The laws of heredity have attracted human attention since the time when it first became clear that genetics is something more material than some higher powers. Modern man knows that organisms have the ability to reproduce similar to themselves, while the offspring receive specific features and characteristics inherent in their parents. Reproduction is realized due to the ability to transfer genetic information between generations.
Theory: You can never have too much
The laws of heredity began to be actively investigated only relatively recently. An impressive step forward in this matter was made in the last century, when Sutton and Boveri brought a new hypothesis to the public. It was then that they suggested that chromosomes probably carry genetic data. Somewhat later, technology allowed the chemical study of the chromosome composition. It revealedthe presence of specific nucleic 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 that were the main aspect that ensured the transfer of genetic data between generations.
Decades of research on this subject have provided new insight into the importance 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, are well aware of how significant DNA molecules are for a person, the normal development of the human body. Many imagine the significance of these molecules in terms of heredity.
Genetics as a science
Molecular genetics, which deals with the study of cell DNA, has an alternative name - biochemical. This area of science was formed at the intersection of biochemistry and genetics. The combined scientific direction is a productive area of human research, which has provided the scientific community with a large amount of useful information that is not available to people involved only in biochemistry or genetics. Experiments conducted by professionals in this field involve working with numerous life forms and organisms of various types and categories. The most significant results obtained by the scientific community are the result of the study of human genes, as well as variousmicroorganisms. Among the latter, among the most important are Eisheria coli, lambda phages of these microbes, neurospore crassa fungi and Saccharomyces cerevisia.
Genetic bases
For a long time, scientists have no doubt about the importance of the chromosome in the transfer of hereditary information between generations. As specialized tests have shown, chromosomes are formed by acids, proteins. If you conduct a staining experiment, the protein will be released from the molecule, but the NA will remain in place. Scientists have a greater amount of evidence that allows us 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 that have DNA, receive information from the previous generation through DNA. Some viruses contain RNA. It is this acid that is responsible for the transmission of information. RNA, DNA are NK, which are characterized by certain structural similarities, but there are also differences.
Studying the role of DNA in heredity, scientists have found that the molecules of such an acid contain four types of nitrogen compounds and deoxyribose. Due to these elements, genetic information is transmitted. The molecule contains purine substances adenine, guanine, pyrimidine combinations thymine, cytosine. The chemical molecular backbone is sugar residues alternating with phosphoric acid residues. 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,investigating the biochemical and molecular foundations of heredity, they were able to identify the structural features of DNA only in the 53rd. The authorship of scientific information is assigned to Crick, Watson. They proved that any DNA takes into account the biological specific qualities of heredity. When building a model, one must remember about the doubling of parts and the ability to accumulate and transmit hereditary information. Potentially, the molecule is able to mutate. Chemical components, their combination, coupled with the approaches of X-ray diffraction studies, made it possible to determine the molecular structure of DNA as a double helix. It is formed by halves of antiparallel type spirals. The sugar-phosphate backbones are reinforced with hydrogen bonds.
In the study of the molecular basis of heredity and variability, the works of Chargaff are of particular importance. The scientist devoted himself to the study of the nucleotides present in the structure of the nucleic acid. As it was possible to reveal, each such element is formed by nitrogen bases, phosphorus residues, sugar. Correspondence of the molar content of thymine and adenine was revealed, and the similarity of this parameter for cytosine and guanine was established. It was assumed that every thymine residue has a paired adenine, and for guanine there is a cytosine.
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, serial diversity has norestrictions. DNA has specific qualities associated with the paired sequences of its components, but base pairing occurs according to biological and chemical laws. This allows you to predefine sequences of different chains. This quality is called complementarity. It explains the ability of a molecule to perfectly reproduce its own structure.
When studying heredity and variability through DNA, scientists discovered that the strands that form DNA are the templates for the formation of complementary blocks. For a reaction to occur, the molecule unwinds. The process is accompanied by the destruction of hydrogen bonds. Bases interact with complementary components, which leads to the generation of specific bonds. After the nucleotides are fixed, the crosslinking of the molecule occurs, leading to the appearance of a new polynucleotide formation, the sequence of parts of which is predetermined by the starting material. This is how two identical molecules appear, saturated with identical information.
Replica: a guarantor of permanence and change
Described above gives an idea of the 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 quantitatively and qualitatively with exceptional accuracy. This method of real distribution was not feasible until the fact of the double helical complementary structure of the molecule was established. Crick, Watson, having previously assumed what the molecular structure was, 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 one chain appear simultaneously. Enzymes that catalyze molecular synthesis in the laboratory are known to work only in one direction, that is, first one chain appears, then the second.
Modern methods of studying human heredity have made it possible to simulate discontinuous DNA generation. The model appeared in the 68th. The basis for her proposal was experimental work using Eicheria coli. The authorship of scientific work is assigned to Orzaki. Modern specialists have accurate data on the nuances of synthesis in relation to eukaryotes, prokaryotes. From the genetic molecular fork, development occurs by generating fragments held together by DNA ligase.
The synthesis processes are assumed to be continuous. The replicative reaction involves numerous proteins. The unwinding of the molecule occurs due to the enzyme, the preservation of this state is guaranteed by the destabilizing protein, and the synthesis proceeds through the 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 about the mechanisms of copying molecules and the specific features of the molecular structure appeared. The replication scheme assumesdivergence of parent molecules, with each half acting as a matrix for a new chain. Synthesis is realized due to hydrogen bonds of bases, as well as mononucleotide elements of the stock of metabolic processes. In order to generate bonds of thiamine, adenine or cytosine, guanine, the transition of substances to the tautomeric form is required. In the aquatic environment, each of these compounds is present in several forms; they are all 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, it results in the formation of bonds with the wrong base. The DNA strand receives an incorrect nucleotide, the sequence of elements changes stably, a mutation occurs. The mutational mechanism was first explained by Crick, Watson. Their conclusions form the basis of the modern idea of the mutation process.
RNA features
Studying the molecular basis of heredity, scientists could not ignore no less important than DNA nucleic acid - RNA. It belongs to the group of polynucleotides and has structural similarities with those described earlier. The key difference is the use of ribose as the residues that act as the foundation of the carbon backbone. In DNA, we recall, this role is played by deoxyribose. The second difference is that 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 relativelyinsignificant differences in the chemical structures of the elements, but further study of the topic showed that they play a colossal role. These differences correct the biological significance of each of the molecules, so the mentioned polynucleotides do not replace each other for living organisms.
Mostly RNA is formed by one strand, differs from each other in size, 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 as possible to DNA. In RNA, genetic data is accumulated and passed between generations. Other RNAs are divided into functional types. They are generated on DNA templates. The process is catalyzed by 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 equally applies to all living organisms. In most life forms, DNA plays a key role. The data accumulated by the molecule are stabilized by nucleotide sequences that are reproduced during cell division according to an unchanged mechanism. Molecular synthesis proceeds with the participation of enzyme components, while the matrix is always the previous nucleotide chain, which is materially transmitted between cells.
Sometimes students in the framework of biology and microbiology are given the solution of problems in genetics for a visual demonstration of dependencies. The molecular bases of heredity in such problems are considered as relative to DNA,as well as RNA. It must be remembered that in the case of a molecule whose genetics is recorded by RNA from one helix, reproductive processes proceed according to a method similar to that described earlier. The template is RNA in a form that can be replicated. This appears in the cellular 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 work. 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 a unit responsible for recombination, mutation. At present, 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 and even thousands of units that determine the 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 significance of protein structures. All living matter is partially formed by proteins. They are considered one of the most significant components. Protein is a unique amino acid sequence that transforms locally whenpresence of factors. Often there are two dozen types of amino acids, others are generated under the influence of enzymes from the main twenty.
The diversity of protein qualities depends on the primary molecular structure, the amino acid polypeptide sequence that forms the protein. The experiments performed clearly showed that the amino acid has a strictly defined localization in the DNA nucleotide chain. Scientists called it the parallels of protein elements and nucleic acids. The phenomenon is called colinearity.
DNA features
Biochemistry and genetics, which study the molecular basis of heredity, are sciences in which special attention is paid to DNA. This molecule is classified as a linear polymer. Studies have shown that the only transformation available to the structure is the nucleotide sequence. It is responsible for encoding the sequence of amino acids in the protein.
In eukaryotes, DNA is located in the cell nucleus, and protein generation takes place in the cytoplasm. DNA does not play the role of a template for the process of protein generation, which means that an intermediate element is needed that is responsible for the transport of genetic information. Studies have shown that the role is assigned to the RNA template.
As shown by the scientific work devoted to the molecular bases of heredity, information is transferred from DNA to RNA. RNA can carry data to protein and DNA. The protein receives data from the RNA and sends it to the same structure. There are no direct links between DNA and proteins.
Geneticinfo: this is interesting
As scientific works devoted to the molecular bases of heredity have shown, genetic data is inert information that is realized only in the presence of an external energy source and building material. DNA is a molecule that does not have such resources. The cell receives what it needs from the outside through proteins, then transformation reactions begin. There are three information paths that provide life support. They are connected to each other, but independent. Genetic data is transmitted hereditarily by DNA replication. The data is encoded by the genome - this stream is considered the second. The third and final one is nutritional compounds that constantly penetrate into the cellular structure from the outside, providing it with energy and building ingredients.
The more highly structured the organism, the more numerous elements of the genome. A diverse gene set implements the information encrypted in it through coordinated mechanisms. The data-rich cell determines how to implement individual information blocks. Due to this quality, the ability to adapt to external conditions increases. The diverse genetic information contained in DNA is the foundation of protein synthesis. Genetic control of synthesis is a theory formulated by Monod and Jacob in 1961. At the same time, the operon model appeared.
