Concatenated inheritance of presentation traits. Linked inheritance of traits - - Thomas Morgan's Law. Vii. Homework

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Homework survey. 1. What does the law of independent inheritance of traits say + a diagram explaining the law? 2. What gametes are formed by organisms with genotypes VVCs, VvSS, VVSS, VvSs? 3. What kind of cross is called dihybrid, polyhybrid? 4. In what cases is the law of independent inheritance of characters fair?

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Morgan's law - genes located on one chromosome, during meiosis, fall into one gamete, that is, are inherited linked. R A. a × a. ... and V. in v. ... all R. burrow. black credits din. P A and a B in in F1 A. aa ... and V. in v. ... all R. burrow. black credits ... ... ... ... ... ... Dihybrid crossing of Drosophila flies. A - gray body a - black body B - normal wings c - embryonic wings F1 hybrids are similar to their parents.

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Crossing over disrupts linked gene inheritance. Crossover (crossing of chromosomes) is the mutual exchange of regions of homologous chromosomes, leading to the redistribution of genes localized in them. crossing over The farther apart genes are located on a chromosome, the higher the chance of crossing over between them. ... ... ... ... ... ... ... ... ... A B a c A a B c

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R a. ... Ah. ... and V. in × in. ... all R. burrow. black credits din. R a. ... Ah. V. . in v. F1 a. ... and A. and V. in v. ... in black. burrow. ser. credits Individuals with recombined characters 8.5% each

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Anchoring. 1. By crossing a tomato with a purple stem (A) and red fruits (B) and a tomato with a green stem and red fruits, 722 plants with a purple stem and red fruits and 231 plants with a purple stem and yellow fruits were obtained. Determine the genotypes and species of gametes of the parents, and in the first generation hybrids - the ratio of genotypes. 2. In fruit flies, genes that determine body color and wing shape are linked. A female with normal wings and a gray body was crossed with a male with a black body and reduced wings. In the first generation, all offspring had a gray body and normal wings. Determine the genotypes of the parents and offspring.

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Homework... § 3.8 Questions Tasks: 1. In dogs, the black color of the coat dominates over brown. From crossing a black female with a brown male, 4 black and 3 brown puppies were obtained. Determine the genotypes of the parents and offspring. 3. In tomatoes, the genes that determine the height of the stem and the shape of the fruit are linked, with the tall stem dominating over dwarfism, and the spherical shape of the fruit over the pear-shaped. What offspring should be expected from crossing a plant heterozygous for both traits with a dwarf one that has pear-shaped fruits. 2. In humans, dark hair color (A) dominates over light color (a), brown eye color (B) over blue (b). Write down the genotypes of the parents, the possible phenotypes and genotypes of the children born from the marriage of a blonde-haired, blue-eyed man to a heterozygous brown-eyed blonde woman.

Class: 9

Tasks:

To form knowledge about linked inheritance, linkage groups, genetic mapping;
To acquaint students with the causes of linked gene inheritance and the mechanism of its violation;
Form a system of knowledge about genetic sex determination and sex-linked inheritance of traits;
Strengthen the skill of solving genetic problems.

Equipment: computer, soft disks: “1C: Tutor. Biology + Variants of the Unified State Examination. 2006 "," Cyril and Methodius virtual school, biology tutor ", multimedia presentation on the topic of the lesson ( Annex 1), written survey cards, linked inheritance schemes, scheme family tree Queen Victoria and the incidence of hemophilia in descendants.

During the classes

I. Organizational moment

II. Knowledge check

In the previous lessons, you and I studied the fundamental laws of genetics - these are the three laws of G. Mendel and got acquainted with the cytological foundations of their action. Let's take a look at everything we've learned on this topic.

Slide:Questions:

What are the three laws of G. Mendel?
I law - the law of uniformity,II law - the law of splitting,III law - the law of independent inheritance.
What rules did G. Mendel follow when conducting his experiments?

used for crossing plants of different self-pollinating varieties - clean lines
to get more material for analysis, I used several parental pairs of peas
deliberately simplified the task by observing the inheritance of only one trait; I did not take into account the rest

Formulate the law of gamete purity. Who owns the discovery of this law?
When gametes are formed, only one of the two allelic genes gets into each of them.
Can the signs always be clearly divided into dominant and recessive?
In some cases, the dominant gene does not completely suppress the recessive gene from the allelic pair. In this case, intermediate signs appear.
What is the name of this phenomenon?
This phenomenon is called incomplete dominance.
Is it always possible to determine by phenotype which genes a given individual contains? Give an example.
Not always. A recessive trait always manifests itself only in a homozygous state, i.e. aa... A dominant trait can manifest itself in individuals with a homozygous or heterozygous genotype, i.e. AA or Aa.
Is it possible to establish the genotype of individuals that do not differ in phenotype? What method is used for this?
Yes, you can install. To do this, cross the studied individual with a recessive homozygote aa on the basis of the investigated character, called the analyzing crossing.
What are the features of dihybrid crossing?
Inheritance is considered and an accurate quantitative registration of offspring is made according to two pairs of alternative characters.
Is the law of independent inheritance always fair, i.e. H. Mendel's III law?
The law is valid only in cases where the genes of the considered traits are located in different non-homologous chromosomes.

III. Main part

Greetings from the class

So, the laws of G. Mendel have their limitations. After their discovery, science gradually began to accumulate facts that in some cases the splitting of signs does not occur according to the rules of G. Mendel. When analyzing this phenomenon, it turned out that the genes of the studied traits were on the same chromosome and were inherited together. Today we will talk about the features of such inheritance, find out if there are cases of its violation. We will also analyze the features of determining the sex of various living organisms and the mechanism of inheritance of sex-linked traits.

The topic of today's lesson is “Concatenated inheritance. Genetics of sex. "

Slide: “Linked inheritance. Genetics of sex. "

There are a lot of genes coding for various traits in any organism. For example, a person has about 100,000 genes, and there are only 23 types of chromosomes. Therefore, they all fit into these chromosomes. How are genes on the same chromosome inherited?

This question is answered by the modern chromosomal theory of heredity, created by T. Morgan.

Slide: Thomas Hunt Morgan

The main object with which T. Morgan and his students worked was the fruit fly Fruit fly... A dihybrid analyzing crossing was carried out on two grounds: the length of the wings and the color of the body. Experimental data showed that a splitting of features of 1: 1 is obtained instead of the expected 1: 1: 1: 1.

Slide: T. Morgan's experiment

Slide: T. Morgan's law

In the course of these studies, it was also proved that each gene has its own strictly defined place in the chromosome - a locus. Subsequently, this feature of the location of genes will be practically used to draw up genetic maps.

However, in Morgan's experiments, it turned out that among the first generation hybrids during crosses, a small percentage of flies appeared with a recombination of characters located on the same chromosome, i.e. violation of linked inheritance.

Slide: Breaking linked inheritance

It turned out that during the prophase of the first division of meiosis, homologous chromosomes can break at the site of contact and exchange allelic genes. This phenomenon is called - cross or crossing over.

Slide: Crossover

Most living organisms are represented by individuals of two types - male and female. How is it genetically determined whether an organism belongs to one or another sex?

Slide: Classification of the body's chromosomes

At the beginning of the twentieth century, T. Morgan found that males and females differ from each other by only one pair of chromosomes - sex chromosomes... The chromosomes in this pair are distinct from each other. The remaining pairs of chromosomes are the same and are called - autosomes... During the formation of gametes, a female will form one type of gametes: 3 autosomes + X chromosome, and males have two types of gametes: 3 autosomes + X chromosome or 3 autosomes + Y chromosome. If, during fertilization, a sperm with the X chromosome merges with an egg, then a female will develop, if with a Y chromosome, then a male.

Slide: What sex - homozygous or heterozygous does the sex of the future individual depend on?

- From heterozygous, i.e. containing sex chromosomes of different types

This fact is proved by the following scheme.

Slide: Splitting pattern by sex in Drosophila

In some species of living organisms, the chromosomal sex determination is completely different. Let's consider such cases.

Slide: Chromosomal sex determination

Slide: Do all genes found on sex chromosomes determine sex-related traits?

If the genes that determine any trait are located in autosomes, then the inheritance of the trait occurs regardless of who is its carrier - a man or a woman. If the genes of a trait are located on the sex chromosomes, then its inheritance will be determined by its location in the X or Y chromosome, and therefore by belonging to a particular sex.

Slide: Inheritance linked with floor

An example of such inheritance is the inheritance of such diseases in humans as hemophilia and color blindness. Genes that determine healthy and diseased traits are located on the X chromosome of the sex couple. In this case, the disease manifests itself in men, even though the diseased gene is in a recessive form.

Student messages about hemophilia and color blindness

Slide: Hemophilia

Information: Hemophilia- hereditary disease, transmitted by the recessive type linked to the X chromosome, manifested by increased bleeding.
It is inherited through the offspring of the patient's sisters and daughters. Carrier women transmit hemophilia not only to their children, but through carrier daughters - to grandchildren and great-grandchildren, and sometimes to later offspring. Boys are sick (hemophilia C is also found in girls).

There are three forms of hemophilia - A, B and C. In hemophilia A, factor VIII is absent, in hemophilia B - factor IX and in hemophilia C - factor XI of blood coagulation.

Slide: Color blindness m

Information: Color blindness, color blindness is a hereditary, rarely acquired feature of vision, expressed in the inability to distinguish one or more colors. Named after John Dalton, who first described a type of color blindness, based on his own feelings, in 1794. Dalton did not distinguish between red, but did not know about his color blindness until the age of 26. He had three brothers and a sister, and two of the brothers suffered from red color blindness. Dalton detailed his family vision defect in a small book. Thanks to her publication, the word "color blindness" appeared, which for many years became synonymous not only with the anomaly of vision in the red region of the spectrum described by him, but also with any violation of color vision.

V. Anchoring

And now, let's see how much you understood what was discussed in the lesson, and we will complete the prepared tasks.

Disk: test questions on the studied topic. (“Cyril and Methodius virtual school, tutor in biology”, “Cyril and Methodius virtual school, biology tutor”) questions # 238, 226, 217, 222, 254, 256.

Vi. Lesson summary

H. Mendel's laws have limitations
Genes located on the same chromosome are inherited together, i.e. linked
The phenomenon of a violation of linked inheritance is called crossing over.
Sex is determined by a pair of sex chromosomes
Genes found in the sex pair of chromosomes are inherited linked to the sex

Vii. Homework

Slide: Learn §3.8,3.10; Be able to answer questions after paragraphs.

Complete the written task on the cards.

Prepare reports on the types of gene interactions.

Solve the Problem An aspiring experimenter caught a mouse with surprisingly long, curled hair. He decided to develop a line of such mice in order to sell them as pets and get rich. To do this, he crossed her with a male with short, straight hair, which he bought at a pet store. Unfortunately, among the six offspring obtained, all had short, straight hair. Knowing that closely related crosses are permissible in mice, he crossed the original mouse (long wavy hair) with one of its offspring. Among the descendants, two mice had the desired characteristics, and the other six were similar to their father. Help the experimenter! Explain to him the results of his experiment and advise how to achieve the task.

Solve another problem In the fruit fly Drosophila melanogaster, gray body coloration dominates over black, and the gene for normal wing development dominates over underdeveloped wings. From crossing a fly with a gray body and normal wings with a fly with a dark body color and rudimentary wings, hybrids with a gray body and normal wings are obtained. The resulting hybrids are crossed with flies that have two recessive traits. Among the offspring, about 50% of the flies were with two dominant traits and about 50% with two recessive traits. Make a crossing scheme, explain the results obtained.

Thomas Morgan was the first to introduce the fruit fly to Drosophila as a genetic object of Drosophila melanogaster Thomas Hunt Morgan About T. Morgan's experimental works - the classic textbook "Genetics with the basics of breeding", by S.G. Inge-Vechtomov On T. Morgan's experimental works - a classic textbook "Genetics with the basics of selection", by S.G. Inge-Vechtomov

GEN A GEN B Allelic genes are located in identical regions of homologous chromosomes Linkage group - all genes located on one chromosome Homologous chromosomes GEN a GEN b Test for self-test - Lnekrasova.ru In the section "Biology lessons" Test for self-testing - Lnekrasova.ru In the section "Biology lessons"

The main thoughts of the lesson Gene - a section of a chromosome Genes are located in chromosomes linearly, each gene in its own locus In identical loci of homologous chromosomes there are allelic genes Genes localized on one chromosome are inherited together, forming a linkage group Morgan's law Chromosomal theory of heredity:

Resources: ozof.htm - Drosophila ozof.htm dical / Thomas_Morgan / - T. Morgan, portrait dical / Thomas_Morgan / = person & more = morgan - T. Morgan, portrait = person & more = morgan - T. Morgan, quote

summaries of other presentations

"Interaction of non-allelic genes" - The presence of pigment. Pink comb. Split. Modifying effect of genes. Recessive epistasis on the example of staining inheritance in mice. Types of interaction of non-allelic genes. Complementary interaction. Dominant epistasis on the example of color inheritance in horses. Additive polymer Interaction of non-allelic genes. Polymeric interaction of genes. Non-additive polymerization. Cleavage by phenotype.

"Mendel's third law" - Plant. Round shape of the fruit. The law of independent combination. Results. Color inheritance. Red coloration. Solving problems. Crossbreeding. Signs. The probabilities of the appearance of a particular genotype. Plants with rounded red fruits. Genotypes of parents. Organisms. Analyzed genes. Rh positive boy. Crossbreeding of heterozygous organisms. The probability of birth. Dihybrid crossing.

"Law of Independent Inheritance" - Correct definition all possible gametes. If there is work, then there will be success. Black color. Solution. Dihybrid crossing. Results of Mendel's experiments. Substantiations of the third law of G. Mendel. Plants have yellow smooth seeds. Good disposition. Punnett Lattice. Theoretical foundations of the third law of G. Mendel. Independent inheritance law.

"Regularities of monohybrid crossing" - Monohybrid crossing. The dominant variant of the trait. Inheritance of the color of pea flowers. Inheritance of the color of strawberries. Saturating crosses. Reciprocating crosses. Incomplete dominance. Cytological (cytogenetic) bases of the inheritance of traits. Analyzing crosses. First generation hybrids. Inheritance of the color of pea seeds.

"Genetics of Mendel" - Problem using the 3rd Mendel's law. Inferences. Gregor Mendel. Fundamentals of Genetics. Illustrations of the first and second laws of Mendel. Phenotype. Mendel's third law. An atmosphere of cooperation. Dihybrid crossing. Long-haired.

"Pedigree" - Blood types. Hair shape inheritance. Family pedigree. Hair color. Goals and objectives of the study. Hair shape. Genealogical method of human genetics. An autosomal recessive type of inheritance can be traced in the pedigree. Inheritance of blood groups in humans. Failure to distinguish between individual colors. Analysis of the pedigree. Pedigree.

Genes linked inheritance (PRESENTATION biology class in 10 classes with the use of ICTs) LESSON OBJECTIVES: discover the essence of phenomena linked inheritance GENE FORM knowledge of the basic provisions of the law T.MORGANA get acquainted with the principles of genetic maps to uncover the meaning of the genetic map for medicine and agriculture in developing logical thinking STUDENTS

LESSON PLAN 1. Actualization of knowledge 2. Learning new material 2.1 The general nature of the laws of G. Mendel. Exceptions. 2.2 Hypothesis of the chromosomal nature of heredity Discovery of material carriers of heredity Experimental substantiation of the chromosomal theory of heredity 2.3 Location of genes in the chromosome Crossover and its genetic consequences Genetic maps of chromosomes 2.4 Summary: the main provisions of T. Morgan's law 3. Fixing the material (testing) 4. Optional hour 4.1 Problem solving on the results of quantitative and qualitative accounting of splitting by genotype and phenotype in linked inheritance 4.2 Solving problems for compiling a chromosome map

THINK! 1. For which genes is G. Mendel's law of independent inheritance applicable? Answer: For genes belonging to different alleles located in different pairs of homologous chromosomes. 2. What is the name of the chromosome region where the gene is located? Answer: Locus 3. What phenomenon is shown in the diagram? Answer: Crossover, or gene recombination. 4. What is the essence of this phenomenon? Answer: Crossover is the exchange of DNA regions in a pair of chromatids from homologous chromosomes in prophase I of meiosis.

The general nature of the laws of G. Mendel Year - the year of birth of the science of genetics G. de Vries - Dutch botanist (working with poppy seeds) K. Correns - German botanist (working with corn) E. Cermak - Austrian botanist (working with peas) Batson - English biologist (experiments with chickens) Geno - French zoologist (experiments with mice) Exception: do not give independent splitting into F 2 the following signs Pollen shape and color of flowers in sweet pea Red color of flowers and dark stems and leaves in plants Long neck and long limbs in animals (and vice versa) Dark eyes and dark hair in humans (and vice versa)

Hypotheses of the chromosomal theory of heredity 1903 - the assumption of finding many genes in the chromosome and their joint inheritance W. Setton, American biologist O. Hertwig, German biologist 1909 - the experiments of American biologists with the fruit fly Drosophila T. Morgan and his collaborators: K. Bridges G.J. Meller A. Stertevant

The object of research is Drosophila Reasons for choosing: Rapid reproduction (3 generations per month) Small number of chromosomes (4 pairs) Well-noticeable external differences Drosophila mutants in wing structure: A - with serrated wings, B - with underdeveloped wings, C - with curved wings, G - wingless

Linkage groups Linkage genes are genes located on the same chromosome and inherited together. The number of genes in different linkage groups (that is, different chromosomes) can differ from each other. The number of linkage groups is equal to the number of chromosomes in the haploid set: Drosophila - 4 Peas - 7 Corn - 10 Mouse - 20 Human - 23 Earthworm - 36 Lizard - 38 Rabbit - 44 Cow -60

Crossover frequency and distance between genes The frequency of recombinations is determined by the formula, where N is the number of recombinants, N 0 is the total number of offspring. Morganida is a unit of distance between linked genes equal to 1% crossing over. The frequency of gene recombinations shows the relative location of linked genes on the chromosome: the farther from each other the genes are, the higher the frequency of recombination. This circumstance is used in drawing up genetic maps.

Genetic maps A genetic map is a diagram of the relative location of genes on the same chromosome. Shows: 1. The sequence of the location of genes in the chromosome 2. Distance between genes Genome - the totality of all genes of the haploid set of chromosomes.

The principle of constructing a genetic map Triangulation method - determining the relative position (sequence) of the loci of three or more genes. Generating a genetic map for genes A, B, C, the recombination frequencies between which are A - B = 6%, B - C = 14%, A - C = 8%.

The main provisions of the law of linked inheritance by T. Morgan Genes located in one chromosome form a linkage group and are inherited together. The clutch is complete and incomplete. In case of incomplete linkage, homologous chromosomes exchange their regions, which makes it possible for new combinations of genes to arise. For genes whose loci are separated by large distances, double crossing over is characteristic, when recombination occurs simultaneously at two points.

TESTING Determine in the figure between which genes the probability of overlap is highest: 1 option 2 option 3 option 4 option a) HELL b) BC c) AB d) VD a) Ab and ab b) sun c) cd and cd d) Ade and aD a) AB and av b) AS and ac c) Vd and vd d) Hell and hell a) Ad b) ab c) sun and vC d) ac and aC

Solving genetic problems On the results of quantitative and qualitative registration of splitting by genotype and phenotype. Task: Two breeds of rabbits were crossed: spotted normal-haired and completely colored Angora. In F1, all rabbits are spotted and normal-coated. As a result of the analyzing crosses, 26 spotted angora, 144 completely colored angora, 157 spotted with normal wool and 23 completely colored with normal wool were obtained. Questions: 1. How many different phenotypes will result from such a crossing? 2. What percentage of female gametes contains both spotted and angora wool genes? 3. What percentage of gametes contains genes of solid color and normal length? 4. What percentage of offspring from this cross will be phenotypically similar to the father? 5. What percentage of the offspring from this cross will be diheterozygous?

Given: A - gene for spotted coloration a - gene for solid coloration B - gene of normal length b - gene for angora wool - genotype of a female (for non-crossover offspring, of which more than 50%) - genotype of a male (since the crossing is analyzing) Р × Г F Answer: 1.4 phenotype 2.7.4% (26 ÷ 350100) 3.6.6% (23 ÷ 350100) 4.41.2% (144 ÷ 350100) 5.44.2% (157 ÷ 350100)

Solving genetic problems To compile a chromosome map Task: As a result of the analyzing crossing, the following splitting was obtained in tomatoes: A-B-C- 73 A-bbC- 2 A-B-cc 348 A-bbcc 96 aaB-C- 110 aavbC- 306 aaB -ss 2 aavvss Write the scheme of the analyzing crossing. 2. Build a map for the specified genes, indicating the distance between them.

Given: A-B-C- 73 A-bc-2 A-B-cc 348 A-bbcc 96 aaB-C- 110 aavvS- 306 aaB-cc 2 aavvss 63 - genotype of a female plant (according to non-crossover offspring, of which there are more than 50 %) - the genotype of the male plant (because the crossing is analyzing) Р × Г F non-crossover crossover

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