Heredity

Heredity is a biological phenomenon, which consists in the manifestation of similar morphological and functional characteristics in successive generations. Heredity is due to hereditary factors (genes) and is divided into nuclear cytoplasmic (viadero) and acaricides characteristic of bacteria and viruses that do not have a core characteristic of higher organisms. Thin experiments with changes and destruction of the nuclei of eggs, it was shown that the morphological and functional continuity between generations is provided with all self-replicating structures cells: nuclear and cytoplasmic (sniadanie), but the kernel - or rather, its constituent of the chromosomes (see) are the main carriers of hereditary information. The constant transmission of signs is provided by the identical reproduction of the genetic material during cell division (see Mitosis). Human organism develops from a single fertilised egg, in which one half of the chromosomes presents from the father and the other from the mother. Chromosomes contain deoxyribonucleic acid, abbreviated DNA (see Nucleic acid), which linked the preservation and transmission of genetic information from generation to generation. Each gene is a certain site (locus) DNA molecules and contains an average of several hundred nucleotides (single nucleotide - mononukleotid - consists of phosphoric acid, desoxyribose and purine or pyrimidine bases), the combination of which determine the specificity of a particular gene. Playback of genes associated with the ability of DNA to a doubling of the use of specific proteins-enzymesthat provides the transmission of hereditary information from parent cell to the child. This ability genes to reproduce themselves in the process of cell division is the basis of the mechanism of heredity. The process of realization of genetic information stored on DNA, is divided into two phases: transcription and translation. Transcription is a first step of realization of genetic information - "withdrawal" of its DNA, and the translation of a nucleotide sequence of the DNA molecule in the amino acid sequence of a protein molecule is called broadcasting. The position of each triplet of nucleotides (a triplet) in the DNA molecule determines the place of incorporation of amino acids in the protein molecule that takes place with the participation of ribonucleic acids, abbreviated RNA (see Nucleic acid). Schematically genetic information is as follows: on the nuclear DNA, as in the matrix, is synthesized a molecule of messenger RNA (RNA) - the transcription process; and-RNA then enters the cytoplasm, where it "strung" ribosomes, consisting of ribosomal RNA (ednonachalie) and protein. Another type of ribonucleic acid - transfer RNA (t-RNA) is delivered to the ribosome amino acids, each of which is located in strict compliance with the sequence of triplets and-RNA,the process of translation. For each amino acid has "its own" corresponding t-RNA. After activation of amino acids under construction in the protein chain t-RNA are released and can once again take part in the transport of amino acids to the ribosome and the "Assembly" of new protein molecules. Under the control of genes from 20 currently known amino acids are formed of different proteins of the body.
In the cells which make up the tissues and organs of a person (with the exception of sex), are identical chromosomes and genes, but the structure and function of cells differ greatly even within the same body. This is because in developing tissues is included in the action of one and the termination of the activity of other genes. Under genetic control cells develop in different directions, which leads to the formation of different tissues and organs. Each gene acts on a certain stage of development and in particular cellular system. With the development of the embryo , a growing number of genes shows his activity and engaging in various kinds of interaction contributes to the weakening or strengthening controlled by them features. Is often the suppression of activity of a gene or the conditions impeding the inclusion of it in action. The interaction of different genes leads to that effect (the result of) the same gene varies greatly, i.e. gene has a different expression (pronounced action). Some genes control the appearance of only one sign, while the other leads to multiple effects (pleiotropy). The latter may be related to controlling the genome of the development of any single bookmark from which later formed the different organs. Pleiotropy may occur as a result of the fact that genes acting in any one cell system are responsible for the synthesis products, affecting the development of other bodies.
Genes are located on chromosomes in a linear order. If in the same loci pairs of chromosomes are the same alleles (i.e. alternative forms of genes that control the same manifestations of the sign, then this state is called homozygous, and if it is different, heterozygous. In the case of homozygosity equivalent genes affect the occurrence of any character. In the case of heterozygosity one of allelic gene suppresses the effects of another. More "strong" gene called dominant, and depressed - recessive. The effects of the dominant genes relatively easily detected, and the transfer of genes themselves not difficult to trace in a few generations. In contrast, the transfer of the offspring of recessive genes to identify much more difficult, especially in small families.
Along with dominant and recessive mode of inheritance occurs co-dominant inheritance, when heterozygous organism are shown the effects of both alleles. Codominant often found in the synthesis of antigens of blood. In addition, the expression of conditions for growth, weight, body shape, and others, due to cumulative effects of many genes. Such genes, forming a polygenic system, individually give a weak effect, but their cumulative effect is quite strong.
Under the influence of external factors, such as ionizing radiation, chemical and biochemical processes in the cell, in the hereditary substance may cause various changes, such as substitution of one nucleotide others, who due to the nature of the genetic material can be transmitted to subsequent generations of somatic cells, either, originating in gametes, offspring of a given organism, i.e. mutations occur (see Variability).
The combination of all localized to chromosome genes is the genotype, and the combination of all hereditary characteristics of the organism - the phenotype. Often the term ' gene ' is used in relation to one or several pairs of genes and phenotype is accordingly called controlled by those genes signs.
Heredity plays a significant role in the emergence of many common diseases: atherosclerosis, hypertension, diabetes and other Knowledge of the mechanisms of realization of genetic information and conditions influencing its manifestation, now makes it possible to treat and prevent a number of hereditary diseases.
Cm. also, Genetics, genetic diseases.

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Azernikov Century 3. A transcript of life. 10 l. so 24200, price 34 kopecks
Every moment in our body die thousands of old cells and are born thousands of new.
Between birth and death of the cell lives, synthesizes proteins. Protein - hundreds of thousands; building substances, of which creates their cage, only twenty species. How is leading the cell is a unique construction, as manages do not mix in their jewelry work? These and many other questions will be answered book.
Recently, scientists have made an important discovery. It turned out that cell life, her work is pre-programmed. The program is written in the form of a special chemical cipher on molecules of deoxyribonucleic acid - DNA, are located on chromosomes in the cells. Cipher built by the alternation of four nuclear bricks that make up the DNA molecule.
The secret cipher inheritance opens before science enormous opportunities. Reading this cipher, you can try to change it, change the hereditary instructions of the body. This will help to struggle with many hereditary diseases, cancer, prospects of creation of the fruit of great weight and sugar content, will allow better prevent premature aging of the body.
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