish the relationship between DNA, the gene and chromosomes, and to decipher the genetic code of many living things. This was important for understanding the structure of wildlife, the mechanisms of its work.
The chemical composition of chromosomes was also determined . It was found that their basis is a nucleic acid molecule with a specific structure.
DNA: general description
The full abbreviation for the name is deoxyribonucleic acid. Along with RNA, this acid belongs to a number of nucleic acids. It got its name because sugar is part of the DNA . Its name is deoxyribose.
The chemical composition of DNA and RNA is very similar, the difference is precisely in the first place in the carbohydrate that forms the molecule. In RNA, this is ribose.
In general, a deoxyribonucleic acid molecule is a complex double-stranded macromolecule having a huge molecular weight and diverse composition. Therefore, most often the graphic image of this compound has the form of two threads, united by transverse steps - bonds.
In 1953, Charguff and his staff were able to uncover the completely internal structure and composition of the molecule, which was of great importance for all molecular biology and science as a whole. It became apparent that DNA contains five-carbon base sugar (pentose), purine and pyrimidine bases, and phosphoric acid residues.
This made it possible not only to further decipher the structure of the compound itself, but also to study properties, physical and chemical. The biological role and significance for the body was defined as fundamental, universal, and specific to each creature.
Chemical composition
If we characterize the internal atomic and molecular composition of a nucleic acid molecule, we can distinguish several main types of compounds:
- pentose - deoxyribose (carbohydrate monosaccharide);
- organic bases - purine (adenine and guanine), pyrimidine (cytosine and thymine);
- phosphoric acid residues with free bonds.
This, in general, is all the chemical basis of the structure of DNA. Another thing is that the combination of all these components is not simple, but a complex and unique process. So, interconnected deoxyribose, the base and the remainder of the inorganic acid together form a nucleotide. It is from nucleotide sequences that the entire structure of the molecule as a whole is formed.
Unique is the order in which the organic bases will be arranged one after another and in relation to the adjacent chain. The nucleotide sequence is constructed according to certain principles, the main of which is complementarity (strict correspondence between purine and pyrimidine components). This allows each living creature to have its own genetic code, unique, innate and deeply specific.
Phenotypically this manifests itself in the form of inheritance of completely different traits, in that there are no two identical people (except identical twins), distinctive features of appearance.
What kind of sugar does DNA contain?
The basis of any organic matter is a carbon chain of atoms. The DNA molecule was no exception. After all, the composition of DNA includes sugar, namely it consists of a sequence of five carbon atoms, combined into a cyclic structure. The same molecule is interrupted by an oxygen bridge entering the general cycle.
The chemical composition of sugar is expressed by the following empirical formula: C 5 H 10 O 4 . This molecule is aldopentose, which includes five carbon atoms twisted into a cycle. In addition, one of the chain atoms instead of the hydroxyl group contains only hydrogen, therefore, the prefix “deoxy” appeared in the name of sugar, that is, without oxygen.
The chemical composition of sugar was discovered and studied by Fibus Lieven, who discovered the whole structure and chemical nature of the compound in 1929.
Molecule Bases
The organic bases that make up DNA nucleic acid can be divided into two main groups.
- Purine - complex structures formed by two carbon cycles - five-membered and six-membered. These include adenine and guanine, which are complementary to pyrimidine bases in deoxyribonucleic acid.
- Pyrimidine - six-membered carbon cycles. This includes thymine and cytosine.
Thus, it turns out that the DNA contains sugar and a base, interconnected and bonded to bonds with a phosphoric acid radical . All together this is the nucleotide. In the double-stranded structure of a common DNA molecule, nucleotides bind to each other according to the complementarity rule: thymine base corresponds to adenine, and cytosine corresponds to guanine.
Types of bonds between particles
The main types of bonds between the component structures of DNA are as follows:
- hydrogen;
- covalent polar;
- intermolecular attraction forces;
- vaan der waltz interactions.
This allows the double-stranded structure to exist in three conformations:
- primary - linear nucleotide sequence;
- secondary - spirally twisted each thread and both near each other;
- tertiary - a complex conformational globule of a strongly spiralized molecule.
Thus, the fact that DNA is composed of sugar, bases and acid residues is the basis of its structure and soil for the implementation of a number of interactions and the formation of chemical bonds.
The Importance of DNA for Organisms
There are several most important points:
- The molecules of the acid in question are part of the chemical composition of the chromosomes that determine the individuality of all living organisms.
- DNA is the basis for the synthesis of complex polypeptide chains responsible for coding and transmission of hereditary traits.
- Deoxyribonucleic acid is the basis for transcription, that is, the primary synthesis of RNA, subsequently protein.
Such processes occur in all organisms. This allows us to call this structure the universal unit of all living things.
Molecule replication
This process is a doubling of the DNA molecule, occurring spontaneously with the expenditure of energy in living organisms. The main component in this case is DNA polymerase, an enzyme that catalyzes and controls the entire synthesis.
The essence of replication is that each of the strands of the molecule is divided and double its linear sequences. As a result of the process, two new DNA molecules are formed, each of which contains one old polypeptide chain, and the second a completely new one, constructed according to the principle of complementarity.
The significance of the process is to provide the offspring with genetic information in full.