Tip 1: What is a gene and a gene

Miscellaneous

Tip 1: What is a gene and a gene

The development of the natural sciences in the early twentiescentury led to the identification of the basic principles of heredity. At the same time, terms describing the basic concepts of modern genetics were introduced into circulation. It was a "gene" and a "genome".

The term "gene" denotes a unit of hereditaryinformation, which is responsible for the formation of any property of the host organism. The transfer of genes underlies the whole process of reproduction in living nature. This term was first used by botanist Wilhelm Johansen in 1909. Today it is known that the genes are certain parts of DNA (deoxyribonucleic acid). Each gene is responsible for the transmission of information about the structure of a protein or ribonucleic acid (RNA), which, among other things, is involved in the process of cell synthesis. Usually, the gene is composed of more than one DNA region. Structures directly responsible for the transfer of hereditary information are called coding sequences. However, in DNA there are structures that affect the manifestation of the gene. Such fragments are called regulatory fragments. In other words, genes consist of coding and regulatory sequences that are located separately in the DNA. The term "genome" was introduced in 1920 by Hans Winkler. Initially, they designated a set of genes for a single unpaired set of chromosomes, inherent in the biological species. It was believed that the genome completely covers all the properties of organisms of a separate species. However, further studies have shown that this is not entirely true, therefore the meaning of the term has changed somewhat. It has been revealed that in the DNA of most organisms there are many "junk", not encoding anything sequences. In addition, some of the genetic information is contained in DNA located outside the nucleus of the cell (outside chromosomes). And also some of the genes encoding the same trait may differ in structure. Thus, by the term "genome" today is meant a certain collective set of genes contained both in chromosomes and outside them. It characterizes the properties of a certain population of individuals, but the genetic set of a particular organism can be very different from its genome.

Tip 2: What is RnK

The bodies of all living beings are made up of protein structures that perform many functions. For example, the muscles that allow movement to our bodies are built from proteins formed with the participation of RNA as a result of biosynthesis. And according to scientists, it is from RNA polymers life began on our planet.

Ribonucleic acid is a polymer that consists of nucleoside phosphate elements joined together by phosphodiester bonds. Macromolecular structure RNA basically has the form of a single-stranded chain, which inin turn, can form double-helix regions. This acid plays an important role in the process of vital activity of all living organisms, participating in the synthesis of proteins and the formation of genetic material. On television and in other media often talk about DNA and related discoveries, but rarely mention ribonucleic acid. And by the way, an interesting fact is that on Earth there are organisms that do not carry a DNA code, but contain only RNA. And, according to some scientists, the first living organisms were formed precisely from this structure. It is important to note that different types RNA in the cells of bacteria, plants and animals perform different roles. Education RNA occurs inside cells, or rather, insidecell nucleus. Under the influence of polymerases of enzymes that catalyze the formation of nucleic acids, the process of biosynthesis of ribonucleic acids takes place on the matrix of deoxyribonucleic acids. At viruses this process occurs or happens on RNA-dependent RNA-polymerization. Types RNAInformation RNA - this type of ribonucleic acids, has the longest chain length, among the others. AND-RNA plays the role of a carrier of hereditary information into the cytoplasm of the cell from its nucleus. RNA - is involved in the process of protein synthesis and is engaged in the delivery of amino acids to the ribosomes. This type RNA, like the previous one, is located in the nucleus and cytoplasm of the cell and has the shortest length - 75 nucleotides. But, despite the small length of the chain, t-RNA has the most complex structure. Ribosomal RNA - this type is contained in the nucleolus and cell ribosomes. The main function of this type RNA, is translation, catalysis and the formation of bonds between amino acids and t-RNA.

Tip 3: What is a diploid set of chromosomes

Chromosomes (from the Greek. chroma - color and soma - body) - nuclear structures of eukaryotic cells, in which most of the hereditary information is concentrated. Their function is to store, implement and transmit it.

Prokaryotes and eukaryotes

All living organisms are divided into prokaryotes andeukaryotes. The first are unicellular organisms that do not have a formed nucleus and other membrane organelles. They are also called "pre-nuclear". Eukaryotic cells contain nuclei. These include plants, animals, fungi and protists. In eukaryotic cells, the nucleus is the most important structure, which is the center of cell control and the repository of information about it. More than 90% of the cellular DNA is concentrated in the nucleus.

DNA molecules (deoxyribonucleic acid) contain hereditary information about the cell.

Where do chromosomes come from?

In the core content - karyoplasm - are locatednucleoli and chromatin. Chromatin is a protein bound to proteins. Before dividing the cell, the DNA is twisted and forms chromosomes, and the nuclear proteins-histones go to the correct DNA packing.

When laying the DNA, the volume it occupies decreases many times. Each chromosome is formed by only one DNA molecule.

What is a chromosome set

The chromosomal set of a cell is called a karyotype. It is unique for every kind of living thing. Even if the number of chromosomes coincides (for example, in chimpanzees and potatoes in cells with 48 chromosomes), their shape and structure will still be different. The somatic cells that make up the tissues of the multicellular organism contain a diploid, i.e. double set of chromosomes. Half of the chromosomes went to each cell from the maternal ovule, and half from the sperm cell. All paired chromosomes, with the exception of genital chromosomes, are absolutely identical to each other and are called homologous.

There are 23 pairs of chromosomes in the cells of the human body.

In the case of a haploid set, each chromosomeis presented in the singular. Such a set is characteristic for gametes. Thus, the ovule of a woman and the spermatozoa of a man contain 23 chromosomes, while the somatic cells contain 46.

DNA Reduplication

In preparation for cell division, each chromosomedoubles. This is due to reduplication (replication) of DNA. By breaking off the complementary nitrogen bases - adenine-thymine and guanine-cytosine - the fragment of the molecule of "maternal" DNA is disintegrated into two strands. Then, by means of the DNA polymerase enzyme, a nucleotide complementary to it is adjusted to each nucleotide of the dispersed filaments. So two new DNA molecules are formed, consisting of one chain of "mother" DNA and one newly synthesized "daughter" chain. They are completely identical.

Tip 4: What are allelic genes

The genotype includes many different genes,Acting as a single entity and responsible for certain characteristics. Diploid organisms differ from haploid by two genes responsible for each feature - these genes are called allelic. What are allelic genes and how do they interact with each other?

Allele: Definition and Concept

Allele is called one of the forms of a gene thatdetermines one of the many variants of the development of a particular trait. Typically, alleles are divided into dominant and recessive - the first fully corresponds to a healthy gene, while the recessive includes various mutations of its gene, leading to a "malfunction" in its work. There is also a multiple allelicism, in which genetics secrete more than two alleles.

With multiple alleles, diploid organisms have two alleles inherited from parents in different combinations.

An organism with the same allelic genesis considered homozygous, and the organism with different alleles is heterozygous. Heterozygote differs in the manifestation of the dominant trait in the phenotype and in the hiding of the recessive. With complete dominance, the heterozygous organism has a dominant phenotype, while under incomplete dominance, its phenotype is intermediate between a recessive and dominant allele. Thanks to a pair of homologous alleles that fall into the germ cell of the organism, the species of living beings are changeable and capable of evolution.

Interaction of allelic genes

There is only one possibility of interactionof these genes - with absolute dominance of one allele over the second, remaining in the recessive state. The basis of genetics consists of no more than two types of interaction of allelic genes - allelic and non-allelic. Since the allelic genes of each living organism are always present in the pair, their interaction can occur through a method of codomination, overdominization, and complete and incomplete dominance.

Only one pair of allelic genes is capable of manifesting phenotypic characters - while some rest, others work.

Interaction of alleles with complete dominanceoccurs only when the dominant gene completely overlaps the recessive gene. Interaction with incomplete dominance is carried out with incomplete suppression of the recessive gene, partially involved in the formation of phenotype features. Co-domination occurs with a separate manifestation of the properties of allelic genes, while overdominization is an increase in the quality of phenotypic signs of a dominant gene that is in conjunction with a recessive gene. Thus, two dominant genes that are in the same allele will manifest worse than the dominant gene, supplemented by a recessive gene.

Tip 5: Is there an alcoholism gene?

Addiction to alcohol is a painful topic for everyone.third family in Russia. Despite the ban on the sale of alcohol to persons under the age of 18, the age category of alcoholics is "younger" every year. Is alcoholism inherited and is there an alcoholism gene? Let's try to understand.

What is alcoholism?

Alcoholism is a painful dependence of a person onbeverages containing ethanol (ethyl alcohol). When alcoholism is lost taste, a person does not feel the edge of the drunk, and the doses to achieve satisfaction are required more and more.

The concept of "chronic alcoholism" was first introducedSwedish doctor M. Guss in 1849, observing a group of patients with a set of pathologies against the background of excessive consumption of alcohol. Later, scientists from different countries proved that in an unchanged form through the urinary system, only 1-10% of the alcohol intake is excreted, the remaining percentage passes through the cleavage stages and has the property of accumulating in the human body, gradually destroying the brain cells and liver cells.

Genes associated with alcohol

After taking alcohol, a four-phaseoxidation of ethanol in the liver. In the third phase, ethanol is converted to acetaldehyde, and then in the fourth phase to safe acetic acid. Scientists have identified the gene responsible for this transformation - ALDH2. People who do not have this gene in their DNA set have a high percentage of Alzheimer's disease, a memory disorder.

In May 2015, scientists at the Scripps Institute in La Hoya (USA) discovered the gene GIRK3, involved in the synthesis of protein in the body. Experiments in mice showed that the absence or damage of this gene in the body of mice forced the animals to get drunk to a critical state, and copying the gene, on the contrary, led to the fact that rodents lost interest in alcohol.

Psychological factor

Despite all the assurances of geneticists aboutexistence and transfer of the gene of alcoholism by inheritance, there are options when in the family of chronic alcoholics a child as he grows up in his whole life has never touched alcohol. We are talking about the so-called "reverse effect", when the picture of parents' drunkenness drastically exerted a strong psychological effect, and disgust for alcohol arose at a subconscious level.

However, scientists refute the psychological factorand argue that the child could simply pass "good" genes of great-grandmothers. It remains only to believe that further scientific research will help solve the problem of drinking drunkenness once and for all.

Tip 6: How is the Duchenne Dystrophy Gene transmitted?

Duchenne muscular dystrophy (DMD) is causeda violation of genes (hereditary units that are passed on to children from their parents). This disease is found only in boys, the carrier of the gene is always a woman.

Causes of Duchenne muscular dystrophy

Duchenne muscular dystrophy is characterized bya deficiency in the body of dystrophin protein, it causes deterioration of the state of muscles and their destruction, leading to a progressive difficulty in general mobility, walking. The gene of muscular dystrophy of Duchesne is transmitted as follows. This defective gene is X-linked, it is on the X chromosome. Women have two X-chromosomes, and in men - one X-chromosome, which is transmitted from the mother, and one Y-chromosome transmitted from the father. In about two-thirds of cases, the wrong gene is transmitted to the boy through the defective X-chromosome of the mother.

Duchenne muscular dystrophy is the most rapidly progressing childhood neuromuscular disease. In the world, every 3000th boy suffers from it.

In this case, the mother is considered a "carrier". She does not have symptoms of the disease, since this gene is recessive, and the second normal X chromosome is dominant, so her body will produce dystrophin in the normal amount. A very small number of carriers present a moderate degree of muscle weakness in the shoulders and hips. Such women are "manifested carriers". In about one third of the cases of the appearance of Duchenne muscular dystrophy, a genetic disorder is present only in the boy, in this case it is called a "spontaneous mutation".

What is the probability of inheriting a defective gene

Every boy born from a woman carrier,has a 50% chance of inheriting Duchenne muscular dystrophy from the defective X chromosome of the mother. Likewise, every girl born from such a woman has a 50% chance of becoming a carrier of the gene for this disease. Therefore, immediately after the diagnosis of DMD, you need to consult a geneticist on heredity. All family members who may be carriers are required to be tested. During the consultation, the doctor will provide information on the sequence of heredity, tell about the possible consequences of the disease and for other family members.

A gene disorder could have appeared in the previous generation.

Currently, Duchenne muscular dystrophy is notcured, but research in this area continues around the world. In particular, the development of the production of a synthetic gene, which can be introduced into the body, is underway. There is a technique for myoblast transplantation, when donor cells are introduced into a damaged muscle. It is assumed that they will create several normal fibers that will produce the dystrophin gene. But this method of treatment has not yet proved its effectiveness.

Tip 7: How is the hemophilia gene transmitted?

Among human diseases, a special group of hereditary diseases is distinguished, the appearance of which depends on genetic factors. The emergence of these ailments depends on the combination of genes that each person receives equally - from the father and from the mother, with some diseases transmitted regardless of the sex of the person, while others depend on sex.

All human genes are divided into dominant andrecessive, and the dominant (strong) genes always and in any combination will suppress recessive. Weak recessive genes can manifest themselves in the human genotype only when simultaneously from the father and mother the child will receive two such genes. Otherwise, with the combination of the dominant and recessive gene, the sign will not appear, but the person will be the bearer of such a "weak" gene. In addition, the sex of a person is determined by the combination of sex chromosomes, and the female sex is a combination of two XX chromosomes, while the male XY genotype is obtained if the mother receives the X chromosome and the father of the Y chromosome. Sex chromosomes, in addition to information about the future child's field, also contain data on some human diseases. Recessive genes linked to the X chromosome will only appear if the pathological gene is contained in the maternal and paternal X chromosomes of the girl, or when the boy receives the Y chromosome from his father and the pathologically altered X chromosome from mother. Its properties simply will not be blocked by the second chromosome (there are simply no such genes in the U-chromosome), therefore all sons of the latent carriers will suffer from such a disease recessively linked to the X chromosome. Such a disease is hemophilia, whose genes are in the X chromosome . Therefore, in 90% of cases, such a disease is sick boys, in the blood of which there are no special proteins that determine the processes of blood clotting. The disease itself is manifested by abundant and prolonged bleeding and hemorrhage, which occur with the slightest trauma, and in some cases even without external additional influences. Bleeding can last for hours and even days, and massive blood loss leads to disruption of all organs and systems of the patient's body, and constantly increasing in the volume of the hematoma leads to mechanical compression of tissues. The only way to treat hemophilia becomes a constant introduction into the body of specialdrugs obtained from the blood of healthy people - antihemophilic plasma and cryoprecipitate. Such therapy patients should receive throughout life, otherwise another bleeding may become fatal.

Tip 8: What is a triplet (codon)

Biosynthesis of protein is the most important process in livingorganism. Each cell contains many proteins, including those that are unique to this type of cells. Since all proteins are destroyed sooner or later, they need to be continuously restored. This process requires the expenditure of energy, the universal source of which is ATP.

What is the primary structure of the protein

The primary structure of the protein is the sequenceamino acids linked by peptide bonds, determines the whole variety of functions of these macromolecules. The information on the primary structure is contained in the nucleotide sequence.

What is called a gene and how many of them are on one chromosome

A section of DNA containing information on the structureOne protein, is a gene. In one chromosome, hundreds of genes can be located. The chromosomes themselves are chromatin strands wrapped in special proteins, like threads on a coil (a complex of proteins with chromatin). However, in the period between cell divisions, when genes function, chromatin threads are untwisted (despiralized).

How amino acids are encoded in DNA

Proteins are large polymer molecules. Their monomers are amino acids. Each amino acid in the DNA molecule corresponds to a sequence of three nucleotides - a triplet. About 20 amino acids are included in the protein composition. Each of them corresponds to its triplet combinations of DNA nucleotides, and several amino acids can encode several triplets. It is believed that such redundancy of the genetic code increases the reliability of storage and transmission of hereditary information.

Nitrogen bases - "bricks" of triplets

In the DNA molecule there are four nitrogenousBases: adenine (A), thymine (T), guanine (D) and cytosine (C). Of these, triplets are composed. The total number of possible combinations (codons) is 4 ^ 3 = 64. Thus, 64 amino acids could be encoded, but only 20 are needed. Therefore, some different combinations correspond to the same amino acid. For example, the coding triplets of the amino acid alanine are HCC, GCC, GCA and GTG. A random error in the third nucleotide does not affect the structure of the protein.

Which triplets are "punctuation marks"

One DNA molecule includes many genes. To separate them somehow, there are triplets, signaling the beginning and end of a gene - "punctuation marks." These codons are UAA, UAG, UGA. When they appear on the ribosome during the translation, the protein synthesis ends.

Important properties of the genetic code

The genetic code is specific: it means that the triplet always encodes a single amino acid, and no other. In addition, the code is universal for all living things, whether it be a bacterium or a person.

Sources:

gene gene

LovesTheTeam.com

All About Everything