Coupled inheritance of signs. Analysis of the inheritance at the same time several signs in Drosophila, carried out by T. Morgana, showed that the results of the analyzing crossing of Fi hybrids sometimes differ from the expected in the case of their independent inheritance. The descendants of such crossing instead of free combination of signs of different pairs observed a tendency to inherit mainly parental combinations of signs. Such inheritance was named captured. The enclosed inheritance is explained by the location of the respective genes in the same chromosome. As part of the latter, they are transmitted from generation to generation of cells and organisms, while maintaining the combination of parent alleles.

The dependence of the adhesive inheritance of the signs from the localization of genes in one chromosome gives reason to consider chromosomes as separate clutch groups.

With the analyzing male crossing from F 1, only two types of descendants similar to parents appeared on a combination of options for analyzed signs (gray body color and normal wings or black body painting and short wings) in a 1: 1 ratio. This indicates the formation of males F 1 of the total of two types of weights with the same probability, in which the initial parent combinations of alleles of genes control the names (BV or BV) fall.

With analyzing the crossing of females F 1, four types of descendants appeared with all possible combinations of signs. At the same time, the descendants with parental combinations of signs met at 83%. At 17% of the descendants there were new combinations of signs (gray body painting and short wings or black body color and normal wings). It can be seen that in these crossings, the tendency to the lifting inheritance or dominant signs or recessive (83%) is manifested. A partial disruption of the clutch (17% of descendants) was explained by the crosslinker process - the exchange of relevant areas of homologous chromosomes in Profase I MEIOS (see Fig. 3.72).

From the results of the crossing, it follows that females of drosophila form four types of weights, most of which (83%) are increasing ((BV) and (BV)), 17% of the weights formed by them appear as a result of cross hinge and carry new combinations of alleles of the analyzed genes ((BV ) And (bv)). The differences observed in the crossing of males and females from F 1 with recessive homozygous partners are explained by the fact that for malfunctional reasons, the males drosophila does not cross crossing. As a result, male digeroosigons on genes located in one chromosome form two types of weights. In females, the cross hinge holds and leads to the formation of unknown and crossover games, two types of each. Therefore, four phenotypes appear in the offspring from the analyzing crossing, two of which are new compared to parents with combinations of signs.

Fig. 6.14. Coupled inheritance of signs

(body color and wings length of drosophila):

I.- Crossing clean lines, III -analyzing mappings and females from F 1.

Studying the inheritance of other characteristics of signs has shown that the percentage of crossover offspring for each pair of signs is always the same, but it differs for different pairs. This observation was the basis for the conclusion that genes in chromosomes are located in linear order. It was noted above that the chromosome is a group of clutch of certain genes. Homologous chromosomes are the same clutch groups that differ from each other. only Alleles of individual genes. In conjugation, homologues are brought together with their allelic genes, and when crossingrad, they exchange relevant areas. As a result, cross-level chromosomes appear with a new set of alleles. The frequency with which exchanges on the site between the two data genes depends on the distance between them (T. Morgan rule). The percentage of crossover Games, indirectly reflects the distance between genes. This distance is customary to express in santhmorganids. Over one centimorganide, the distance between the genes is taken, in which 1% of crossover offspring (crossover games) is formed.

With an increase in the distance between the genes, the likelihood of crossgrowth increases in the area between them in the precursor cells of the Games. Since two chromatids of four present in the Bivalent are involved in the crosslinker's act, even in the case of the exchange between the genes of this pair in all precursor cells, the percentage of cross-gel cells cannot exceed 50. However, this situation is possible only theoretically. Practically with an increase in distance between genes, the possibility of passing at the same time several crossings in this area (see Fig. 5.9). Since each second crossing leads to the restoration of the former combination of alleles in the chromosome, with increasing distance, the number of crossover games may not increase, but to decrease. It follows from this that the percentage of crossover gamets is an indicator of the true distance between genes only with a fairly close location, when the possibility of the second cross trigger is excluded.

Violation of the adhesive inheritance of parental alleles as a result of a crosslinker allows you to talk about incomplete clutch Unlike full clutch, Observed, for example, in males drosophila.

The use of an analyzing crossing in the experiments of T. Morgana showed that with it, it is possible to find out not only the composition of pairs of nonallerant genes, but also the nature of their joint inheritance. In the case of an adhesive inheritance of signs, according to the results of the analyzing crossing, you can also establish the distance between the genes in the chromosome.

Fig. 6.15. Scheme explaining the low percentage of cross-gaming

(in relation to two data genes)

Plus, the precursor cells are indicated, in which the crossingler passed on the site between the two data genes; Crossover gamets are burned

Genetic maps chromosomes - This is a diagram of a relative location and relative distances between genes of certain chromosomes located in one clutch group.

For the first time, T. Morgan and its staff indicate the possibility of building genetic maps of chromosomes. They experimentally showed that based on the adhesion phenomena of genes and cross hinge, you can build genetic maps of chromosomes. The possibility of mapping is based on the constancy of the percentage of crossfield between certain genes. Chromosome genetic maps are compiled for many types of organisms: insects (drosophila, mosquito, cockroach, etc.), mushrooms (yeast, aspergill), for bacteria and viruses.

Human genetic maps are used in medicine in the diagnosis of a number of serious hereditary human diseases. In the studies of the evolutionary process, genetic maps of different types of living organisms are compared.

As in other laws of heredity, in the law on the adhesion of genes immediately discovered exceptions. Morgan found in 1911 that in a homologous pair chromosoma regularly exchanges genes. In the crossing of organisms that differ in the pair of features, in F 1, the AV / AB digerogenotes are obtained. In the crossing of descendants F 1 with the parental form of AB / AB, in the case of a complete adhesion, the splitting of AB / AB and AB / AB would have obtained in the 1: 1 ratio. However, new combination of features always appear, for example, AB / AB and AB / AB. It means that, during gametogenesis, new grades were formed due to the crossroads of chromosomes and their fragments. T.ch. Morgan with employees crossed the Drozophil lines containing the genes A - Black Body, B - Effective Wings). Further, reciprocal crossing were set: in one digeterosigue was a female, and the diogomosigue - the male, in another crossing - on the contrary. If the digesterosigot was a male, in the offspring 1 part has a phenotype AB, the other part is AB. These classes are split in a 1: 1 ratio. In the reciprocal crossing, four classes of descendants were obtained, two of which have adhesive genes, in the order in which they were observed in their parents, and two other classes arose as a result of a clutch impairment - these are crossovers. These results are irrefutably showing that during the Gametogenesis, fragments of chromosomes - a crosslinker occurred. In each of the classes, the number of flies was in certain numerical ratings: AB / AB and AB / AB were 41.5%, i.e. Necrossors were 83%. Two sneakers in terms of individuals were also the same (8.5%) and their sum is 17%. The percentage of crossing counsel is defined as the ratio of the number of weights with registered exchanges between two specific pairs of alleles to the total number of weights. The value of the crosslinker between the two genes detected in the experiment can not be more than 50%, since This frequency is the probability of normal, i.e. Without crosslinker, discrepancies chromosomes.

Complete adhesion of genes. If the genes are located in the chromosome directly after each other, the crossingover between them is almost incredible. They are almost always inherited together, and when analyzing crossing, splitting in the ratio of 1: 1 is observed. Incomplete adhesion of genes. If the genes in chromosomes are located at some distance from each other, then the frequency of the crossover between them increases and, therefore, cross-board chromosomes that carry new combinations of genes are appear: AB and AB. Their number is directly proportional to the distance between the genes. In case of incomplete clutch, a certain number of cross-molds appear in the offspring, and their quantity depends on the distance between the genes. The percentage of cross-molds indicates the distance between the genes located in one chromosome.

Clutch group - A combination of genes in one chromosome. The number of clutch groups is equal to the number of pairs of homologous chromosomes of a given organism (in other words, it is equal to the haploid number of its chromosomes). For example, in the pea, the number of chromosomes 14 (2n \u003d 14, n \u003d 7), therefore, it has 7 clutch groups.

Genes located in one chromosome are clutch group. Clutch genes - This is a joint inheritance of genes located in the same chromosome. The number of clutch groups corresponds to the haploid number of chromosomes. The adhesion of genes located in one chromosome may be complete or incomplete. Full clutch: Morgan crossed black long-haired females with gray with the embossed wings of males. Drosophila has a gray color of the body dominates black, longness - above the stuffed wings. Gray body - a, black body A; Long-tempered - in, stuffed wings - in. Under spermgenesis during the period of MEIOS, homologous chromosomes are diverted into different genital cells. 1) AA // AV * AV // AV \u003d 4AV // AV; 2) AV // AV * AV // AV \u003d AB // AV, AV // AV, AV // AV, AV // AV. If the genes are in autosomes, then with full clutch in F1 will be uniformity according to the phenotype, and in F2 - 3: 1, mostly notes did not distinguish their parents, because One pair is studied by chromosomes.

Phenomenon of incomplete clutch in inheritance

As a result of crusting, the descendants had a combination of signs, like the initial parental forms, but there were individuals and with a new combination of signs - incomplete grip. B - gray, in - black, V - normal, V - the stuffed. Bv || bv * bv || bv \u003d bv || bv; The females from the first generation were crossed with males analyzers: bv // bv * bv // bv \u003d bv // bv, bv // bv is not cross-line. Bv // bv * bv // bv \u003d 2bv // bv, 2bv // bv - cross-line. The exchange of homologous chromosomes in its parts is called crossing or crosslinker. Individuals with new combinations of signs formed as a result of crosslinker, called crossovers.The amount of appearance of new forms depends on the frequency of the cross, which is determined by the following formula: the frequency of the intersection \u003d (number of cross-line forms) · 100 / total number of descendants. Over the unit of measurement of the cross, its value is made equal to 1%. It is called morgame. The magnitude of the crossing depends on the distance between the generic genes. The more genes are distant from each other, the more often there is a cross; The closer they are located, the probability of the cross is less.

Maps chromosomes. An example of their construction

Map chromosomes - Plan of the location of genes in the chromosome. The genes are located in chromosomes in a linear sequence at certain distances from each other. Phenomenon of crossing drivers in one section of the crosslinker on the other received the name interference. The smaller the distance separating the three genes, the greater the interference. Taking into account the linear arrangement of genes in the chromosome, taking the frequency of the crosslinch per unit of distance, Morgan was the first map of the generation of genes in one of the chromosomes of Drosophila: SH ___ 13.6 ___ y \u200b\u200b___ 28.2 ___ b. When constructing cards, not the distance between genes indicate, and the distance to each gene from the zero point of the beginning of the chromosome. The dominant allele is indicated by a capital letter, recessive - lowercase. After building genetic cards, the question arose that the location of genes in the chromosome, built on the basis of the crosslinker frequency, the true location. Each chromosome in length has specific disk patterns, which makes it possible to distinguish its different sections from each other. The material for testing was the chromosomes, in which various chromosomal restructuring occurred due to mutation: lacked individual disks, or they were inverted, or doubted. The physical distances between the genes on the genetic map do not quite correspond to the established cytological. However, this does not reduce the values \u200b\u200bof genetic maps chromosomes to predict the likelihood of features with new combinations of signs. Based on the analysis of the results of numerous experiments with Drosophilus T. Morgan, formulated chromosomal theory heredity, the essence of which is as follows: 1) genes are in chromosomes, they are located linearly at a certain distance from each other; 2) Genes located in one chromosome belong to one clutch group. The number of clutch groups corresponds to a haploid number of chromosomes; H) the signs whose genes are in the same chromosome, inherited; 4) In the offspring of heterozygous parents, new combinations of genes located in a single pair of chromosomes may arise as a result of crosslinker in the process of MEIOS. Crossing heer frequency depends on the distance between the genes; 5) Based on the linear arrangement of genes in chromosome and crosslinker frequency as an indicator of the distance between genes, you can build maps chromosomes.

Genes located in one chromosome are clutch group. Clutch genes - This is a joint inheritance of genes located in the same chromosome. The number of clutch groups corresponds to the haploid number of chromosomes. The adhesion of genes located in one chromosome may be complete or incomplete. Full clutch: Morgan crossed black long-haired females with gray with the embossed wings of males. Drosophila has a gray color of the body dominates black, longness - above the stuffed wings. Gray body - a, black body A; Long-tempered - in, stuffed wings - in. Under spermgenesis during the period of MEIOS, homologous chromosomes are diverted into different genital cells. 1) AA // AV * AV // AV \u003d 4AV // AV; 2) AV // AV * AV // AV \u003d AB // AV, AV // AV, AV // AV, AV // AV. If the genes are in autosomes, then with full clutch in F1 will be uniformity according to the phenotype, and in F2 - 3: 1, mostly notes did not distinguish their parents, because One pair is studied by chromosomes.

Phenomenon of incomplete clutch in inheritance

As a result of crusting, the descendants had a combination of signs, like the initial parental forms, but there were individuals and with a new combination of signs - incomplete grip. B - gray, in - black, V - normal, V - the stuffed. Bv || bv * bv || bv \u003d bv || bv; The females from the first generation were crossed with males analyzers: bv // bv * bv // bv \u003d bv // bv, bv // bv is not cross-line. Bv // bv * bv // bv \u003d 2bv // bv, 2bv // bv - cross-line. The exchange of homologous chromosomes in its parts is called crossing or crosslinker. Individuals with new combinations of signs formed as a result of crosslinker, called crossovers.The amount of appearance of new forms depends on the frequency of the cross, which is determined by the following formula: the frequency of the intersection \u003d (number of cross-line forms) · 100 / total number of descendants. Over the unit of measurement of the cross, its value is made equal to 1%. It is called morgame. The magnitude of the crossing depends on the distance between the generic genes. The more genes are distant from each other, the more often there is a cross; The closer they are located, the probability of the cross is less.

Maps chromosomes. An example of their construction

Map chromosomes - Plan of the location of genes in the chromosome. The genes are located in chromosomes in a linear sequence at certain distances from each other. Phenomenon of crossing drivers in one section of the crosslinker on the other received the name interference. The smaller the distance separating the three genes, the greater the interference. Taking into account the linear arrangement of genes in the chromosome, taking the frequency of the crosslinch per unit of distance, Morgan was the first map of the generation of genes in one of the chromosomes of Drosophila: SH ___ 13.6 ___ y \u200b\u200b___ 28.2 ___ b. When constructing cards, not the distance between genes indicate, and the distance to each gene from the zero point of the beginning of the chromosome. The dominant allele is indicated by a capital letter, recessive - lowercase. After building genetic cards, the question arose that the location of genes in the chromosome, built on the basis of the crosslinker frequency, the true location. Each chromosome in length has specific disk patterns, which makes it possible to distinguish its different sections from each other. The material for testing was the chromosomes, in which various chromosomal restructuring occurred due to mutation: lacked individual disks, or they were inverted, or doubted. The physical distances between the genes on the genetic map do not quite correspond to the established cytological. However, this does not reduce the values \u200b\u200bof genetic maps chromosomes to predict the likelihood of features with new combinations of signs. Based on the analysis of the results of numerous experiments with Drosophilus T. Morgan, formulated chromosomal theory heredity, the essence of which is as follows: 1) genes are in chromosomes, they are located linearly at a certain distance from each other; 2) Genes located in one chromosome belong to one clutch group. The number of clutch groups corresponds to a haploid number of chromosomes; H) the signs whose genes are in the same chromosome, inherited; 4) In the offspring of heterozygous parents, new combinations of genes located in a single pair of chromosomes may arise as a result of crosslinker in the process of MEIOS. Crossing heer frequency depends on the distance between the genes; 5) Based on the linear arrangement of genes in chromosome and crosslinker frequency as an indicator of the distance between genes, you can build maps chromosomes.

Bisexuality, intersexuality, hyanderomorphism, churmerism in sex chromium mothers. The role of hormones and environmental conditions in developed

Any zygota has X-chrome and autosomes, i.e. Has genes and female and male, i.e. Genetically any organism bisexual(bisexual). Intersexes - Heroofrodites are individuals with developed and female and male signs. 2 types: True - have female and men's sexes due to violation of gene balance; Conditional - have glands of one sex, and the outer sexual sign of the other sex due to the violation of the hormone balance. Sometimes insects and animals meet hyanderomorphs - One part of the body has female signs, and the other is men. Causes: Female's zygota is divided into 2 blastomer. One of them lost one x-chrome. From this blastomer will develop men's half body. Chimerism Half chromosomes of XX / HU occurs in multiple animals, in bulls - when in the same body contains the XH-chromosome, and the reproduction of the hubromosoma is broken. In conventional feeding, males grow up, and if you add women's sex hormones in the feed, female grow (Fish Fish). If the larva of the sea worm attaches to the bottom of the sea - the female, if the female truth is the male.

Types of floor determination in animals. Primary and secondary floors. Floor regulation problem

Determination Provides the formation of equal number of males and females, which is necessary for normal self-reproduction of the species. Types: 1) Epigamic - the floor of the individual is determined in the process of ontogenesis, depends on the external environment. 2) Proginated - the floor is determined during the Gametogensis of the individuals of the individual. 3) Singham - the floor is defined at the time of the merge merges. Primary and secondary floors:the ratio of floors, the cat is determined at the time of the merge of Games, Naz-Sm primary, always 1: 1. Any change in the ratio of floors, both before and after birth, Naz-Xia secondary. Usually after birth, it shifts in favor of the female, so many species of animals and man-ka male features are born more than women's: rabbits - 57%, people - 51%, birds - 59%. Floor control problem:it has an important economic significance. Nr: In dairy cattle breeding, in egg poultry, females are desirable, and where the main product is meat, better males. The problem is to divide the sperm on the X- and the Fraction. Ways: 1) Electrophoresis - x - sperm have a negative charge - move to the cathode, and y - sperm - to the anode. Guarantee 80%. 2) The deposition method - X - the sperm is more dense and falls down, and y - remains on top. 3) the use of a kit of acids to change the pH of the female sex tract to create conditions only for x - or only for u-. 4) Parthenogenesis: Genogen - receiving females - x-ray rays irradiated ovocit. First order, thereby detain the discrepancy to chrom-m, the image-smiling egg with a diploid set of chromons, a female develops without fertilization. Androgenesis - the production of males - the egg core is killed by the rays of the X-ray, then two sperm penetrate into it, the kernels merge, giving a diploid set, the male. 5) Method of separation of sperm on fractions by number of DNA in sperms. 6) Than younger parents, the probability of their male is more. 7) The more sperm in the female female, the most likely the birth of male. 8) The greater the sperm is stored. 9) Bird feeding: if the rooster in the feed is added, then the female, and if to - males. 10) In any population there is an equilibrium law, i.e. The ratio of floors seeks 1: 1.

The mechanism of inheritance of adhesive genes, as well as the location of some clutch genes, installed the American genetic and embryologist T. Morgan. He showed that the law of an independent inheritance, formulated by Mendel, is valid only in cases where genes carrying independent signs are localized in different non-homologous chromosomes. If the genes are in the same chromosome, the inheritance of the signs takes place together, that is, adhesive. This phenomenon began to be called clutch inheritance, as well as the law of clutch or the law of Morgan.

The law of clutch reads: Coupled genes located in one chromosome are inherited together (captured). Clutch group - All genes of one chromosome. The number of clutch groups is equal to the number of chromosomes in the haploid set. For example, a person has 46 chromosomes - 23 clutch groups, in pea 14 chromosomes - 7 clutch groups, in fruit flour fruit 8 chromosomes - 4 clutch groups. Incomplete grip of genes - the result of the crossfield between the clutch genes, so full grip of genes Perhaps the organisms in the cells of which the cross hinge does not normally occur.

Chromosomal Morgan's theory. Basic provisions.

The result of T. Morgan's research was the creation of a chromosomal theory of heredity:

1) genes are located in chromosomes; Various chromosomes contain an unequal number of genes; The set of genes of each of the non-homologous chromosomes is unique;

2) each gene has a certain place (locus) in the chromosome; In identical locus, homologous chromosomes are allelic genes;

3) genes are located in chromosomes in a certain linear sequence;

4) genes localized in one chromosome are inherited together by forming a clutch group; The number of clutch groups is equal to the haploid set of chromosomes and constantly for each type of organisms;

5) the adhesion of genes can be disturbed in the crosslinker process, which leads to the formation of recombinant chromosomes; The crosslinker frequency depends on the distance between the genes: the greater the distance, the greater the grade of the crosslinker;

6) Each species has a set of chromosomes characteristic only for it - karyotype.

Inheritance adhesive with floor - This is the inheritance of any gene located in the genital chromosomes. In heredity associated with Y-chromosome, a sign or illness manifests itself exclusively in a man, since this sex chromosome is absent in a chromosomal set of women. The heredity associated with the X-chromosome may be dominant or recessive in the female body, but it is always present in male, since it consists of only one X chromosome. The inheritance of the disease adhesive with the floor, is mainly mainly with sexual x-chromosome. Most of the hereditary diseases (certain pathological signs) associated with the floor are transmitted recessively. There are about 100 such diseases. The female of the pathological sign itself does not suffer, since the healthy X-chromosome dominates and suppresses the X-chromosoma with a pathological basis, i.e. Compensates the inferiority of this chromosome. At the same time, the disease is manifested only in male people. According to the recessive clutch with the X-chromosome type, transmitted: Daltonism (red-green blindness), atrophy of the visual nerves, chicken blindness, myopia Duceda, the Curly Hair Syndrome (arises as a result of the violation of copper exchange, increase its content in tissues, manifested by the weak-colored , rare and drop-down hair, mental retardation, etc.), the defect of the enzymes by transferring purine bases in nucleotides (accompanied by a disorder of DNA synthesis in the form of Lesha-Nayn syndrome, manifested by mental retardation, aggressive behavior, self-esteem), hemophilia A (as a result of a lack of Antihemophilic globulin - factor VIII), hemophilia in (as a result of the deficit of the Christmas factor - Factor IX), etc. A hypophosphatemic rickets (non-treated with vitamins D2 and D3), brown enamel of teeth, etc., are transmitted to the dominant adhesive with X-chromosome type (non-treated with vitamins D2 and D3). These diseases develop in people and male and female.

Full and incomplete adhesion of genes.

Genes in chromosomes have a different clutch power. The adhesion of genes can be: complete, if between genes belonging to one clutch group, recombination is impossible and incomplete, if between genes belonging to one clutch group, recombination is possible.

Chromosome genetic maps.

These are the schemes of the relative location of the adhesive

hereditary factors - genes. G. K. X. Display real

existing linear procedure for placing genes in chromosomes (see Cytological maps of chromosomes) and are important both in theoretical studies and during breeding work, because Allowed to consciously pick up a couple of signs in crossings, as well as to predict the features of inheritance and manifestations of various signs among studied organisms. Having G. K. X., It is possible to inherit the "signal" gene, closely linked with the studied, control the transmission of genes to the offspring, due to the development of difficult analyzed signs; For example, a gene defining endosperm in corn and located in the 9th chromosome, adhesion with a gene that determines the reduced viability of the plant.

85. Chromosomal floor inheritance mechanism. Citogenetic floor definition methods.

Floor It is characterized by a complex of features determined by genes located in chromosomes. At species with separate individuals, the chromosomal complex of males and females of unequal, cytologically, they differ in one pair of chromosomes, it was called semi chromosomes. The same chromosomes of this pair called X (X) - chromosomes . Unpaired, missing Y (igrek) - chromosome ; the rest for which there is no difference autosomas (BUT). Human has 23 pairs of chromosomes. Of them 22 pairs of autosomes and 1 pair of sex chromosomes. The floor with the same XX chromosomes forming one type of weights (with X-chromosome) is called homogaten another floor, with different XY chromosomes, forming two types of weights (with X-chromosome and with Y-chromosome), - heterogamate. In humans, mammals and other organisms men's heterogament floor; In birds, butterflies - female.

X-chromosomes, in addition to genes defining female, contain genes that are not related to the floor. Signs defined by chromosomes are called signs lucked with floor. A person has such signs of daltonism (color blindness) and hemophilia (non-blank blood). These anomalies are recessive, women such signs do not appear if even these genes carry one of the X-chromosomes; Such a woman is a carrier and transmits them with x - chromosome to her sons.

Citogenetic floor definition method. It is based on a microscopic study by chromosomes in human cells. The use of the cyto of the genetic method allows not only to study the normal morphology of chromosomes and the karyotype as a whole, to determine the genetic floor of the body, but the main thing is to diagnose various chromosomal diseases associated with a change in the number of chromosomes or with a violation of their structure. As an express method that detects a change in the number of sex chromosomes is used the method of determining sex chromatinin the underwent cells of the mucous membrane of the cheek. Sex chromatin, or Barra Taurus, is formed in the cells of the female organism of one of the two x-chromosomes. With an increase in the amount of X-chromosoma in the karyotype of the body in its cells, Barra should be formed in an amount per unit less than the chromosome number. With a decrease in the number of chromosomes, there is no taurus. In the male karyotype of the Y-chromosome, it can be detected by more intensive lumisement compared to other chromosomes when processing their acrycinite and study in ultraviolet light.

Features of the structure of chromosomes. Levels of organization of hereditary material. Hetero- and Eukhromatin.

Morphology chromosomes

With microscopic analysis of chromosomes, first of all, the differences in form and magnitude are visible. The structure of each chromosome is purely individual. It can also be seen that chromosomes have common morphological signs. They consist of two threads - chromatide Located in parallel and interconnected at one point, called the centromer or the primary drawing. On some chromosomes, you can see a secondary lagging. It is a characteristic feature that allows you to identify individual chromosomes in the cell. If the secondary hauling is located close to the end of the chromosome, then the distal plot limited by it is called the satellite. Chromosomes containing satellite are indicated as at-chromosome. On some of them, the formation of nucleols occurs in the elegase.
The terminal sections of chromosomes have a special structure and are called telomeres. Teomeric areas have a certain polarity that prevents them with compound with each other during ruptures or with free chromosomes.

The sector of chromatide (chromosome) from telomeres to centromers is called the shoulder of chromosome. Each chromosome has two shoulders. Depending on the ratio of the shoulders, three types of chromosomes are isolated: 1) meticenteric (equal injuries); 2) submetrical (inequalization); 3) Acrocentric, who have one shoulder very short and not always clearly distinguishable. (P - short shoulder, q - long shoulder). The study of a chemical organization of chromosomes of eukaryotic cells showed that they consist mainly of DNA and proteins: histones and protubette (in sex cells), which form a nucleoprotein complex-chromatin, which received its name for the ability to be painted with major dyes. Proteins make up a significant part of the chromosoma substance. They account for about 65% of the mass of these structures. All chromosomal proteins are divided into two groups: Histons and non-regional proteins.
Histons Present five fractions: Hi, H2A, H2B, NH, H4. As a positively charged basic proteins, they are strongly connected to DNA molecules, which prevent the reading of biological information into it. This is the regulatory role. In addition, these proteins perform a structural function, providing a spatial organization of DNA in chromosomes.

Number of fractions nonregistone Proteins exceed 100. Among them, enzymes of synthesis and RNA processing, Reducing and DNA reparations. Chromosome acidic proteins also perform a structural and regulatory role. In addition to DNA and proteins, RNA, lipids, polysaccharides, metal ions are also found in chromosomes.