Linked inheritance of traits presentation. Linked inheritance of traits

Morgan's Law
G. Mendel traced inheritance
seven pairs of traits in peas. Many
researchers, repeating Mendel's experiments,
confirmed the laws discovered by them. Was
it is recognized that these laws are universal
character.
However, in 1906, English geneticists
V.Batson and R.Pennet, crossing
sweet pea plants and analyzing
inheritance of pollen shape and color
flowers, found that these signs were not
give independent distribution in
offspring. Descendants always repeated
signs of parental forms.
It became clear that not all genes are characterized by independent
distribution in offspring and free combination.
Each organism has a huge number of characteristics, and the number
There are few chromosomes. Therefore, each chromosome carries more than one
gene, but a whole group of genes responsible for the development of various traits.

Class: 9

Tasks:

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

Equipment: computer, software disks: “1C: Tutor. Biology + Unified State Exam Options.2006”, “Virtual school “Cyril and Methodius”, biology tutor”, multimedia presentation on the topic of the lesson ( Annex 1), written survey cards, linked inheritance diagrams, a diagram of the family tree of Queen Victoria and the incidence of hemophilia in descendants.

During the classes

I. Organizational moment

II. Check of knowledge

In previous lessons, we studied the fundamental laws of genetics - these are the three laws of G. Mendel and became acquainted with the cytological basis of their action. Let's remember everything we've learned on this topic.

Slide:Questions:

1. What are the three laws of G. Mendel?
   The first law is the law of uniformity,II law – the law of splitting,III law – the law of independent inheritance.
2. What rules did G. Mendel adhere to when conducting his experiments?
1. used to cross plants of different self-pollinating varieties - with clean lines
2. to get more material for analysis, I used several parent pairs of peas
3. deliberately simplified the problem by observing the inheritance of only one trait; didn't take the rest into account
3. Formulate the law of gamete purity. Who is responsible for the discovery of this law?
   When gametes are formed, only one of the two allelic genes enters each of them.
4. Can traits 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 arise.
5. What name did this phenomenon get?
   This phenomenon is called incomplete dominance.
6. Is it always possible to determine from the phenotype which genes a given individual contains? Give an example.
   Not always. A recessive trait always appears only in the homozygous state, i.e. ahh. And a dominant trait can manifest itself in individuals with a homozygous or heterozygous genotype, i.e. AA or Ah.
7. Is it possible to determine the genotype of individuals that do not differ in phenotype? What method is used for this?
   Yes, you can install it. To do this, cross the test individual with a recessive homozygote. ahh according to the trait under study, called analyzing crossing.
8. What are the characteristics of a dihybrid cross?
   Inheritance is considered and an accurate quantitative accounting of the offspring is made according to two pairs of alternative characteristics.
9. Is the law of independent inheritance always valid, i.e. III law of G. Mendel?
   The law is valid only in cases where the genes for the characteristics in question are located on different non-homologous chromosomes.

III. Main part

Greetings from the class

So, G. Mendel's laws have their limitations. After their discovery, facts gradually began to accumulate in science that in some cases the splitting of characters does not occur according to the rules of G. Mendel. When analyzing this phenomenon, it turned out that the genes for the traits under study were on the same chromosome and were inherited together. Today we will talk about the features of such inheritance and find out whether 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: “Chained inheritance. Genetics of sex."

Slide: "Chained inheritance. Genetics of sex."

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

This question is answered by the Modern Chromosome 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 Drosophila. A dihybrid analysis cross was carried out for two characteristics: wing length and body color. Experimental data showed that the resulting splitting of features was 1:1 instead of the expected - 1:1:1:1.

Slide: T. Morgan's experiment

Slide: T. Morgan's Law

During these studies, it was also proven 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 compile 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 recombination of characters located on the same chromosome, i.e. violation of linked inheritance.

Slide: Disorder of linked inheritance

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

Slide: Crossing over

Most living organisms are represented by individuals of two species - male and female. How is an organism's belonging to one sex or another determined genetically?

Slide: Classification of organism chromosomes

At the beginning of the twentieth century, T. Morgan established that males and females differ from each other in only one pair of chromosomes - sex chromosomes. The chromosomes in this pair are different from each other. The remaining pairs of chromosomes are identical and are called - autosomes. When gametes are formed, the female will produce one type of gamete: 3 autosomes + X chromosome, and males will produce two types of gametes: 3 autosomes + X chromosome or 3 autosomes + Y chromosome. If, during fertilization, a sperm with an X chromosome merges with an egg, then a female will develop; if with a Y chromosome, then a male will develop.

Slide: On what sex - homozygous or heterozygous does the sex of the future individual depend?

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

This fact is proven by the following diagram.

Slide: Pattern of sex segregation in Drosophila

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

Slide: Chromosomal sex determination

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

If the genes that determine a trait are located on autosomes, then the trait is inherited regardless of whether its carrier is a man or a woman. If the genes for a trait are located on the sex chromosomes, then its inheritance will be determined by its location on 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 human diseases such as hemophilia and color blindness. The genes that determine healthy and diseased traits are located on the X chromosome of a sexual 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- a hereditary disease transmitted by an X-linked recessive type, manifested by increased bleeding.
It is inherited through the offspring of the patient's sisters and daughters. Female carriers pass hemophilia not only to their children, but through carrier daughters to their grandchildren and great-grandchildren, and sometimes to later offspring. Boys are affected (hemophilia C also occurs 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: Colorblindness m

Information: Colorblindness, color blindness is a hereditary, less commonly 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 sensations in 1794. Dalton did not distinguish the color red, but did not know about his color blindness up to 26 years old. He had three brothers and a sister, and two of the brothers suffered from red color blindness. Dalton described his familial visual defect in detail in a short book. Thanks to its publication, the word “color blindness” appeared, which for many years became synonymous not only with the vision anomaly in the red region of the spectrum described by him, but also with any color vision disorder.

V. Consolidation

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

Disk: test questions on the topic studied. (“Virtual school “Cyril and Methodius”, biology tutor”, “Virtual school “Cyril and Methodius”, biology tutor”) questions No. 238, 226, 217, 222, 254, 256.

VI. Lesson summary

1. G. Mendel's laws have limitations
2. Genes located on the same chromosome are inherited together, i.e. linked
3. The phenomenon of violation of linked inheritance is called crossing over
4. Sex is determined by a pair of sex chromosomes
5. Genes located on the sex pair of chromosomes are inherited in a sex-linked manner

VII. Homework

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

Complete the written task on cards.

Prepare reports on types of gene interactions.

To use presentation previews, create a Google account and log in to it: https://accounts.google.com

Slide captions:

Linked inheritance of traits - - Thomas Morgan's Law Course "General Biology" Topic "Fundamentals of Genetics" 9th grade Moscow - 2009

Mendel's laws on the independent nature of the inheritance of traits are universal (experimentally confirmed) But!!! 1906, W. Betson, R. Punnett (England) – – exceptions to Mendel’s laws Beginning of the twentieth century – experiments of Thomas Morgan (USA) with the fruit fly Drosophila (convenient object) A little history...

The object of Morgan's genetic research was the fruit fly Drosophila. Advantages: Outwardly, the female and the male are distinguishable (his abdomen is smaller and darker). Unpretentious in conditions of detention. Short development cycle - after 14 days, numerous new offspring are hatched. A wide range of mutations expressed in morphological characters: body color, wing size, number of bristles, eye color. These mutations do not affect the viability of the fly

Analysis of exceptions to Mendel's laws. 2. Experimental and theoretical substantiation of linked inheritance of traits. 3. Creation of the chromosomal theory of inheritance. Works by Thomas Morgan

T. Morgan's chromosomal theory of inheritance Genes are located on chromosomes, their number is not the same. Each gene has a specific location on the chromosomes; Allelic genes are located in identical loci of homologous chromosomes. Genes are arranged linearly on chromosomes. Genes localized on the same chromosome form a linkage group and are inherited together. Number of linkage groups = n (haploid set of chromosomes). The linkage of genes can be disrupted as a result of crossing over. The frequency of crossing over is directly dependent on the distance between genes. Each species has a unique set of chromosomes - a karyotype.

P: Thomas Morgan's experiments (dihybrid crossing) Gray body Normal wings Black body Reduced wings AABB aabb F 1: 100% AaBb According to Mendel's I law, uniformity of characters is observed

Experiments by Thomas Morgan (return, analyzing crossbreeding) F 2: Parental combinations of traits New combinations of traits P: Gray body Normal wings Black body Reduced wings AaBb aavv Expected results of crossing if non-allelic genes are on different chromosomes: ? AaBv 2 5% aaBv 2 5% AaBv 2 5% aaBb 2 5%

Experiments by Thomas Morgan (return, analyzing crossing) F 1: Aabv - 8.5% aaBv - 8.5% New combinations of characters P: Gray body Normal wings Black body Reduced wings AaBb aavv Real crossing results: Parental combinations of characters AaBb - 41, 5% aavv - 41.5%

Cytological foundations of the law of linked inheritance of characters by Thomas Morgan A B a v a v a c Non-allelic characters lie in different loci of the same chromosome Inherited linked - - linkage group Conclusion: there should be no new combinations of characters in the offspring P: AaBb aavv

Cytological foundations of Thomas Morgan's law of linked inheritance of characters P: AaBb aavv A B a b a c G: F 1: AaBb aavv 5 0% 5 0%

Cytological foundations of Thomas Morgan's law of linked inheritance of traits How did new combinations of traits appear in the offspring? Reason: crossing over in prophase I of meiosis a in A B a A in B a B A in Such gametes are material for new combinations of characters

On the distance between genes. What determines the probability of crossing over? Unit of distance between genes – 1 morganid 1 morganid – 1% crossing over between genes

On the topic: methodological developments, presentations and notes

Worksheet. Individual development of organisms. Patterns of inheritance of traits established by G. Mendel. Monohybrid crossing.

Worksheet for independent work students. Textbook Kamensky A.A., Kriskunov E.A., Pasechnik V.V. Biology. Introduction to general biology and ecology. 9th grade...

Genetics of sex. Inheritance of sex-linked traits. Grade 10

This lesson is current in the section “Fundamentals of Genetics and Selection” in 10th grade (textbook by V.B. Zakharov, S.G. Mamontov, N.I. Sonin. Bustard. 2006). The material being studied is based on the students' knowledge...

Biology lesson in 9th grade "Patterns of inheritance of traits established by G. Mendel. (Types of crossing. solving genetic problems)

This presentation promotes students’ study of Mendel’s laws, there are formulations of the laws, and solutions to problems with complete and incomplete dominance and analyzing crossbreeding are shown. There are elements and...

Linked inheritance of traits Thomas Morgan Law

Genes located on the same chromosome during meiosis end up in one gamete, i.e. are inherited concatenated.

XX X Y

T. Morgan

• Front sight every two weeks at t= 25 C produces numerous offspring.
• The male and female are clearly distinguishable in appearance - the male has a smaller and darker abdomen.
• Flies can reproduce in test tubes on a cheap nutrient medium

Inheritance of wing length and color in fruit flies

The emergence of intermediate genotypes in which both alleles participated.

Conjugation and crossing over (prophase 1 meiotic division)

Biological significance:

• new gene combinations
• the emergence of hereditary variability
• selection of individual genes rather than combinations of them

Sex chromosomes and autosomes

Whose chromosome set?

How many autosomes?

Graphic representation of chromosomes

Detailed map Human X chromosomes

(370 diseases are linked to the X chromosome

in men, all diseases linked to the X chromosome are manifested in the phenotype)

COLOR BLINDNESS

Women get sick -0.5%

Men-8%

In table No. 1, people with normal vision see the number 16.

People with acquired visual impairment have difficulty or do not distinguish the number 96 in Table No. 2 at all.

The sex ratio in nature is 1:1 when crossing a heterozygote (Aa) with homozygote (aa)

Females - XX

Males – X0

grasshoppers, ants

sea ​​worm – bonelia (sex depends on external conditions)

Terms to remember:

• Linked genes –
• Genetic map of a chromosome -
• Chained inheritance –
• Crossing over –
• Conjugation –

• Morgan's Law -
• Autosomes and sex chromosomes -
• Homogametic and heterogametic sex

Problem 1 Which pairs are most advantageous to cross to produce platinum foxes, if platinum dominates over silver, but in the homozygous state the platinum gene causes the death of the embryo?

Problem 2

A pink comb is a dominant trait in chickens, while a simple comb is recessive. What will the offspring be like if you cross heterozygous hens with rose-shaped combs and homozygous roosters with simple combs?

Problem 3

When two white pumpkins were crossed in the first generation, ¾ of the plants were white and ¼ were yellow. What are the genotypes of the parents if white color is dominant over yellow?

ANSWER 1: it is most profitable to cross silver and platinum heterozygous foxes

ANSWER 2: 50% heterozygous chickens with

simple combs and 50% homozygous

roosters with pink combs

ANSWER 3: parent plants are heterozygous

Solve the problem A novice experimenter caught a mouse with surprisingly long, crimped hair. He decided to breed a line of such mice to sell them as pets and make a fortune. 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 produced, all had short, straight hair. Knowing that mice can inbreed, he crossed the original mouse (with long, wavy hair) with one of its offspring. Among the descendants, two mice had the desired characteristics, and the remaining six were similar to their father. Help the experimenter! Explain to him the results of his experiment and advise him on how to achieve his goal.

Solve another problem: In the fruit fly Drosophila melanogaster, gray body color dominates over black, and the gene responsible for the normal development of wings dominates the gene for underdeveloped wings. By crossing a fly with a gray body and normal wings with a fly that has a dark body color and rudimentary wings, hybrids are obtained that have a gray body and normal wings. The resulting hybrids are crossed with flies that have two recessive traits. Among the offspring, approximately 50% of the flies ended up with two dominant traits and approximately 50% with two recessive traits. Draw up a crossing diagram and explain the results obtained.

Thomas Morgan first introduced the fruit fly Drosophila as a genetic object Drosophila melanogaster Thomas Hunt Morgan About the experimental work of T. Morgan - the classic textbook “Genetics with the basics of selection”, author S.G. Inge-Vechtomov About the experimental work of T. Morgan - the classic textbook “Genetics with the basics of selection”, author S.G. Inge-Vechtomov

GENE A GENE B Allelic genes are located in identical sections of homologous chromosomes Linkage group - all genes located on the same chromosome Homologous chromosomes GENE a GENE b Test for self-test - Lnekrasova.ru In the section "Biology Lessons" Test for self-test - Lnekrasova.ru In the section "Biology Lessons"

The main ideas of the lesson Gene is a section of a chromosome Genes are located linearly on chromosomes, each gene in its own locus Identical loci of homologous chromosomes contain allelic genes Genes localized on the same chromosome are inherited together, forming a linkage group Morgan's law Chromosomal theory of heredity:

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