Nucleic acids play an important role in ensuring the vital activity of the cells of living organisms. An important representative of this group of organic compounds is DNA, which carries all the genetic information and is responsible for the manifestation of the necessary features.
What is replication?
In the process of cell division, it is necessary to increase the amount of nucleic acids in the nucleus so that there is no loss of genetic information in the process. In biology, replication is the duplication of DNA through the synthesis of new strands.
The main purpose of this process is to transfer genetic information to daughter cells unchanged without any mutations.
Enzymes and proteins of replication
Duplication of the DNA molecule can be compared to any metabolic process in the cell, which requires the appropriate proteins. Since replication is an important component of cell division in biology, therefore, many auxiliary peptides are involved here.
DNA polymerase is the most important reduplication enzyme that is responsible forfor the synthesis of the daughter chain of deoxyribonucleic acid. In the cytoplasm of the cell, in the process of replication, the presence of nucleic triphosphates is mandatory, which bring all the nucleic bases
These bases are nucleic acid monomers, so the entire chain of the molecule is built from them. DNA polymerase is responsible for the assembly process in the correct order, otherwise all kinds of mutations are inevitable.
- Primase is a protein that is responsible for the formation of a primer on the DNA template chain. This primer is also called a primer, it has the structure of RNA. For the DNA polymerase enzyme, the presence of initial monomers is important, from which further synthesis of the entire polynucleotide chain is possible. This function is performed by the primer and its corresponding enzyme.
- Helicase (helicase) forms a replication fork, which is a divergence of matrix chains by breaking hydrogen bonds. This makes it easier for polymerases to approach the molecule and begin synthesis.
- Topoisomerase. If you imagine a DNA molecule as a twisted rope, as the polymerase moves along the chain, a positive voltage will be formed due to the strong twisting. This problem is solved by topoisomerase, an enzyme that breaks the chain for a short time and unfolds the entire molecule. After that, the damaged area is sewn together again, and the DNA does not experience stress.
- Ssb proteins attach like clusters to DNA strands at the replication fork to prevent re-formation of hydrogen bonds before the end of the reduplication process.
- Ligas. Enzyme functionconsists in stitching Okazaki fragments on the lagging strand of the DNA molecule. This happens by cutting out primers and inserting native deoxyribonucleic acid monomers in their place.
In biology, replication is a complex multi-step process that is extremely important in cell division. Therefore, the use of various proteins and enzymes is necessary for efficient and correct synthesis.
Reduplication mechanism
There are 3 theories that explain the DNA duplication process:
- Conservative states that one daughter molecule of the nucleic acid has a matrix nature, and the second is completely synthesized from scratch.
- Semi-conservative proposed by Watson and Crick and confirmed in 1957 in experiments on E. Coli. This theory says that both daughter DNA molecules have one old strand and one newly synthesized.
- The dispersion mechanism is based on the theory that daughter molecules have alternating sections along their entire length, consisting of both old and new monomers.
Now scientifically proven semi-conservative model. What is replication at the molecular level? At the beginning, the helicase breaks the hydrogen bonds of the DNA molecule, thereby opening both chains for the polymerase enzyme. The latter, after the formation of seeds, begin the synthesis of new chains in the direction 5'-3'.
The property of DNA antiparallelism is the main reason for the formation of leading and lagging strands. On the leading strand, DNA polymerase moves continuously, while on the laggingit forms Okazaki fragments, which will be joined together by ligase in the future.
Features of replication
How many DNA molecules are in the nucleus after replication? The process itself implies a doubling of the genetic set of the cell, therefore, during the synthetic period of mitosis, the diploid set has twice as many DNA molecules. Such an entry is usually marked as 2n 4c.
In addition to the biological meaning of replication, scientists have found application of the process in various fields of medicine and science. If in biology replication is the duplication of DNA, then in the laboratory, the reproduction of nucleic acid molecules is used to create several thousand copies.
This method is called the polymerase chain reaction (PCR). The mechanism of this process is similar to replication in vivo, therefore, similar enzymes and buffer systems are used for its course.
Conclusions
Replication is of great biological importance for living organisms. The transfer of genetic information during cell division is not complete without duplication of DNA molecules, so the coordinated work of enzymes is important at all stages.
