Understanding the fundamental foundations of the existence of life is impossible without a clear understanding of the transmission of hereditary information and its implementation. The storage of body genes is realized through chromosomes in which different sections of DNA encoding the primary amino acid sequence of a particular protein are packed. And the realization of genetic information and its transmission by inheritance is achieved by copying it. This process is called "transcription." In biology, it means reading the code of a gene region and synthesizing a matrix for protein biosynthesis on its basis.
Molecular Transcription Basics
Transcription is an enzymatic process that is preceded by "unpacking" a DNA molecule and providing access to read a particular gene. Then, in the double-stranded DNA molecule at the initial site, hydrogen bonds between nucleotides are broken for 4 frames. From this moment, the phase of transcription initiation in biology begins, associated with the attachment of DNA-dependent RNA polymerase to the DNA macropolymer.
A logical outcome of the initiation is the synthesis of the starting region of the messenger RNA, and as soon as the first complementary nucleotide joins it and the DNA-dependent RNA polymerase translocates, we should talk about the beginning of the elongation stage. Its essence boils down to the gradual movement of DNA-dependent RNA polymerase along the DNA molecule in the direction of 3`-5`, dissection of the hydrogen bonds of the DNA in front and their restoration at the back, as well as the addition of a complementary nucleotide to the growing chain of the RNA matrix.
The enzyme DNA-dependent RNA polymerase catalyzes precisely the attachment of a nucleotide to RNA, while other enzyme systems are responsible for reading, separation of hydrogen bonds and their restoration. All of them are in the place where transcription occurs. Biology allows you to apply the method of labeled atoms and confirm the fact of their highest concentration in the nuclei of cells.
Chronology of transcription
In laboratory conditions, scientists at the Human Genome research group were able to artificially synthesize the DNA molecule itself and store the genetic code in it. This process took more than 2 decades, not counting the lengthy preparation. It is interesting how fast these processes take place in a living cell. The main research method for translation and transcription is molecular biology. Although it is still experiencing difficulties associated with the impossibility of demonstrating these processes, there is some evidence regarding protein biosynthesis time.
In particular, the process of “unpacking” genetic information can take 16-48 hours, and transcription of the desired gene can take about 4-8 hours. The synthesis of one small protein molecule based on messenger RNA will take about 4-24 hours, after which the stage of its "maturation" begins. By this is meant independent spontaneous packing of the protein into the secondary, and then into the tertiary structure. If the protein requires postsynthetic modification, then this process may take about a week or more.
The cellular structures where transcription and translation take place are studied in more detail in biology. At the same time, it was possible to calculate that in eukaryotic cells with a large set of genetic material, the synthesis of a simple insulin molecule takes about 16 hours. Genetically modified E. coli is able to synthesize such a molecule in 4 hours. In the case of large proteins of the tertiary and quaternary structure, the process of their synthesis and final formation can take about 2 weeks.
Localization of transcription enzymes
Such a process as transcription (in biology) takes place in the place of direct storage of hereditary information. In eukaryotic cells, this is the cell nucleus, and in pre-nuclear life forms - the cytoplasm. The viral enzyme reverse transcriptase works in the nucleus of infected cells. At the same time, mitochondrial nucleic acids, which are a set of genes, also go through the stage of transcription. In biology and genetics, the nature of these processes is still unknown.
But the fact of the presence of human mitochondrial diseases that are inherited by descendants confirms DNA replication, for which transcription is a necessary step. This means that such a process can occur in several cellular structures: in eukaryotes it is mitochondria and the cell nucleus, and in prokaryotes in the cytoplasm and plasmids.
Localization of biosynthetic processes
The localizations where transcription and translation take place (in biology) are different, because the synthesis of protein molecules simply cannot occur in the cell nucleus. The primary structure is assembled on the ribosomal apparatus of the cell, which is mainly concentrated in the cytoplasm on the membrane of the rough endoplasmic reticulum.
Synthesis in highly developed cells, which are characterized by a high assembly rate of new protein molecules, occurs predominantly on polyribosomes. But in bacterial cells and highly specialized cells, biosynthesis can occur on disparate ribosomes in the cytoplasm. Viral bodies do not have their own synthetic apparatus and organelles, and therefore exploit the structure of infected cells.