Genetics - the science of the laws of heredity and variability. The main task of genetics is to study the following problems:

1. Storage of hereditary information.

2. The mechanism of transmission of genetic information from generation to generation of cells or organisms.

3. Implementation of genetic information.

Change in genetic information (study of types, causes and mechanisms of variability).

Development of methods for using genetic engineering to obtain highly effective producers of various biologically active compounds, and in the future, the introduction of these methods into the genetics of plants, animals, and even humans. The methods used in genetics are varied, but the main one is hybridological analysis, that is, crossing with subsequent genetic analysis of the offspring. It is used at the molecular, cellular (hybridization of somatic cells) and organismal levels. In addition, depending on the level of research (molecular, cellular, organismic, population), the object under study (bacteria, plants, animals, humans) and other factors, a wide variety of methods of modern biology, chemistry, physics, and mathematics are used. However, whatever the methods, they are always auxiliary to the main method - genetic analysis. In 1865, the monk Gregor Mendel (who studied plant hybridization in the Augustinian monastery in Brunn (Brno), now in the Czech Republic) published at a meeting of the local society of natural scientists the results of research on the transmission of traits by inheritance when crossing peas (work Experiments on plant hybrids was published in the Proceedings of the Society in 1866). Mendel showed that some hereditary inclinations do not mix, but are transmitted from parents to offspring in the form of discrete (isolated) units. The patterns of inheritance formulated by him were later called Mendel's laws. During his lifetime, his work was little known and was perceived critically (the results of experiments on another plant, beauty of the night, at first glance, did not confirm the revealed regularities, which critics of his observations very willingly used).

Hybridological analysis is a fundamental method of genetics, its main provisions.

hybridological method- the study of inheritance by hybridization (crossing), that is, the combination of two genetically different organisms (gametes). The heterozygous organism that is obtained in this case is called a hybrid, and the offspring is called a hybrid.

Basic principles of the hybridological method:

1) purebred (homozygous) parental organisms are used for crossing, which differ from each other in one or more pairs of alternative traits;

2) accurate quantitative accounting of offspring is carried out separately for each studied trait in a number of generations.

The hybridological method is not suitable for humans for moral and ethical reasons, and also because of the small number of children and late puberty, it is not possible to cross homosapiens in the experiment. Therefore, indirect methods are used to study human genetics.

The results were summarized by Mendel in the following three propositions:

• rule of uniformity of the first hybrid generation;
• splitting law of the second hybrid generation;
• hypothesis of gamete purity.

First generation uniformity rule:

when crossing homozygous individuals that differ from each other in one pair of alternative traits, all offspring in the first generation are uniform both in phenotype and genotype.

splitting rule. Second law.

When homogeneous hybrids of the first generation are crossed with each other (self-pollination or inbreeding), individuals with both dominant and recessive traits appear in the second generation, that is, splitting is observed.

According to Mendel's second rule, we can conclude that:

1) allelic genes, being in a heterozygous state, do not change each other;

2) during the maturation of gametes in hybrids, an approximately equal number of gametes with dominant and recessive alleles is formed;

3) during fertilization, male and female gametes carrying dominant and recessive alleles are freely combined.

T Thus, Mendel's second rule is formulated as follows: when crossing two heterozygous individuals, i.e., hybrids analyzed for one alternative pair of traits, in the offspring, splitting is observed according to the phenotype in a ratio of 3:1 and according to the genotype 1:2:1.

Hypothesis of "purity of gametes".

The splitting rule shows that although only dominant traits appear in heterozygotes, the recessive gene is not lost, moreover, it has not changed. Consequently, allelic genes, being in a heterozygous state, do not merge, do not dilute, do not change each other. During the formation of germ cells, only one gene from an allelic pair enters each gamete.

Mendel was a monk and took great pleasure in teaching mathematics and physics at a nearby school. But he failed to pass the state certification for the post of teacher. I saw his craving for knowledge and very high intelligence abilities. He sent him to the University of Vienna for higher education. There Gregor Mendel studied for two years. He attended classes in natural sciences, mathematics. This helped him to further formulate the laws of inheritance.

Difficult academic years

Gregor Mendel was the second child in a family of peasants with German and Slavic roots. In 1840, the boy completed six classes at the gymnasium, and the very next year he entered the philosophical class. But in those years, the financial condition of the family deteriorated, and the 16-year-old Mendel had to take care of his own food on his own. It was very difficult. Therefore, after completing his studies in philosophy classes, he became a novice in a monastery.

By the way, the name given to him at birth is Johann. Already in the monastery they began to call him Gregor. He did not come here in vain, as he received patronage, as well as financial support, which makes it possible to continue his studies. In 1847 he was ordained a priest. During this period he studied at the theological school. There was a rich library, which had a positive impact on learning.

monk and teacher

Gregor, who did not yet know that he was the future founder of genetics, taught classes at school and, after failing the certification, went to university. After graduation, Mendel returned to the city of Brunn and continued to teach natural history and physics. He again tried to pass the certification for the post of teacher, but the second attempt was also a failure.

Experiments with peas

Why is Mendel considered the founder of genetics? From 1856, in the monastery garden, he began to conduct extensive and carefully thought-out experiments related to the crossing of plants. On the example of peas, he revealed patterns of inheritance of various traits in the offspring of hybrid plants. Seven years later, the experiments were completed. And a couple of years later, in 1865, at meetings of the Brunn Society of Naturalists, he made a report on the work done. A year later, his article about experiments on plant hybrids was published. It was thanks to her that they were laid as an independent scientific discipline. Thanks to this, Mendel is the founder of genetics.

If earlier scientists could not put everything together and form principles, then Gregor succeeded. He created scientific rules for the study and description of hybrids, as well as their descendants. A symbolic system was developed and applied to designate signs. Mendel formulated two principles by which inheritance predictions can be made.

Late recognition

Despite the publication of his article, the work had only one positive review. The German scientist Negeli, who also studied hybridization, favorably reacted to the works of Mendel. But he also had doubts about the fact that the laws that were revealed only on peas could be universal. He advised that Mendel, the founder of genetics, repeat the experiments on other plant species. Gregor respectfully agreed with this.

He tried to repeat the experiments on the hawk, but the results were unsuccessful. And only after many years it became clear why this happened. The fact was that in this plant, seeds are formed without sexual reproduction. There were also other exceptions to the principles that the founder of genetics deduced. After the publication of articles by famous botanists, which confirmed the research of Mendel, since 1900, there was recognition of his work. For this reason, it is 1900 that is considered the year of birth of this science.

Everything that Mendel discovered convinced him that the laws he described with the help of peas were universal. It was only necessary to convince other scientists of this. But the task was as difficult as the scientific discovery itself. And all because knowing the facts and understanding them are completely different things. The fate of the discovery of genetics, that is, the 35-year delay between the discovery itself and its public recognition, is not at all a paradox. In science, this is quite normal. A century after Mendel, when genetics was already flourishing, the same fate befell McClintock's discoveries, which were not recognized for 25 years.

Heritage

In 1868, the scientist, the founder of genetics Mendel, became the abbot of the monastery. He almost completely stopped doing science. Notes on linguistics, bee breeding, and meteorology were found in his archives. On the site of this monastery is currently the Gregor Mendel Museum. A special scientific journal is also named in his honor.

Biology. General biology. Grade 10. Basic level Sivoglazov Vladislav Ivanovich

24. Genetics - the science of the laws of heredity and variability. G. Mendel - the founder of genetics

Remember!

What does genetics study?

Why is G. Mendel considered the founder of genetics?

What objects did G. Mendel work with?

What is the main method of studying heredity he developed?

The subject and basic concepts of genetics. Throughout the history of its existence, mankind has always been interested in the question of the reasons for the similarity of children and parents. Why does like breed like? "How he looks like his father!" – relatives exclaim, having come to the birthday party and looking at the young man who has grown up. “He has an absolute ear for music!” - Proudly announces his mother, who has the same quality. Pride for the younger generation shines in the blue eyes of the parents, and the hero of the occasion, blinking innocently with the same blue eyes, quietly eats the sweets prepared for the guests.

We inherit from our parents not only eye and hair color, nose shape and blood type. We inherit temperamental traits and movement patterns, a propensity to learn languages, and an aptitude for mathematics. We are born into the world with our own unique hereditary material, the program on the basis of which, under the influence of environmental factors, we will become what we are - unique and at the same time similar to previous generations.

Heredity and variability are two properties of living organisms, inextricably linked with each other like two sides of the same coin. The patterns of heredity and variability are studied by one of the most important areas of biology - genetics.

Heredity- this is the ability of living organisms to transfer their signs, properties and features of development to the next generation. Heredity provides material and functional continuity between generations, maintaining a certain order in nature. Some species may remain relatively unchanged for hundreds of millions of years. For example, many modern sharks are not much different from sharks that lived in the early Cretaceous more than 130 million years ago.

The cells of organisms do not contain ready-made traits of an adult, the inheritance of traits occurs at the molecular level. The main structures that provide the material basis of heredity are chromosomes. Strictly speaking, we do not inherit properties, but genetic information. The elementary structural unit of heredity is gene A section of DNA containing information about the structure of a single protein, tRNA or rRNA. Genotype- this is the sum of all the genes of the organism, that is, the totality of all hereditary inclinations.

Variability is the opposite of heredity. It lies in the ability of living organisms to acquire in the process of individual development differences from other individuals of their own and other species.

The set of properties and characteristics of an organism, which are the result of the interaction of the genotype of an individual and the environment, is called phenotype. We are born with a certain skin color, but as soon as we travel to more southern regions in the summer, our skin takes on a swarthy hue. With age, the iris of the eyes brightens and the hair turns gray. Diseases transferred in childhood can disrupt the growth or development of some organs. The implementation of hereditary information is under constant pressure from environmental factors. However, it should be noted that there are signs, the manifestation of which does not depend on the influence of the external environment. Wherever we live: in the north or in the south, no matter how we are fed in childhood and no matter what diseases we have, the blood type with which we were born will remain unchanged throughout our lives.

At the origins of genetics. The main patterns of inheritance of traits were first described in the second half of the 19th century. Austrian scientist Gregor Mendel (1822-1884). Mendel was not the first scientist who tried to answer the question: how are properties and signs transmitted from generation to generation? Many researchers before him crossed various organisms, trying to see some kind of system in the results. In an effort to achieve success as quickly as possible, researchers crossed different species, while obtaining sterile offspring, took complex, difficult-to-determine traits for study, and did not conduct accurate mathematical calculations.

Explaining why it was Mendel who was able to discover patterns in the transmission of traits from generation to generation, the English geneticist Charlotte Auerbach said: “The success of Mendel’s work in comparison with the studies of his predecessors is due to the fact that he possessed two essential qualities necessary for a scientist: the ability to ask nature the right question and the ability to correctly interpret the answer of nature.

Consider the main features of Mendel's work that allowed him to succeed:

– as experimental plants, Mendel used different varieties of sowing peas, so the offspring obtained in such intraspecific crosses was prolific;

- peas are a self-pollinating plant, i.e. the flower is protected from accidental ingress of foreign pollen; when setting up the desired crossing, Mendel removed the stamens to exclude the possibility of self-pollination, and then transferred the pollen of another parent plant to the pistil with a brush;

- peas are unpretentious and have high fecundity;

– as experimental features, Mendel chose simple qualitative alternative features of the “either-or” type (purple or white flowers, yellow or green seeds); now it is difficult to say what played the main role here - luck or brilliant foresight, but it turned out that each pair of traits chosen by Mendel was controlled by one gene, which greatly simplified the interpretation of the results of crossing;

- when processing the data obtained, Mendel kept a strict mathematical record of the phenotypes of all plants and seeds.

For eight years, Mendel experimented with 22 pea varieties that differed from each other in seven ways. During this time, he studied a total of more than 10 thousand plants. By crossing different organisms and examining the resulting offspring, Mendel, in fact, developed a basic and specific method of genetics. hybridological method- this is a system of crossings in a number of generations, which makes it possible during sexual reproduction to analyze the inheritance of individual properties and characteristics of organisms, as well as to detect the occurrence of hereditary changes.

G. Mendel presented the results of his experiments in 1865 at a meeting of the Society of Naturalists in Brunn (the modern city of Brno) and outlined in the article "Experiments on Plant Hybrids". But Mendel's contemporaries did not appreciate the work, and for the remaining 35 years of the 19th century. his article was cited only five times.

Mendel's work was far ahead of the level of development of science at that time. Only when, in 1900, the laws of inheritance were rediscovered in three laboratories at once, did the scientific world remember that they had already been formulated 35 years ago. The year 1900 is considered the year of the birth of genetics, but the patterns established at one time by Gregor Mendel rightly bear his name.

Review questions and assignments

1. Give definitions of the concepts "heredity" and "variability".

2. Who first discovered the patterns of inheritance of traits?

3. On what plants did G. Mendel conduct experiments? Prove that the plants chosen by the scientist were the optimal object in these experiments.

4. Thanks to what features of the organization of work did G. Mendel manage to discover the laws of inheritance of traits?

Think! Execute!

1. Before G. Mendel, many researchers attempted to establish patterns of inheritance of traits from parents to children. However, they all ended in failure. How can you explain it?

2. Describe the phenotypes of contemporaries known to all (actors of theater and cinema, variety artists, politicians, etc.). Invite classmates to identify the person from the description.

3. The name of the science of phenology has the same root as the term "phenotype". What does phenology study? Why are these terms similar?

Work with computer

Refer to the electronic application. Study the material and complete the assignments.

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Genetics - the science of the laws of heredity and variability. The main task of genetics is to study the following problems:

1. Storage of hereditary information.

2. The mechanism of transmission of genetic information from generation to generation of cells or organisms.

3. Implementation of genetic information.

Change in genetic information (study of types, causes and mechanisms of variability).

Development of methods for using genetic engineering to obtain highly effective producers of various biologically active compounds, and in the future, the introduction of these methods into the genetics of plants, animals, and even humans. The methods used in genetics are varied, but the main one is hybridological analysis, that is, crossing with subsequent genetic analysis of the offspring. It is used at the molecular, cellular (hybridization of somatic cells) and organismal levels. In addition, depending on the level of research (molecular, cellular, organismic, population), the object under study (bacteria, plants, animals, humans) and other factors, a wide variety of methods of modern biology, chemistry, physics, and mathematics are used. However, whatever the methods, they are always auxiliary to the main method - genetic analysis. In 1865, the monk Gregor Mendel (who studied plant hybridization in the Augustinian monastery in Brunn (Brno), now in the Czech Republic) published at a meeting of the local society of natural scientists the results of research on the transmission of traits by inheritance when crossing peas (work Experiments on plant hybrids was published in the Proceedings of the Society in 1866). Mendel showed that some hereditary inclinations do not mix, but are transmitted from parents to offspring in the form of discrete (isolated) units. The patterns of inheritance formulated by him were later called Mendel's laws. During his lifetime, his work was little known and was perceived critically (the results of experiments on another plant, beauty of the night, at first glance, did not confirm the revealed regularities, which critics of his observations very willingly used).

Ticket number 7

1. The main components of the cell, their functions.

Cell - an elementary unit of the structure and vital activity of all organisms (except for viruses, which are often referred to as non-cellular life forms), having its own metabolism, capable of independent existence, self-reproduction and development.

All cellular life forms on Earth can be divided into two kingdoms based on the structure of their constituent cells:

prokaryotes(pre-nuclear) - simpler in structure and arose earlier in the process of evolution;

eukaryotes(nuclear) - more complex, arose later. The cells that make up the human body are eukaryotic.

The main elements of eukaryotic cells are:plasma membrane , surrounding each cell, determines its size and ensures that significant differences between the cellular content and the environment are preserved.

Membrane serves as a highly selective filter that maintains the difference in ion concentrations on both sides of the membrane and allows nutrients to penetrate into the cell, and excretory products to go outside. Cytoplasm - the contents of the cell, not including the nucleus, including the cytosol and organelles and limited by the cell membrane. Cytosol - This is the part of the cytoplasm that occupies the space between the membrane organelles. It usually accounts for about half of the total cell volume. The cytosol contains many intermediate exchange enzymes and ribosomes. About half of all proteins formed on ribosomes remain in the cytosol as its permanent components. Nucleus contains the main part of the genome and is the main site of DNA and RNA synthesis.

Cytoplasm surrounding the nucleus consists of the cytosol and the cytoplasmic organelles located in it. golgi apparatus consists of regular stacks of flattened membrane sacs called Golgi cisterns ; it receives proteins and lipids from the ER and sends these molecules to various points inside the cell, simultaneously subjecting them to covalent modifications. Mitochondria produce most of the ATP used in biosynthetic reactions that require free energy. Lysosomes contain digestive enzymes that destroy spent organelles, as well as particles and molecules absorbed by the cell from the outside by endocytosis. Entrained molecules and particles must pass through a series of organelles called endosomes on their way to lysosomes.