The laws of heredity have attracted the attention of man since those times when it became clear for the first time that genetics is something more material than some higher forces. Modern man knows that organisms have the ability to reproduce ones that are similar to themselves, while the offspring receives specific features and signs inherent in their parents. Reproduction is realized due to the ability to transmit genetic information between generations.
Theory: there is never too much
The laws of heredity began to be actively studied only relatively recently. An impressive step forward on this issue was made in the last century, when Sutton and Bowery put forward a new hypothesis to the public. It was then that they suggested: chromosomes probably carry genetic data. Somewhat later, technology allowed a chemical study of the chromosome composition. It revealed the presence of specific nucleic acid compounds of proteins. Proteins turned out to be inherent in a huge variety of structures and specific chemical composition. For a long time, scientists believed that it was proteins - the main aspect that ensures the transmission between generations of genetic data.
Several decades of research on this subject have provided new insights into the significance of cell DNA. As scientists have revealed, only such molecules are a material carrier of useful information. Molecules are an element of the chromosome. Today, almost any of our compatriots who have received a general education, as well as residents of many other countries, know very well how important DNA molecules are for a person, the normal development of the human body. Many represent the significance of these molecules in aspects of heredity.
Genetics as a science
Molecular genetics involved in the study of cell DNA has an alternative name - biochemical. This area of โโscience was formed at the intersection of biochemistry, genetics. A combined scientific direction is a productive field of human research, which has provided the scientific community with a large amount of useful information that is inaccessible to people engaged only in biochemistry or genetics. Experiments conducted by professionals in this area involve working with numerous life forms and organisms of various types and categories. The most significant results obtained by the scientific community are the results of the study of human genes, as well as various microorganisms. Among the latter, the most important are the Eicheria coli, the lambda phages of these microbes, the fungi of the neurospore Crassus and the saccharomyces cerevisia.
Genetic bases
For a long time, scientists have no doubt the importance of the chromosome in the transmission of hereditary information between generations. As shown by specialized tests, chromosomes are formed by acids, proteins. If you conduct an experiment with staining, the protein will stand out from the molecule, but the NK will remain in place. Scientists have more evidence to talk about the accumulation of genetic information in NK. It is through them that data is transmitted between generations. Organisms formed by cells, viruses with DNA, receive information from the previous generation through DNA. Some viruses contain RNA. It is this acid that is responsible for the transfer of information. RNA, DNA is NK, which are characterized by certain structural similarities, but there are differences.
Studying the role of DNA in heredity, scientists found that the molecules of such an acid have four types of nitrogen compounds and deoxyribose in their composition. Due to these elements, genetic information is transmitted. The molecule contains purine substances adenine, guanine, pyrimidine combinations thymine, cytosine. Chemical molecular backbone - sugar residues alternating with phosphoric acid. Each residue has a link to the carbon formula through sugars. Nitrogenous bases are attached on the sides to sugar residues.
Names and Dates
Scientists, exploring the biochemical and molecular foundations of heredity, were able to identify the structural features of DNA only in the 53rd. The authorship of scientific information is reserved for Crick, Watson. They proved that all DNA takes into account the biological specific qualities of heredity. When building a model, you need to remember about doubling the parts and the ability to accumulate, transmit hereditary information. Potentially, a molecule is capable of mutating. Chemical components, their combination, coupled with the approaches of x-ray diffraction studies, allowed us to determine the molecular structure of DNA as a double helix. It is formed by half spirals of antiparallel type. Saccharophosphate skeletons are strengthened by bonds with hydrogen.
In the study of the molecular foundations of heredity and variability, the works of Chargaff are of particular importance. The scientist devoted himself to the study of nucleotides present in the structure of nucleic acid. As it was possible to identify, each such element is formed by nitrogen bases, phosphorus residues, sugar. The molar content of thymine and adenine was revealed, and the similarity of this parameter for cytosine and guanine was established. It was suggested that every thymine residue has a pair of adenine, and for guanine there is cytosine.
The same, but so different
Studying nucleic acids as the basis of heredity, scientists determined that DNA belongs to the category of polynucleotides formed by numerous nucleotides. The most unpredictable sequences of elements in a chain are possible. Theoretically, the variety of serial has no limitations. DNAs have specific qualities associated with paired sequences of components, but base pairing occurs in accordance with biological and chemical laws. This allows you to predefine the sequence of different chains. This quality was called complementarity. It explains the ability of a molecule to perfectly reproduce its own structure.
When studying heredity and variability through DNA, scientists found: the strands that form the DNA are the matrices of the formation of complementary blocks. For the reaction to occur, the molecule unwinds. The process is accompanied by the destruction of hydrogen bonds. The bases interact with complementary components, which leads to the generation of specific bonds. After nucleotides are fixed, the molecule is crosslinked, leading to the appearance of a new polynucleotide formation, the sequence of parts of which is predetermined by the starting material. So two identical molecules appear, saturated with identical information.
Remark: guarantor of permanence and change
The above gives an idea of โโthe implementation of heredity and variability through DNA. The replication mechanism explains why DNA is present in every organic cell, while the chromosome is a unique organoid that reproduces with exceptional accuracy quantitatively and qualitatively. This method of material distribution was not feasible until the fact of the double helical complementary structure of the molecule was established. Crick, Watson, having previously suggested what the molecular structure is, turned out to be completely right, although over time, scientists began to doubt the correctness of their vision of the replication process. At first, it was believed that spirals from the same chain appear simultaneously. Enzymes that catalyze molecular synthesis in laboratory conditions, as it became known, work only in one direction, that is, one chain appears first, then the second.
Modern methods of studying human heredity have allowed simulating discontinuous DNA generation. The model appeared in the 68th. The basis for her proposal was experimental work using colic eicheria. The authorship of scientific work is assigned to Orzaki. Modern experts have accurate data on the nuances of synthesis in relation to eukaryotes, prokaryotes. From a genetic molecular fork, development occurs by generating fragments held together by a DNA ligase.
Assume that the synthesis processes are continuous. A replicative reaction involves numerous proteins. The weaving of the molecule occurs due to the enzyme, the preservation of such a state is guaranteed by a destabilizing protein, and the synthesis proceeds through polymerase.
New data - new theories
Using modern methods of studying human heredity, experts have identified where replication errors come from. The explanation became possible when accurate information appeared about the mechanisms of copying molecules and the specific features of the molecular structure. The replication scheme implies a divergence of the parent molecules, with each half acting as a matrix for the new chain. The synthesis is realized due to hydrogen bonds of the bases, as well as mononucleotide elements of the metabolic processes fund. In order for the bonds of thiamine, adenine or cytosine, guanine to be generated, the transition of substances into the tautomeric form is required. In the aquatic environment, each of these compounds is present in several forms; all of them are tautomeric.
There are more likely and less common options. A distinctive feature is the position of the hydrogen atom in the molecular structure. If the reaction proceeds with a rare variant of the tautomeric form, its result is the formation of bonds with an erroneous base. A DNA strand receives an incorrect nucleotide, the sequence of elements stably changes, a mutation takes place. The mutation mechanism was first explained by Crick, Watson. Based on their findings, a modern view of the mutation process is based.
RNA: features
Studying the molecular basis of heredity, scientists could not ignore a nucleic acid - RNA - no less important than DNA. It belongs to the number of polynucleotide and has structural similarities to that described previously. The key difference is the use of ribose as residues that serve as the foundation of the carbon skeleton. In DNA, recall, deoxyribose plays this role. The second difference: thymine is replaced by uracil. This substance also belongs to the class of pyrimidines.
Studying the genetic role of DNA and RNA, scientists first determined the relatively insignificant differences in the chemical structures of elements, but further studies of the topic showed that they play a huge role. These differences correct the biological significance of each of the molecules; therefore, the polynucleotides mentioned do not replace each other for living organisms.
Mostly RNAs are formed by a single strand, differ in size from each other, but most of them are smaller than DNA. Viruses containing RNA have in their structure such molecules created by two strands - their structure is as close to DNA as possible. In RNA, genetic data are accumulated and transmitted between generations. Other RNAs are divided into functional types. They are generated on DNA matrices. Catalysts of the process are RNA polymerases.
Information and heredity
Modern science, studying the molecular and cytological foundations of heredity, has identified nucleic acids as the main object of accumulation of genetic information - this applies equally to all living organisms. In most life forms, DNA plays a key role. The data accumulated by the molecule are stabilized by nucleotide sequences reproduced during cell division according to an invariable mechanism. Molecular synthesis proceeds with the participation of enzyme components, while the matrix is โโalways the previous nucleotide chain, which is transmitted materially between cells.
Sometimes, in biology and microbiology, students are given the task of solving genetics problems to demonstrate the dependencies. The molecular basis of heredity in such problems is considered both with respect to DNA and RNA. It must be remembered that in the case of a molecule whose genetics is RNA from a single helix, reproductive processes proceed according to a method similar to that described previously. The matrix is โโRNA in a form acceptable for replication. This appears in the cell structure due to infectious invasion. Understanding this process allowed scientists to refine the phenomenon of the gene and expand the knowledge base about it. Classical science understands the gene as a unit of information transmitted between generations and revealed in experimental works. The gene is capable of mutations, combined with other units of the same level. The phenotype that an organism possesses is explained precisely by the gene - this is its main function.
In science, the gene as a functional basis of heredity was initially considered also as the unit responsible for recombination, mutation. Currently, it is reliably known that these two qualities are the responsibility of the nucleotide pair included in DNA. But the function is provided by a nucleotide sequence of hundreds or even thousands of units that determine amino acid protein chains.
Proteins and their genetic role
In modern science studying the classification of genes, the molecular basis of heredity is considered in terms of the importance of protein structures. Any living matter is partially formed by proteins. They are considered one of the most significant components. Protein is a unique amino acid sequence that locally transforms in the presence of factors. Often there are two dozen types of amino acids, others are generated under the influence of enzymes from the main twenty.
A variety of protein qualities depends on the primary molecular structure, the amino acid polypeptide sequence that forms the protein. The experiments clearly showed that the amino acid has a strictly defined localization in the DNA nucleotide chain. Scientists have called it the parallels of protein elements and nucleic acids. The phenomenon is called colinearity.
DNA: features
Biochemistry and genetics, studying the molecular basis of heredity, are sciences in which special attention is paid to DNA. This molecule is classified as a linear polymer. As studies have shown, the only transformation available to the structure is the nucleotide sequence. It is responsible for encrypting the sequence of amino acids in a protein.
In eukaryotes, DNA is located in the cell nucleus, and protein generation occurs in the cytoplasm. DNA does not play the role of a matrix for the process of protein generation, which means that an intermediate element is required that is responsible for the transportation of genetic information. Studies have shown that the role is assigned to the RNA matrix.
As shown by the scientific work on the molecular basis of heredity, RNA is transferred from DNA to information. RNA can transfer data to protein and DNA. A protein receives data from RNA and sends it to the same structure. There are no direct links between DNA and protein.
Genetic information: it's interesting
As scientific works on the molecular foundations of heredity have shown, genetic data are inert information that is realized only with an external energy source and building material. DNA is a molecule that does not have such resources. A cell receives what it needs externally through proteins, then transformation reactions begin. There are three information paths that provide vital activity. They have connections among themselves, but are independent. Genetic data is transmitted by hereditary DNA replication. Data encoded by the genome - this stream is considered the second. Third, final - nutrient compounds that constantly penetrate the cell structure from the outside, providing it with energy and building ingredients.
The more highly structured the body, the more numerous elements of the genome. A diverse gene set implements the information encrypted in it through coordinated mechanisms. A cell saturated with data determines how to implement individual information blocks. . โ . โ , 61- . .