In 1909, the Belgian cytologist Janssen was observed the formation of chiam during proofased I MEIOS. The genetic significance of this process explained Morgan, expressed the opinion that the crossingover (exchanging alleles) occurs as a result of the gap and recombination of homologous chromosomes during the formation of chicas. At this time, the parts of two chromosomes can crossed and share their sections. As a result, qualitatively new chromosomes, containing sites (genes) both maternal and father chromosomes, arise. Alleles included in the clutch groups in parental individuals are separated and new combinations are formed, which fall into gametes - the process, called genetic recombination. Descendants that are obtained from such heams with "new" combinations of alleles are called recombinant.
The frequency (percentage) of the crossroads between two genes located in one chromosome is proportional to the distance between them. The crossover between the two genes occurs, the less often, the closer to each other they are located. As the distance between the genes increases, the likelihood that the crosslinker raises them in two different homologous chromosomes is increasing.
The hybrids of the first generation (females) were crossed with the black-walled infancy males. In F2, in addition to parent combinations of signs, new - flies with black bodies and stairous wings, as well as with gray body and normal wings. True, the number of recombinant descendants is small and is 17%, and parental - 83%. The reason for the appearance of a small amount of flies with new combinations of signs is a crosslinker, which leads to a new recombinant combination of alleles of B + and VG genes in homologous chromosomes. These exchanges occur with a probability of 17% and ultimately give two class of recombinants with an equal probability - 8.5%.
The biological importance of the crossing agener is extremely large, since genetic recombination allows you to create new, previously not existing combinations of genes and thereby increase the hereditary variability, which provides ample opportunities to adapt the body in various environments.
Mutagena and Testing them
Mutagen - physical and chemical factors that the impact of which is alive
organisms cause changes in hereditary properties (genotype). Mutagena
we are divided into: physical (X-ray and gamma rays. Radionuclides,
protons, neutrons, etc.), physico-chemical (fiber, asbestos), chemical
(pesticides, mineral fertilizers, heavy metals and etc.). biological
(Some viruses, bacteria).
Testing for mutagenicity. Strategy Testing on mutagenicity. To test all substances with which, throughout the life, a person can contact, it would be necessary to exorcilely a large amount of work, so the need for priority test for the mutagenicity of drugs was recognized, food additives, pesticides, herbicides, insecticides, cosmetic products, the most widespread water and air pollutants, as well as production hazards. The second methodological principle consists in selective testing. This means that the substance is analyzed by mutagenity in the presence of two mandatory conditions: prevalence in human habitat and the presence of structural similarities with known mutagenes or carcinogens. The absence of a universal test that allows you to simultaneously register the induction with the studied substance (and its possible metabolites) of various categories of mutations in the genital and somatic cells, serves as the basis of the third principle - the integrated use of specialized test systems. Finally, the fourth methodological principle implies the step of testing of substances on mutagenic activity. This principle originates from one of the first and most well-known schemes proposed in 1973 b, Bridgez and providing for three consecutive stages of the study. 1. At the first stage, the mutagenic properties of the substance were studied by simple and rapidly performed methods (using microorganisms and drosophila as test objects) to determine its ability to induce gene mutations. The identification of such ability was assumed a ban on the use of this substance. 2. In the case of a special medical or economic significance of Mutagena, it was tested on mammals in vivo. A similar study was also conducted for substances that did not demonstrate mutagenic properties in the tests of the first stage. If the agent studied did not show mutagenic properties, the safety of the use of his person was postulated. Substances that showered mutagenicity or prohibited for use, or if they treated the category of particularly significant, or irreplaceable, were investigated additionally. 3. At the final stage, testing was carried out to establish the quantitative patterns of mutagenic effects of such specific substances and the risk assessment of their use. This scheme served as a prototype of a number of integrated testing techniques for mutagenicity. In a fundamentally new step towards the development of this area should be considered the program proposed in 1996 by J. Eshby with co-authors, an extremely important feature of this program is its focus not only to evaluate the mutaging of the test substance, but also on the forecast of carcinogenicity of this chemical compound and the possible mechanism of carcinogenesis. A modern system of evidence of the relationship between mutagenesis and carcinogenesis processes includes a number of experimental confirmations of the problem under discussion. Among them: 1) the presence of well-studied hereditary diseases in which at the same time increased sensitivity A multiple excess of the average frequency of malignant neoplasms is observed to the action of Mutagens; 2) a clearly established conjugation of mutagenic and carcinogenic action of antitumor cytostatics induced mutations in somatic cells and due to this therapeutic effects that can cause the development of secondary tumors from treated oncological patients; 3) accumulated information on the possible activation of proto-curves due to the induction of gene and chromosomal mutations; 4) Description of cases of sporadic monogenic dominant mutations caused by the development of tumors of various organs. The J. ESHBI program is postulated that the substance is not a carcinogen if it does not show mutagenic and genotoxic effect in vivo. The same substances named effects are peculiar to potential genotoxic carcinogens.
Ticket 6.
Cytological evidence of Stern experiments. Paint.
Experience Stern.k x-chromosome was added a fragment of the U-chromosome, and she received a M-shaped form. At the beginning of the 1930s, K. Stern received the Lines of Drosophila, having sex chromosomes, distinguishable from each other at the cytological level. The female on one of the X-chromosomes was transferred a small fragment Y-chromosome, which gave it a specific M-shaped form, easily distinguishable under a microscope
The scheme of experience in cytological proof of crossfielder onD. Melanogaster
Females were obtained, heterozygous in two specified morphologically different X-chromosomes and at the same time in two genes VAG (B) and cARNATION (CAR).
Cytological analysis of 374 drugs of females showed that in 369 cases, the karyotype corresponded to the expected. All four classes of females had one normal, i.e. Holrom-shaped X chromosome received from the Father. Crossover (i.e. In sag + according to the phenotype), females contained a biscuit M-shaped X-chromosome.
Determination of lethal recessive mutations (methodCBL and Meller 5)
Flowing genes - causing fatal outcome in a homozygous state. Along with them, a large number of semi-dollar factors are known, leading very often to the birth of various kinds of non-visual freaks or simply in one way or another method of organisms reflected on the viability. In the present, the time of L. G. is known in Drosophila, mice, rabbits, dogs, pigs, sheep, horses, cattle, birds, in a number of plants, in humans, etc. An example of a half-dollar factor in a person can serve hemophilia, with The presence of which instead of normal blood coagulation in 5-5x / 2 minutes. This process is sometimes tightened to 120 minutes. and even more; The lethal hemophilia gene is localized in the sex chromosome, which explains the transfer of this sign by half the sons from the externally healthy mother, which is a heterozygous for this factor
The most convenient methods of mutation metering are designed for drosophila. Actually, it was the creation of methods for taking recessive lethal mutations in the X-chromosome determined the success of Mellor, who opened the effect of X-rays on the mutation process in Drosophila. To take into account recessive lethal mutations, linked with the floor, the Meller-5 method is widely used in the drosophila. The female line Meller-5, or M-5, is carried in both x-chromosomes in two inversion: SC 8 and Sigma49. Inversion SC 8 captures almost the entire X-chromosome, and within its limits there is another inversion -Sigma49. In this system, the cross hinge is completely suppressed. Inversion used do not have a recessive death. In addition, both chromosomes M-5 carry three markers: two recessive - W a (an apricot eye color) and SC 8 (shortened bristles-phenotypic manifestation of the inversion of the same name, affecting the SC gene) and one dominant - BAR. When crossing the studied males with females M-5 in individual families F 2 receive two classes of females and males, if there was no recessive lethal mutation in the X-chromosome of spermatozoa of the original male. If recessive lethal appeared, then in the appropriate individual culture in F 2 we will receive only one class of males, there will be no males wild type W + B +. Metleler-5 method can also be used to register recessive mutations in the X-chromosome with a visible manifestation. For this purpose, it is convenient to apply the Double Yellow method based on the crossing of the studied males with females that carry the linked x-chromosomes. Due to the fact that with such a crossing of the sons, they receive their X-chromosome directly from the father, recessive mutations in this chromosome can be considered already in F 1. Accounting for deaths and mutations with visible phenotypic manifestations is easier for x-chromosome Drozophila due to the specifics of its inheritance. However, there are methods for accounting for lethal mutations in autosomes. For example, to account for recessive lethal mutations in chromosome 2 use the so-called method of balanced flying. To do this, the line is used, heterozygous by chromosome 2. In one homologist there are dominant genes Cyrly (CY-curved wings) and LOBE (L- reduction of the eye of the blade form), in another PLUM homologist (PM-drain-brown eyes). In addition, chromosoma Su l contains inversions that are seen by the crossing race. All three dominant mutations have a recessive lethal action. Due to this, during the dilution of such a line, only heterozyges on the specified genes are survived. This is a system of balanced flying. To study recessive lethal mutations, as well as recessive mutations with a visible manifestation of the studied flies, cross with CYL / PM flies. In F 1, flies, heterozygous for one or another chromosome of the test line, and individually again cross CYL segregants with CYL / PM flies. In F 2, they cross the males and females with signs of CYL and analyzed F 3. In the absence of a recessive lethal mutation, the splitting F 3 will be 2CYL: 1CY + L +, and if death mutations arose in the genital cells of the source line, then in the respective individual cultures in F 3 there will be no normal flies of 2CYL: 0CY + L +. Similarly, take into account in F 3 and recessive mutations with a visible manifestation in chromosome 2.
Ticket 7.
Combinative variability and its value.
Combinative call variability, which is based on the formation of recombination, i.e. Such combinations of genes that did not have parents.
Based on combinative variability lies sexual reproduction Organizations, due to which there is a huge variety of genotypes. Practically unlimited sources of genetic variability serve three processes:
Independent discrepancy between homologous chromosomes in the first meiotic division. It is the independent combination of chromosomes during meyosis is the basis of the third law of Mendel. The appearance of green smooth and yellow wrinkled pea seeds in the second generation from crossing plants with yellow smooth and green wrinkled seeds is an example of combinative variability.
Mutual exchange of areas of homologous chromosomes, or crosslinker. It creates new clutch groups, i.e. It serves as an important source of the genetic recombination of alleles. Recombinant chromosomes, being in the zygote, contribute to the emergence of signs atypical for each of the parents.
Random combination of weights for fertilization.
These sources of combinative variability act independently and at the same time, while ensuring the permanent "shuffling" of genes, which leads to the emergence of organisms with other genotype and the phenotype (the genes themselves do not change). However, new combinations of genes are fairly easily disintegrated when transferring from generation to generation.
Sources:
Crossingringer during meyosis (homologous chromosomes are closely close and changed areas). Crossingrigner occurs at the beginning of MEIOS, when homologous chromosomes are built up against each other. At the same time, the areas of homologous chromosomes are crossed, come off, and then re-join, but already to another chromosome. In the end, four chromosomes are formed with different combinations of genes. Chromosomes, called "recombinant", carry new combinations of genes (AB and AB), absent in the initial chromosomes (AB and AB) - an independent discrepancy between chromosomes during meyosis (each pair of homologous chromosomes diverges regardless of other pairs). - Random fusion of heats for fertilization.
Combinative variability is an essential source of all colossal hereditary diversity characteristic of living organisms. However, the listed sources of variability do not generate essential for the survival of stable changes in the genotype, which are necessary, according to evolutionary theory, for the occurrence of new species. Such changes arise as a result of mutations.
The combinative variability explains why children discover new combinations of signs of relatives on maternal and paternal lines, and in such specific versions that were not peculiar to any father, nor mother nor grandfather or grandmother, etc. Thanks to combinative variability, a variety of genotypes are created in the offspring, which is of great importance for the evolutionary process due to the fact that: 1) increases the variety of material for the evolutionary process without reducing the viability of individuals; 2) the possibilities of adapting organisms to changing environmental conditions are expanding and thereby ensuring the survival of a group of organisms (populations, species) as a whole. The combinative variability is used in selection in order to obtain a more valuable in the economic attitude of the combination of hereditary signs. In particular, the phenomenon of heterosis is used, increasing the viability, growth intensity and other indicators in hybridization between representatives of various subspecies or varieties. It is pronounced, for example, corn (Fig. 78), which causes a significant economic effect. The opposite effect gives the phenomenon of inbreeding or closely related crossing - crossing organisms that have common ancestors. The generality of the origin of the crossed organisms increases the likelihood of the presence of the same alleles of any genes, and therefore the likelihood of homozygous organisms. The greatest degree of inbreeding is achieved in self-pollution in plants and self-exploitation in animals. Homozigity increases the possibility of manifestation of recessive allel GenovThe mutagenic changes of which lead to the emergence of organisms with hereditary anomalies. The results of the study of the phenomenon of combinative variability are used in medical and genetic counseling, especially at its second and third stages: the proceedings forecast, the formation of the conclusion and explanation of the meaning of genetic risk. In advising future marital couples, it is used to establish the likelihood of the presence of alleles obtained from the overall ancestor and identical by origin. To do this, use the coefficient of kinship expressed in the shares of the unit. At monosigitious twins, it is 1, among parents and children, brothers and sisters - 1/2, Santa and grandson, uncle and nephew - 1/4, at cousins \u200b\u200b(brothers and sisters) - 1/8, in secondary sibs - - 1/32, etc.
Examples: The flower has a night beauty there is a gene of red petals a, and white-colored gene. The organism AA has pink color of petals. Thus, the night beauty does not have a pink gene gene, a pink color occurs when a combination of red and white gene combinations.
A person has a hereditary sickle culmination anemia. AA - norm, aa - death, aa - ska. With SKA, a person cannot transfer increased physical exertion, while he does not ill malaria, i.e. The malaria pathogen malaria plasmodium cannot be powered by the wrong hemoglobin. Such a sign is useful in the equatorial belt; For him there is no gene, it occurs when the genes of genes A and a.
Types of non-allena interactions: epistasis dominant and recessive
Nonalleretic genes - These are genes located in various sections of chromosomes and encoding unequal proteins. Nonallean genes can also interact with each other.
At the same time, either one gene determines the development of several signs, or, on the contrary, one sign is manifested under the action of a set of several genes. There are three forms and interactions of non-allelegen genes:
-
Who will be a master? ..
Bachelor - Received bachelorism, 1st degree in foreign universities.
master - Chapter and Elder of some military-spiritual orders or fraternities;
The Master's degree, the average between the doctoral and candidate.Of Intelligent dictionary living Great Russian Language V.Daly
Preparatory stage
The game is held according to the scenario, similar to the scenarios of the teleigher "Who wants to become a millionaire?" And "Oh, lucky!".
Students in advance (for 2-3 lessons) the theme of the game is reported, the material is indicated, which must be repeated, the necessary literature is provided. Each participant of the game should prepare 4 cards with letters A, B, B, G (recommended size of cards: 15 x 15 cm). From the composition of students, 2-3 assistants of the lead (members of the Accounts Commission) are appointed, as a teacher and high school students can act as a teacher.
The class is in advance for 4-5 groups for conducting a qualifying round (the teacher brings to their information that in controversial situations leading will be guided tutorial rating Students).Rules of the game
The game consists of two rounds: qualifying and main. Begins the game presenter.
In the qualifying round, work is carried out in groups. The assistants are distributed in groups in advance prepared sheets in which it is necessary to place the letters in the correct sequence. The team that previously gives the right answers (or the most correct answers), plays mostly round.
To play mostly round, the team chooses a student from its composition, which will answer the questions of the lead. If the team has difficulty, the final decision takes either a leader or teacher.
Mostly round the player must be answered by 10 questions, of which the first 5 are simpler than the rest. Questions include basic concepts, terms, facts from the material passed.
Having answered 5 questions, the student receives the first "non-aggravated" title "Bachelor" of science, a certain game of the game. In the case of a general loss, this title remains behind the player (in the estimated version there is an estimate "5"). The right answers to the next 5 issues of the tour bring the title of "Master" with the presentation of a diploma or "medal" (in the estimated version - two marks "5").
Each player has the opportunity to use three tips:- 50 to 50: Of the four options for answers, 2 incorrect are cleaned;
- team assistance: the player comes to his team and within 30 s discussing a given question with her;
- Help hall: class disciples raise a sign with that letter under which, in their opinion, is the right answer. (Assistants consider the quantitative ratio of letters and declare the result. The teacher can encourage the most productive student, for which assistants record the options for the answers of the hall in the list of teachers.)The duration of the game can be from 40 to 80 minutes (from 3 to 6 qualifying and main tours, respectively). At the end of the game, the results are summed up, winners are awarded.
"Who will be a magnet of genetics?"
I Selection Tour
Position the diploid chromosomal sets of animals in the order of their numerical increase:
a) drosophila;
b) a bog turtle;
c) chimpanzees;
d) Askarida.
Answer:
d) 2 chromosomes;
a) 8 chromosomes;
c) 48 chromosomes;
b) 50 chromosomes.Note. In this and the subsequent qualifying tours, participants just specify only the sequence of letters, and the data (in this case, the number of chromosomes) is not necessary.
I main tour
1. Autosomes are:
a) additional chromosomes in the cell;
b) cells capable of reproducing themselves;
c) organelles capable of reproducing themselves;
d) incomplete chromosomes.2. The term "gene" to refer to the hereditary deposit of the body was proposed:
a) Johann Gregor Mendel;
b) Wilhelm Ludwig Iohansen;
c) Thomas Khantom Morgan;
d) Hugo Marie de Frisole.3. In the cells of the pine leaves there are 24 chromosomes; In the endosperm of pine seeds them:
a) 12;
b) 24;
c) 36;
d) 48.4. All mammals, including a person, is homogamed by the floor:
a) female;
b) male;
c) male and female;
d) in some cases - male, in others - female.5. The offspring may appear new signs that are not characteristic of parents, because:
a) with fertilization, the gameta merges randomly;
b) Mutations often occur in parents' govetakes;
c) the descendants have parent genes combined in new combinations;
d) one half of the genes offspring receives from the mother, the other - from the Father.6. Outbriding is:
a) change in hereditary deposits in closely related crossing;
b) the method of crossing, which does not lead to the emergence of new signs and properties;
c) crossing individuals of one species not consistent in direct relationship;
d) crossing individuals of different types.7. Dogs hanging her ear dominates over standing. When crossing two dogs with hanging ears, 14 individuals were obtained with hanging ears and 4 with standing. What are the genotypes of crossings:
but) AA H. AA;
b) AA H. AA;
in) AA H. aA;
d) AA H. AA.8. Dutch scholar Gogo de Freez tied together the theory of two scientists:
a) Darwin and Lamarka;
b) Darwin and Mendel;
c) Geckel and Lamarck;
d) Geckel and Mendel.9. What offspring can be obtained from normal on the basis of the blood coagulation of a homozygous woman and a man-hemophilic:
a) boy - hemophilic, girl - carrier of a defective gene;
b) healthy boy, girl - carrier of a defective gene;
c) healthy boy, girl - hemophilic;
d) healthy boy, healthy girl.10. After the occurrence of chromosomal mutation, the individual lost the ability to cross with individuals of its type. Should this individual be considered a new type:
a) yes, because The main criterion of the species is reproductive isolation;
b) yes, because Chromosomal mutation can lead to a root change in the characteristics of this body;
c) no, because species consist of populations, and evolution goes when changing generations; the new kind It is formed when a population is formed from such individuals;
d) no, because Chromosomal mutation does not affect genes and therefore does not play roles in evolution.Answers:
1 - g;
2 - b;
3 - a;
4 - a;
5 - in;
6 - in;
7 - g;
8 - b);
9 - b;
10 - in.II qualifying tour
Place the main discoveries in the field of genetics in chronological order:
a) the law of the relative frequency of the occurrence of dominant and recessive alleles Hardy-Weinberg;
b) Mutational theory of Gogo de Frise;
c) the laws of inheritance of mono- and polygenic signs of G. Amandel;
d) chromosomal theory of inheritance of T. Mamargan.Answer:
c) 1855-1856;
b) 1901-1903;
a) 1908;
d) 1910II main tour
1. The gene is located as part of the structure:
a) RNA;
b) DNA;
c) ATP;
d) protein.2. The main method of studying the patterns of heredity and variability applied by G. Penelle:
a) cytogenetic;
b) genealogic;
c) statistical;
d) hybridological.3. The locked inheritance of genes localized in one pair of homologous chromosomes installed:
a) G.Meldel;
b) T. Mozrigan;
c) V. Ioogansen;
d) D. De Friz.4. Drops have a chromosomal set:
a) haploid;
b) diploid;
c) triploid;
D) Tetraplaidoid.5. Selection B. clean lines It makes no sense because all individuals are:
a) the same phenotype;
b) the same genotype;
c) different phenotype;
d) different genotype.6. It is known that the Cyndactilian gene (fits of index and middle fingers) is localized in the Y-chromosome. How will this anomaly will be inherited in children born from marriage healthy on this sign of a woman and men with controversy:
a) all children will be with anomaly;
b) all children will be healthy, because The mother is healthy for this sign;
c) girls are healthy, but every second boy with anomaly;
d) all boys will be with an anomaly.7. In the boy IV blood type, and his sister - I group. About blood groups of their parents can be said:
a) both parents have an IV blood group;
b) one of the parents has I, and the second - IV group of blood;
c) one of the parents has II, the other - III group of blood;
d) these children have different fathers.8. The boy has Down Syndrome. What was the hames combination at fertilization? Set of chromosomes in gates:
1) (23 + x);
2) (21 + y);
3) (22 + xx);
4) (22 + y).Choose the correct answer:
a) 1 and 2;
b) 1 and 3;
c) 1 and 4;
d) 3 and 4.9. The laminacy gene in some plants is the gene of incomplete dominance in relation to the nipple genuine. When crossing the broad-sized and narrow-walled plants, you can expect the result:
a) all broad-sized;
b) all narrowed;
c) the ratio of broad and narrow-mounted 1: 1;
d) all plants with medium width leaves.10. If the DNA was not included in the DNA, and 5 bases, and the genetic code would not be triplet, but a tetraplet (i.e. codon would consist of four bases), then the total possible number of codons would be:
a) 125;
b) 256;
c) 625;
d) 1024.Answers:
1 - b;
2 - g;
3 - b;
4 - a;
5 B;
6 - g;
7 - in;
8 - in;
9 - g;
10 - in.III Qualifying Tour
In what order were awarded Nobel Prize per outstanding achievements and the discovery of fundamental laws of genetics?
a) Robert Holly, Haru Gobundu Quran and Marshall Nirenberg for decoding genetic code and its functions in the synthesis of proteins;
b) Herman J. Muller for the opening of the occurrence of mutations under the influence of X-rays;
c) Thomas Hunt Morgan for the opening of the functions of chromosoma as heredity carriers;
d) Francis Scream, James Watson and Mauris Wilkins for establishing a molecular structure nucleic acid And her role in the transfer of information in live matter.Answer:
c) 1933;
b) 1946;
d) 1962;
a) 1968III main tour
1. The number of combinations of Games digerozygous parental individuals with digibrid crossing is:
a) 4;
b) 6;
at 8;
d) 16.2. The method not acceptable in human genetic studies:
a) cytogenetic;
b) biochemical;
c) hybridological;
d) genealogic.3. The law that allows you to determine the frequencies of the dominant and recessive genes in the population in the frequency of occurrence of the phenotype, is called the law:
a) G.Meldey;
b) T. Mamargan;
c) N.Vavivova;
d) Hardy Weinberg.4. If the woman's oral epithelium cell nuclei has been detected by one y-chromatin and X-chromatin is found, its chromosomal set:
a) 45, X0.;
b) 46, Xx;
c) 46, XY.;
d) 47, XXY..5. The combination of all hereditary cells of the cell or the body is:
a) genes;
b) genome;
c) genotype;
d) Genofund.6. The type of interaction of genes in which one gene does not allow manifest itself in the phenotype of another pair of genes, is called:
a) complementaryness;
b) Pleotropy;
c) epistasis;
d) polymeria.7. Down syndrome is caused by the appearance of unnecessary chromosome in the 21st pair. It should be considered:
a) chromosomal mutation;
b) gene mutation;
c) genomic mutation;
d) somatic mutation.8. The first pair of possible parents has blood groups II and III, the second - IV and III. The child has I group of blood. Who is the parents of the child:
a) may be I, and II steam;
b) neither I, nor II steam;
c) only I steam;
d) only II of steam.9. BUT - Karya eye color, but - Blue eye color, IN - dark hair, in - blonde hair. The likelihood of the birth of a blue-eyed blond child from digerozygous on these signs of parents is equal to:
a) 9/16;
b) 3/16;
c) 1/16;
d) 0.10. What is the ratio of the genotype frequency AA, AA and aA Responsible to the Hardy Weinberg law:
a) 0.25; 0.50; 0.25;
b) 0.36; 0.55; 0.09;
c) 0.64; 0.27; 0.09;
d) 0.29; 0.42; 0.29.Answers:
1. - d);
2. - B);
3. - d);
4. - B);
5. - c);
6. - d);
7. - B);
8. - B);
9. - B);
10. - a).1. List what features genotypes of descendants arising from sexual reproduction are characterized. Why do these new organisms intensify opportunities for adapting to the conditions ambient?
The genotype of descendants arises by a combination of genes belonging to both parents. The emergence of new gene combinations provides greater survival of individuals, more successful and rapid propagation of the species to changing conditions.2. Find the first step of the formation of genital cells in the paragraph. What process ensures the emergence of many cells from one primary? What is the "reproductive period in the life of animals and plants"?
The first stage is a period of reproduction. In it, primary sex cells are divided by mitosis. The reproductive period in the life of animals and plants is a period in which an animal or plant can participate in sexual reproduction.3. Describe the second stage of Gametogenesis - a period of ripening of genital cells of male and female organisms. What features is this period? Why is a modified or new set of genes formed in the govetas in the process of maturation?
Stage of growth - cells increase in size and turn into sperm and oocytes I of order. This stage corresponds to Interfase I MEIOS. The DNA molecules are replicated under the unchanged chromosomes.
The stage of maturation is the third stage of gametogenesis. At this time, genes are recombongated, the conjugation of chromosomes and cross hinge during meyosis. Therefore, a new, modified gene set is formed.4. Name the levels of formation of new combinations of genes.
1. Crossing heer
2. Independent discrepancy chromosome in MEYIZE
3. Merge Games for fertilization.5. Using the drawing in the textbook, describe the changes occurring with chromosomes during the crosslinker.
A pair of conjugated chromosomes forms a bivalent or a tetrade. In the future, a crosslinker occurs between the chromosomes of the bivalent - this is the phenomenon of the metabolism of homologous chromosomes. At each such point, which is called chiam, two of the four chromatids crosses. By the end of the opposite between conjugated chromosomes, repulsion force arise. Two homologues remain connected at those points where the crossfielder between the father's and maternal chromatids occurred.6. Explain why Meiosis is the basis of combinative variability.
Cells formed as a result of meiosis differ in the set of chromosomes. Due to the accident rate of chromosomes during anAphase, 1 cells receive a wide variety of combinations of parent chromosomes. Considering the exchange of homologous sections of chromosomes in Proofase 1, each generated cell is unique and unique on the set of genes.1. What is combinative variability? Give examples. Name the sources of combinative variability.
The combinative variability is the variability of the offspring, due to the emergence of new combinations (combinations) of parents genes.
Sources of combinative variability are: crosslinker, independent discrepancy chromosome in Anafase I MEIOS, a random combination of weights in fertilization. The first two processes provide the formation of weights with different combinations of genes. The random merger of Games leads to the formation of a zygote with various combinations of genes of both parents. As a result, hybrids appear new combinations of parental signs, as well as new signs that the parents were not. The structure of genes does not change.
An example of combinative variability can be the birth of children with I or IV blood group in heterozygous parents with II and III blood groups (the descendants have new signs other than parental). Another example may be the appearance of flies with a gray body, with a rugged wings and with a black body, normal wings when crossing the digerozygous drosophila (gray body, normal wings) with a black male having a staple wings. In this case, a new combination of signs of parents arose in the proceedings due to cross hinge.
2. Give the definition of the concepts of "mutation", "Mutagenez", "Mutagen". Which groups are customary to share mutagens? Give examples.
Mutation - inherited change in the organism genetic material.
Mutagenesis - the process of mutations.
Mutagen is a factor leading to mutations in living organisms.
3. Describe the main types of gene, chromosomal and genomic mutations.
● Gene mutations - changes in the nucleotide sequence of DNA within the same gene. This is the most common type of mutation and the most important source of hereditary variability of organisms. Genital mutations include inserts, loss and replacement of nucleotides.
● Chromosomal mutations are changes in the structure of chromosomes. Distinguish intrahromosomal and interchromosomal mutations. The intrachromosomal mutations include: loss of the chromosome (deletion) section, double or repeatedly repeat the chromosome fragment (duplication), rotation of the chromosome section 180 ° (inversion). Interchromosomal mutations include the exchange of sections between two non-homologous chromosomes (translocation).
● Genomic mutations are a change in the number of chromosomes in cells. Among genomic mutations, polyploydia and heteroploidia are isolated.
Polyploidy is an increase in the number of chromosomes in cells, a multiple of a haploid set. For example, 3N (Triploidy), 4N (tetraploidy), 6N (hexaploidy), 8N (octaploidy). Polyploidy is distributed mainly in plants. Polyploid forms have large leaves, flowers, fruits and seeds, are distinguished by increased resistance to adverse environmental factors.
Heteroploidy (Aneuplody) is a change in the number of chromosomes, not a multiple of the haploid set. For example, 2N - 2 (Nullisomia, if there is no pair of homologous chromosomes), 2n - 1 (monosomy), 2n + 1 (trisomy), 2N + 2 (Tetrasomia), 2N + 3 (pentasomy).
4. What types of mutations are distinguished by origin? By type of mutated cells? According to the impact on the viability and fertility of the organisms?
● By origin, spontaneous and induced mutations are distinguished. Spontaneous mutations arise spontaneously throughout the life of the body in normal environmental conditions for it. Induced call mutations, artificially caused by mutagenic factors under experimental conditions. Induced mutations arise many times more often than spontaneous.
● The type of mutated cells allocate somatic and generative mutations. Somatic mutations occur in somatic cells. They can manifest itself in the individual itself and transmitted to the offspring in vegetative reproduction. Generative mutations occur in genital cells and are transmitted to offspring during sexual reproduction.
● According to the impact on the viability and fertility, individuals distinguish with lethal, half-liters, neutral and useful mutations. Lethal mutations lead to the death of the body (for example, in humans, the lack of X-chromosomes in the set causes fetal death in the third month embryonic development). Collective mutations reduce the viability of mutants (hemophilia, congenital form of diabetes, etc.). Neutral mutations do not have a significant impact on the viability and fertility of individuals (the appearance of freckles). Useful mutations increase the adaptation of organisms to the conditions of the medium (mutations caused by immunity to certain pathogens of diseases - HIV, malaria plasmodium, etc.)
5. What is the fundamental difference between combinative and mutational variability? What is the difference between mutational variability from the modification?
The basis of the occurrence of mutational variability is a change in genetic material: the structure of genes, structure or chromosome is changing. The combinative variability is due to the appearance of new combinations of parental genes in the offspring, while the structure of genes, the structure and the number of chromosomes remain unchanged.
Mutations, unlike modifications:
● inherit;
● Do not develop gradually, and suddenly occur;
● do not form continuous ranges of variability and do not have the reaction norms;
● are non-directional (uncertain);
● Manifest individually, and not worried.
6. What is the essence and practical importance of the law homologous rows hereditary variability?
The essence of the law of homologous series of hereditary variability lies in the fact that species and labor, close genetically related to the unity of origin, are characterized by similar series of hereditary variability. Knowing what form of variability is found in one species, you can foresee the finding of similar forms in other species.
The law N. I. Vavilov is of great practical importance for breeding and agriculture, since it predicts certain forms of variability in plants and animals. Knowing the nature of variability in one or several close species, it is possible to purposefully look for forms that are not yet known for this species, but already open from the forms related to it. Thanks to the law of homologous series, medicine and veterinary medicine has be able to endure knowledge about the mechanisms of development, the flow and methods of treating diseases of some species (in particular, humans) to others, closely related.
7. In wheat-one-rail machinery, Gamet contains 7 chromosomes. How many chromosomes are contained in somatic cells of mutants of wheat-one-one-room, if nullisomy led to the emergence of a mutant form? Monosomy? Triploidy? Trisomy? Tetraplaidia? Tetrasomia?
At Nallisomy, somatic cells contain a set 2N - 2 (14 - 2 \u003d 12 chromosomes), with monosomy - 2n - 1 (14 - 1 \u003d 13 chromosomes), with tripleoids - 3N (21 chromosome), with trisomy - 2n + 1 (14 + 1 \u003d 15 chromosomes), with tetraploidy - 4n (28 chromosomes), with tetrasomy - 2N + 2 (14 + 2 \u003d 16 chromosomes).
eight*. Black wool painting in cats dominates red, heterozygous cats have a turtle color - black spots alternate with red. Gennes controlling the color of the wool are located in the X chromosome. Theoretically cats, i.e. males, with the turtle color should not be (why?), However, sometimes they are born. How to explain this phenomenon? What do you think, what other features (except for unusual color) are characteristic of the turtle cats?
The turtle color is due to the simultaneous presence in the genotype of two different alleles - dominant (for example, a - black wool) and recessive (A - red-haired wool). In the norm of a cat (i.e. females) have two X chromosomes, and cats are only one (a set of genital chromosomes - XY). Therefore, cats can be black (x and x a), red-haired (x and x a) or turtle (x and x a), and cats are only black (x a y) or red (x a y).
However, sometimes due to the non-separation of sex chromosomes in meyosis (in the formation of Games from one of the parents), male kittens with a set of genital chromosomes XXY are born. Such cats may have a turtle color (x a x a y). However, most cats having a set of genital chromosomes XXY due to the presence of excess X-chromosome is disturbed by the spermatogenesis process, and they are fruitless (sterile).
* Tasks marked with stars, suggest the nomination by students of various hypotheses. Therefore, when setting a mark, the teacher should be guided not only for the answer given here, but to take into account each hypothesis, assessing the biological thinking of students, the logic of their reasoning, the originality of ideas, etc. After that, it is advisable to acquaint students with the answer given.
The combinative variability is a process based on recombination formation. In other words, such combinations of genes are formed, which are absent from parents. Next, the combinative variability and its mechanisms will be considered.
Causes of the process
The combinative variability is due to sexual reproduction of organisms. As a result, a large variety of genotypes is formed. As practically unlimited sources of genetic variability are certain phenomena. Sources that will be listed below, acting independently, simultaneously provide continuous "shuffling" in genes. It provokes the appearance of organisms with other fena and genotype. At the same time, the genes themselves are not subject to change. At the same time notes that new combinations are fairly easily disintegrated during the transmission process from generation to generation.
Sources
Description
Combinative variability is considered the most important source of all existing enormous diversity, which is characteristic of organisms. The sources listed above are, however, do not generate any significant importance for the survival of stable changes in the genotype, which, according to the theory of evolution, is necessary for the emergence of new types. Changes in this kind may occur when mutations.
Value
Combinative variability can explain, for example, why the child had a new combination of signs of relatives for paternal and mother lines. Moreover, it is possible to carry out a study of certain and specific options that are not peculiar to parents nor previous generations. Combinative variability contributes to the creation of genotypes in the offspring. It is of particular importance for the entire evolutionary process. First of all, the species variety of material for natural selection without lowering the viability of individuals is increasing. In addition, there is an increase in the possibilities of adapting organisms to regularly changing environmental conditions. This ensures the survival of the form (population, group) as a whole.
Using
Combinative variability applies to selection to obtain more valuable in economic meaning Inheritance complexes. Thus, phenomena of increasing viability, heterosis, growth intensity and other properties in the process of hybridization between representatives of different varieties or subspecies, which, in turn, causes a certain and significant economic effect. The opposite result is noted with a closely related crossing (inbreeding) - the combination of organisms with common ancestors. This kind of origin increases the likelihood of the presence of identical alleles of genes. Consequently, the risk of homozygous organisms increases. The highest degree of close-based crossing is observed in self-pollution in plants, as well as self-exploitation in animals. In this case, homozygosity increases the likelihood of manifestation of allele genes of recessive type. Their mutagenic changes provoke organisms with different hereditary anomalies.
Medico-genetic counseling
The results obtained in the study of combinative variability are actively used in predicting the offspring and explaining the meaning of genetic risks. In the process of counseling future spouses, the establishment of a possible presence in each individual of the alleles, which have passed from one ancestor and having an identical origin. In this case, the coefficient of kinship is applied. It is expressed in the fractions of the unit. For homozygous twins, the coefficient is 1, for children and parents, sisters and brothers - 1/2, the nephew and uncle, grandson and grandfather - 1/4, at the secondary sisters and brothers - 1/32, at the cousins \u200b\u200b- 1/8.
Examples
Consider the "Night Beauty" flower. He has a red (a) and white color of the petals. The body AA petals have pink color. The flower does not have a source gene of pink. It appears in the process of combinations of white and red elements. One more example. A person has a sickle-cell anemia. Death is aa, a AA is the norm. Sickle-cell anemia is aa. With this pathology, a person is unable to transfer physical exertion. But at the same time he is not sick with malaria, that is, the pathogen of this disease - plasmodium - can not consume wrong hemoglobin. This feature is important in the equatorial belt. This combinative variability appears when a combination of genes A and A.
Strengthening heredity
Some emerging mutations begin to adjacent to others, to enter into genotypes. In other words, many allelic combinations appear. For any individual, genetic uniqueness is characteristic. The exception is only the same twins and individuals, which arose as a result of a crucible breeding in a clone, having one cell as a generator. If we assume that for each pair of homologous chromosomes there is only one pair of allele genes, then for a person whose haploid set is 23, the number of possible genotypes can be 3 in the 23rd degree. This colossal number exceeds 20 times the number of residents of the Earth. But in reality, the difference between homologous chromosomes takes place in several genes. In calculations, the phenomenon of cross hinge is not taken into account. In this regard, the number of probable genotypes is expressed by astronomical numbers, and with confidence it is possible to say that the appearance of two completely identical people is impossible practically. The exception is the same twins that appeared from one egg. All this makes it possible to determine a reliably personality on the remains of living fabric and refute / confirm the paternity / motherhood.
complementarity;
