§7. Hereditary information and genetic code. How and where the hereditary properties of organisms are encoded What is a chromosome? Sex chromosomes

Previously, we emphasized that nucleotides have an important feature for the formation of life on Earth - in the presence of one polynucleotide chain in a solution, the process of formation of a second (parallel) chain spontaneously occurs based on the complementary connection of related nucleotides. The same number of nucleotides in both chains and their chemical affinity are an indispensable condition for the implementation of this type of reaction. However, during protein synthesis, when information from mRNA is implemented into the protein structure, there can be no talk of observing the principle of complementarity. This is due to the fact that in mRNA and in the synthesized protein not only the number of monomers is different, but also, what is especially important, there is no structural similarity between them (nucleotides on the one hand, amino acids on the other). It is clear that in this case there is a need to create a new principle for accurately translating information from a polynucleotide into the structure of a polypeptide. In evolution, such a principle was created and its basis was the genetic code.

The genetic code is a system for recording hereditary information in nucleic acid molecules, based on a certain alternation of nucleotide sequences in DNA or RNA, forming codons corresponding to amino acids in a protein.

The genetic code has several properties.

Tripletity.

Degeneracy or redundancy.

Unambiguity.

Polarity.

Non-overlapping.

Compactness.

Versatility.

It should be noted that some authors also propose other properties of the code related to the chemical characteristics of the nucleotides included in the code or the frequency of occurrence of individual amino acids in the body’s proteins, etc. However, these properties follow from those listed above, so we will consider them there.

A. Tripletity. The genetic code, like many complexly organized systems, has the smallest structural and smallest functional unit. A triplet is the smallest structural unit of the genetic code. It consists of three nucleotides. A codon is the smallest functional unit of the genetic code. Typically, triplets of mRNA are called codons. In the genetic code, a codon performs several functions. Firstly, its main function is that it encodes a single amino acid. Secondly, the codon may not code for an amino acid, but, in this case, it performs another function (see below). As can be seen from the definition, a triplet is a concept that characterizes elementary structural unit genetic code (three nucleotides). Codon – characterizes elementary semantic unit genome - three nucleotides determine the attachment of one amino acid to the polypeptide chain.

The elementary structural unit was first deciphered theoretically, and then its existence was confirmed experimentally. Indeed, 20 amino acids cannot be encoded with one or two nucleotides because there are only 4 of the latter. Three out of four nucleotides give 4 3 = 64 variants, which more than covers the number of amino acids available in living organisms (see Table 1).

The 64 nucleotide combinations presented in table have two features. Firstly, of the 64 triplet variants, only 61 are codons and encode any amino acid, they are called sense codons. Three triplets do not encode

Table 1.

Messenger RNA codons and corresponding amino acids

FOUNDATION OF KODONOV
				Nonsense	Nonsense
				Nonsense
					Meth
					Shaft

amino acids a are stop signals indicating the end of translation. There are three such triplets - UAA, UAG, UGA, they are also called “meaningless” (nonsense codons). As a result of a mutation, which is associated with the replacement of one nucleotide in a triplet with another, a nonsense codon can arise from a sense codon. This type of mutation is called nonsense mutation. If such a stop signal is formed inside the gene (in its information part), then during protein synthesis in this place the process will be constantly interrupted - only the first (before the stop signal) part of the protein will be synthesized. A person with this pathology will experience a lack of protein and will experience symptoms associated with this deficiency. For example, this kind of mutation was identified in the gene encoding the hemoglobin beta chain. A shortened inactive hemoglobin chain is synthesized, which is quickly destroyed. As a result, a hemoglobin molecule devoid of a beta chain is formed. It is clear that such a molecule is unlikely to fully fulfill its duties. A serious disease occurs that develops as hemolytic anemia (beta-zero thalassemia, from the Greek word “Thalas” - Mediterranean Sea, where this disease was first discovered).

The mechanism of action of stop codons differs from the mechanism of action of sense codons. This follows from the fact that for all codons encoding amino acids, corresponding tRNAs have been found. No tRNAs were found for nonsense codons. Consequently, tRNA does not take part in the process of stopping protein synthesis.

CodonAUG (sometimes GUG in bacteria) not only encode the amino acids methionine and valine, but are alsobroadcast initiator .

b. Degeneracy or redundancy.

61 of the 64 triplets encode 20 amino acids. This three-fold excess of the number of triplets over the number of amino acids suggests that two coding options can be used in the transfer of information. Firstly, not all 64 codons can be involved in encoding 20 amino acids, but only 20 and, secondly, amino acids can be encoded by several codons. Research has shown that nature used the latter option.

His preference is obvious. If out of 64 variant triplets only 20 were involved in encoding amino acids, then 44 triplets (out of 64) would remain non-coding, i.e. meaningless (nonsense codons). Previously, we pointed out how dangerous it is for the life of a cell to transform a coding triplet as a result of mutation into a nonsense codon - this significantly disrupts the normal functioning of RNA polymerase, ultimately leading to the development of diseases. Currently, three codons in our genome are nonsense, but now imagine what would happen if the number of nonsense codons increased by about 15 times. It is clear that in such a situation the transition of normal codons to nonsense codons will be immeasurably higher.

A code in which one amino acid is encoded by several triplets is called degenerate or redundant. Almost every amino acid has several codons. Thus, the amino acid leucine can be encoded by six triplets - UUA, UUG, TSUU, TsUC, TsUA, TsUG. Valine is encoded by four triplets, phenylalanine by two and only tryptophan and methionine encoded by one codon. The property that is associated with recording the same information with different symbols is called degeneracy.

The number of codons designated for one amino acid correlates well with the frequency of occurrence of the amino acid in proteins.

And this is most likely not accidental. The higher the frequency of occurrence of an amino acid in a protein, the more often the codon of this amino acid is represented in the genome, the higher the likelihood of its damage by mutagenic factors. Therefore, it is clear that a mutated codon has a greater chance of encoding the same amino acid if it is highly degenerate. From this perspective, the degeneracy of the genetic code is a mechanism that protects the human genome from damage.

It should be noted that the term degeneracy is used in molecular genetics in another sense. Thus, the bulk of the information in a codon is contained in the first two nucleotides; the base in the third position of the codon turns out to be of little importance. This phenomenon is called “degeneracy of the third base.” The latter feature minimizes the effect of mutations. For example, it is known that the main function of red blood cells is to transport oxygen from the lungs to the tissues and carbon dioxide from the tissues to the lungs. This function is performed by the respiratory pigment - hemoglobin, which fills the entire cytoplasm of the erythrocyte. It consists of a protein part - globin, which is encoded by the corresponding gene. In addition to protein, the hemoglobin molecule contains heme, which contains iron. Mutations in globin genes lead to the appearance of different variants of hemoglobins. Most often, mutations are associated with replacing one nucleotide with another and the appearance of a new codon in the gene, which may encode a new amino acid in the hemoglobin polypeptide chain. In a triplet, as a result of mutation, any nucleotide can be replaced - the first, second or third. Several hundred mutations are known that affect the integrity of the globin genes. Near 400 of which are associated with the replacement of single nucleotides in a gene and the corresponding amino acid replacement in a polypeptide. Of these only 100 replacements lead to instability of hemoglobin and various kinds of diseases from mild to very severe. 300 (approximately 64%) substitution mutations do not affect hemoglobin function and do not lead to pathology. One of the reasons for this is the above-mentioned “degeneracy of the third base,” when a replacement of the third nucleotide in a triplet encoding serine, leucine, proline, arginine and some other amino acids leads to the appearance of a synonymous codon encoding the same amino acid. Such a mutation will not manifest itself phenotypically. In contrast, any replacement of the first or second nucleotide in a triplet in 100% of cases leads to the appearance of a new hemoglobin variant. But even in this case, there may not be severe phenotypic disorders. The reason for this is the replacement of an amino acid in hemoglobin with another one similar to the first in physicochemical properties. For example, if an amino acid with hydrophilic properties is replaced by another amino acid, but with the same properties.

Hemoglobin consists of the iron porphyrin group of heme (oxygen and carbon dioxide molecules are attached to it) and protein - globin. Adult hemoglobin (HbA) contains two identical -chains and two -chains. Molecule -chain contains 141 amino acid residues, -chain - 146, - And -chains differ in many amino acid residues. The amino acid sequence of each globin chain is encoded by its own gene. Gene encoding -the chain is located in the short arm of chromosome 16, -gene - in the short arm of chromosome 11. Substitution in the gene encoding -the hemoglobin chain of the first or second nucleotide almost always leads to the appearance of new amino acids in the protein, disruption of hemoglobin functions and serious consequences for the patient. For example, replacing “C” in one of the triplets CAU (histidine) with “Y” will lead to the appearance of a new triplet UAU, encoding another amino acid - tyrosine. Phenotypically this will manifest itself in a severe disease.. A similar substitution in position 63 -chain of the histidine polypeptide to tyrosine will lead to destabilization of hemoglobin. The disease methemoglobinemia develops. Replacement, as a result of mutation, of glutamic acid with valine in the 6th position -chain is the cause of the most severe disease - sickle cell anemia. Let's not continue the sad list. Let us only note that when replacing the first two nucleotides, an amino acid with physicochemical properties similar to the previous one may appear. Thus, replacement of the 2nd nucleotide in one of the triplets encoding glutamic acid (GAA) in -chain with “U” leads to the appearance of a new triplet (GUA), encoding valine, and replacing the first nucleotide with “A” forms the triplet AAA, encoding the amino acid lysine. Glutamic acid and lysine are similar in physicochemical properties - they are both hydrophilic. Valine is a hydrophobic amino acid. Therefore, replacing hydrophilic glutamic acid with hydrophobic valine significantly changes the properties of hemoglobin, which ultimately leads to the development of sickle cell anemia, while replacing hydrophilic glutamic acid with hydrophilic lysine changes the function of hemoglobin to a lesser extent - patients develop a mild form of anemia. As a result of the replacement of the third base, the new triplet can encode the same amino acids as the previous one. For example, if in the CAC triplet uracil was replaced by cytosine and a CAC triplet appeared, then virtually no phenotypic changes in humans will be detected. This is understandable, because both triplets code for the same amino acid – histidine.

In conclusion, it is appropriate to emphasize that the degeneracy of the genetic code and the degeneracy of the third base from a general biological point of view are protective mechanisms that are inherent in evolution in the unique structure of DNA and RNA.

V. Unambiguity.

Each triplet (except nonsense) encodes only one amino acid. Thus, in the direction codon - amino acid the genetic code is unambiguous, in the direction amino acid - codon it is ambiguous (degenerate).

Unambiguous

Amino acid codon

Degenerate

And in this case, the need for unambiguity in the genetic code is obvious. In another option, when translating the same codon, different amino acids would be inserted into the protein chain and, as a result, proteins with different primary structures and different functions would be formed. Cell metabolism would switch to the “one gene – several polypeptides” mode of operation. It is clear that in such a situation the regulatory function of genes would be completely lost.

g. Polarity

Reading information from DNA and mRNA occurs only in one direction. Polarity is important for defining higher order structures (secondary, tertiary, etc.). Earlier we talked about how lower-order structures determine higher-order structures. Tertiary structure and higher order structures in proteins are formed as soon as the synthesized RNA chain leaves the DNA molecule or the polypeptide chain leaves the ribosome. While the free end of an RNA or polypeptide acquires a tertiary structure, the other end of the chain continues to be synthesized on DNA (if RNA is transcribed) or a ribosome (if a polypeptide is transcribed).

Therefore, the unidirectional process of reading information (during the synthesis of RNA and protein) is essential not only for determining the sequence of nucleotides or amino acids in the synthesized substance, but for the strict determination of secondary, tertiary, etc. structures.

d. Non-overlapping.

The code may be overlapping or non-overlapping. In most organisms the code does not overlap. Overlapping code is found in some phages.

The essence of a non-overlapping code is that a nucleotide of one codon cannot simultaneously be a nucleotide of another codon. If the code were overlapping, then the sequence of seven nucleotides (GCUGCUG) could encode not two amino acids (alanine-alanine) (Fig. 33, A) as in the case of a non-overlapping code, but three (if there is one nucleotide in common) (Fig. . 33, B) or five (if two nucleotides are common) (see Fig. 33, C). In the last two cases, a mutation of any nucleotide would lead to a violation in the sequence of two, three, etc. amino acids.

However, it has been established that a mutation of one nucleotide always disrupts the inclusion of one amino acid in a polypeptide. This is a significant argument that the code is non-overlapping.

Let us explain this in Figure 34. Bold lines show triplets encoding amino acids in the case of non-overlapping and overlapping code. Experiments have clearly shown that the genetic code is non-overlapping. Without going into details of the experiment, we note that if you replace the third nucleotide in the sequence of nucleotides (see Fig. 34)U (marked with an asterisk) to some other thing:

1. With a non-overlapping code, the protein controlled by this sequence would have a substitution of one (first) amino acid (marked with asterisks).

2. With an overlapping code in option A, a substitution would occur in two (first and second) amino acids (marked with asterisks). Under option B, the replacement would affect three amino acids (marked with asterisks).

However, numerous experiments have shown that when one nucleotide in DNA is disrupted, the disruption in the protein always affects only one amino acid, which is typical for a non-overlapping code.

GZUGZUG GZUGZUG GZUGZUG

GCU GCU GCU UGC GCU GCU GCU UGC GCU GCU GCU

*** *** *** *** *** ***

Alanin - Alanin Ala - Cis - Ley Ala - Ley - Ley - Ala - Ley

A B C

Non-overlapping code Overlapping code

Rice. 34. A diagram explaining the presence of a non-overlapping code in the genome (explanation in the text).

The non-overlap of the genetic code is associated with another property - the reading of information begins from a certain point - the initiation signal. Such an initiation signal in mRNA is the codon encoding methionine AUG.

It should be noted that a person still has a small number of genes that deviate from the general rule and overlap.

e. Compactness.

There is no punctuation between codons. In other words, triplets are not separated from each other, for example, by one meaningless nucleotide. The absence of “punctuation marks” in the genetic code has been proven in experiments.

and. Versatility.

The code is the same for all organisms living on Earth. Direct evidence of the universality of the genetic code was obtained by comparing DNA sequences with corresponding protein sequences. It turned out that all bacterial and eukaryotic genomes use the same sets of code values. There are exceptions, but not many.

The first exceptions to the universality of the genetic code were found in the mitochondria of some animal species. This concerned the terminator codon UGA, which reads the same as the codon UGG, encoding the amino acid tryptophan. Other rarer deviations from universality were also found.

MZ. The genetic code is a system for recording hereditary information in nucleic acid molecules, based on a certain alternation of nucleotide sequences in DNA or RNA that form codons,

corresponding to amino acids in protein.The genetic code has several properties.

Remember what structure proteins have. What determine the structure, shape and properties of a protein molecule? Why are the proteins of each organism different from each other?

Such signs of living things as self-reproduction, heredity and variability manifest themselves already at the molecular genetic level. They are associated with certain organic substances and with the hereditary (genetic) program of the body.

DNA and genes. By the beginning of the 50s. XX century scientists have suggested that the main function of genes is to determine the structure of proteins, primarily enzyme proteins. Numerous studies have shown that most transformations of substances in living systems occur under the control of enzymes. Therefore, scientists have put forward an assumption that can be formulated as follows: “one gene - one enzyme protein.” Only the discovery of the double helix of the DNA molecule made it possible to clarify the general principles of the process of transferring genetic information in living things.

DNA molecules serve as carriers of hereditary information. They store information about the structure. properties and functions of proteins in each cell and the organism as a whole. A section of a DNA molecule containing information about the structure of one molecule of a protein-enzyme was called a genome (from the Greek genos - genus, origin). It is the hereditary factor of any living body of nature.

Genetic code. Proteins contain 20 amino acids, the sequence of which determines the structure and properties of proteins. Information about the structure of a protein must be recorded as a nucleotide sequence on DNA. The rules for translating the sequence of nucleotides in a nucleic acid into the amino acid sequence of a protein are called the genetic code (from French code - a collection of conventional abbreviations and names).

It was deciphered in the 60s. XX century as a result of a series of experiments and mathematical calculations.

A DNA molecule consists of a set of four nucleotides (A, T, G, C). If each amino acid corresponded to one nucleotide, then only 4 amino acids could be encoded. If we assume that one amino acid is encoded by a combination of two nucleotides, then in this case only 42 = 16 amino acids can be encoded. Scientists have suggested that one amino acid must be encoded by three nucleotides. This number of combinations is more than enough to encode 20 amino acids (Fig. 29). In addition, one amino acid can correspond to not one, but several such combinations.

Rice. 29. The rule for converting the nucleotide sequence in DNA into the amino acid sequence in protein

The genetic code has a number of properties (Fig. 30). The code is intertwined - each amino acid corresponds to a combination of 3 nucleotides. There are 64 such combinations - triplets (codons). Of these, 61 triplets are semantic, i.e., correspond to 20 amino acids, and 3 are meaningless stop codons that do not correspond to amino acids. They fill the gaps between genes.

Rice. 30. Some properties of the genetic code

The code is unambiguous - each triplet (codon) corresponds to only one amino acid. The code is degenerate (redundant) - there are amino acids that are encoded by more than one triplet (codon). Most often, amino acids have 2-3 triplets (codons).

The code is universal - all organisms have the same genetic code, i.e. the same amino acids in different organisms are encoded by the same triplets (codons).

The code is continuous - within the gene there are no gaps between triplets (codons).

The code is non-overlapping - the final nucleotide of one triplet (codon) cannot serve as the beginning of another.

In a certain section of the DNA molecule, the amino acid sequence of a single protein molecule is encrypted using a genetic code. Since protein synthesis occurs in the cytoplasm, and DNA molecules are located in the nucleus, a structure is needed that would copy the nucleotide sequence on DNA and transfer it to the site of protein synthesis. Messenger RNA serves as such an intermediary.

In addition to the information carrier, substances are needed that would ensure the delivery of the corresponding amino acids to the site of synthesis and determine their places in the polypeptide chain. These substances are transfer RNAs. They not only ensure the delivery of amino acids to the site of synthesis, but also their coding. Protein synthesis occurs on ribosomes, the assembly of which requires another type of nucleic acid - ribosomal RNA. Consequently, for the implementation of hereditary information in living things at the molecular genetic level, DNA molecules and all types of RNA are required.

Exercises based on the material covered

1. Why were the hereditary properties of the organism initially associated with proteins?
2. How is the protein structure encoded in a DNA molecule?
3. What is a gene?
4. What is the genetic code? Describe each of its properties.
5. What is the function of stop codons?

We all know that a person’s appearance, some habits and even diseases are inherited. All this information about a living being is encoded in genes. So what do these notorious genes look like, how do they function and where are they located?

So, the carrier of all genes of any person or animal is DNA. This compound was discovered in 1869 by Johann Friedrich Miescher. Chemically, DNA is deoxyribonucleic acid. What does this mean? How does this acid carry the genetic code of all life on our planet?

Let's start by looking at where DNA is located. A human cell contains many organelles that perform various functions. DNA is located in the nucleus. The nucleus is a small organelle, which is surrounded by a special membrane, and in which all the genetic material - DNA - is stored.

What is the structure of a DNA molecule?

First of all, let's look at what DNA is. DNA is a very long molecule consisting of structural elements - nucleotides. There are 4 types of nucleotides - adenine (A), thymine (T), guanine (G) and cytosine (C). The chain of nucleotides schematically looks like this: GGAATTCTAAG... This sequence of nucleotides is the DNA chain.

The structure of DNA was first deciphered in 1953 by James Watson and Francis Crick.

In one DNA molecule there are two chains of nucleotides that are helically twisted around each other. How do these nucleotide chains stay together and twist into a spiral? This phenomenon is due to the property of complementarity. Complementarity means that only certain nucleotides (complementary) can be located opposite each other in two chains. Thus, opposite adenine there is always thymine, and opposite guanine there is always only cytosine. Thus, guanine is complementary to cytosine, and adenine is complementary to thymine. Such pairs of nucleotides opposite each other in different chains are also called complementary.

It can be shown schematically as follows:

G - C
T - A
T - A
C - G

These complementary pairs A - T and G - C form a chemical bond between the nucleotides of the pair, and the bond between G and C is stronger than between A and T. The bond is formed strictly between complementary bases, that is, the formation of a bond between non-complementary G and A is impossible.

"Packaging" of DNA, how does a DNA strand become a chromosome?

Why do these DNA nucleotide chains also twist around each other? Why is this needed? The fact is that the number of nucleotides is huge and a lot of space is needed to accommodate such long chains. For this reason, two strands of DNA twist around each other in a helical manner. This phenomenon is called spiralization. As a result of spiralization, DNA chains are shortened by 5-6 times.

Some DNA molecules are actively used by the body, while others are rarely used. In addition to spiralization, such rarely used DNA molecules undergo even more compact “packaging.” This compact packaging is called supercoiling and shortens the DNA strand by 25-30 times!

How do DNA helices pack?

Supercoiling uses histone proteins, which have the appearance and structure of a rod or spool of thread. Spiralized strands of DNA are wound onto these “coils” - histone proteins. Thus, the long thread becomes very compactly packaged and takes up very little space.

If it is necessary to use one or another DNA molecule, the process of “unwinding” occurs, that is, the DNA strand is “unwound” from the “spool” - the histone protein (if it was wound onto it) and unwinds from the spiral into two parallel chains. And when the DNA molecule is in such an untwisted state, then the necessary genetic information can be read from it. Moreover, genetic information is read only from untwisted DNA strands!

A set of supercoiled chromosomes is called heterochromatin, and the chromosomes available for reading information are euchromatin.

What are genes, what is their connection with DNA?

Now let's look at what genes are. It is known that there are genes that determine blood type, eye color, hair, skin and many other properties of our body. A gene is a strictly defined section of DNA, consisting of a certain number of nucleotides arranged in a strictly defined combination. Location in a strictly defined DNA section means that a specific gene is assigned its place, and it is impossible to change this place. It is appropriate to make the following comparison: a person lives on a certain street, in a certain house and apartment, and a person cannot voluntarily move to another house, apartment or to another street. A certain number of nucleotides in a gene means that each gene has a specific number of nucleotides and they cannot become more or less. For example, the gene encoding insulin production consists of 60 nucleotide pairs; the gene encoding the production of the hormone oxytocin - of 370 nucleotide pairs.

The strict nucleotide sequence is unique for each gene and strictly defined. For example, the sequence AATTAATA is a fragment of a gene that codes for insulin production. In order to obtain insulin, exactly this sequence is used; to obtain, for example, adrenaline, a different combination of nucleotides is used. It is important to understand that only a certain combination of nucleotides encodes a certain “product” (adrenaline, insulin, etc.). Such a unique combination of a certain number of nucleotides, standing in “its place” - this is gene.

In addition to genes, the DNA chain contains so-called “non-coding sequences”. Such non-coding nucleotide sequences regulate the functioning of genes, help in the spiralization of chromosomes, and mark the starting and ending point of a gene. However, to date, the role of most non-coding sequences remains unclear.

What is a chromosome? Sex chromosomes

The collection of genes of an individual is called the genome. Naturally, the entire genome cannot be contained in one DNA. The genome is divided into 46 pairs of DNA molecules. One pair of DNA molecules is called a chromosome. So, humans have 46 of these chromosomes. Each chromosome carries a strictly defined set of genes, for example, chromosome 18 contains genes encoding eye color, etc. Chromosomes differ from each other in length and shape. The most common shapes are X or Y, but there are others as well. Humans have two chromosomes of the same shape, which are called pairs. Due to such differences, all paired chromosomes are numbered - there are 23 pairs. This means that there is chromosome pair No. 1, pair No. 2, No. 3, etc. Each gene responsible for a specific trait is located on the same chromosome. Modern guidelines for specialists may indicate the location of the gene, for example, as follows: chromosome 22, long arm.

What are the differences between chromosomes?

How else do chromosomes differ from each other? What does the term long shoulder mean? Let's take chromosomes of the form X. The intersection of DNA strands can occur strictly in the middle (X), or it can occur not centrally. When such an intersection of DNA strands does not occur centrally, then relative to the point of intersection, some ends are longer, others, respectively, shorter. Such long ends are usually called the long arm of the chromosome, and short ends are called the short arm. In chromosomes of the Y shape, most of the arms are occupied by long arms, and the short ones are very small (they are not even indicated in the schematic image).

The size of the chromosomes varies: the largest are chromosomes of pairs No. 1 and No. 3, the smallest chromosomes are pairs No. 17, No. 19.

In addition to their shape and size, chromosomes differ in the functions they perform. Of the 23 pairs, 22 pairs are somatic and 1 pair is sexual. What does it mean? Somatic chromosomes determine all the external characteristics of an individual, the characteristics of his behavioral reactions, hereditary psychotype, that is, all the traits and characteristics of each individual person. A pair of sex chromosomes determines a person’s gender: male or female. There are two types of human sex chromosomes: X (X) and Y (Y). If they are combined as XX (x - x) - this is a woman, and if XY (x - y) - we have a man.

Hereditary diseases and chromosome damage

However, “breakdowns” of the genome occur, and then genetic diseases are detected in people. For example, when there are three chromosomes in the 21st pair of chromosomes instead of two, a person is born with Down syndrome.

There are many smaller “breakdowns” of genetic material that do not lead to disease, but on the contrary, impart good properties. All “breakdowns” of genetic material are called mutations. Mutations leading to diseases or deterioration of the body's properties are considered negative, and mutations leading to the formation of new beneficial properties are considered positive.

However, with most of the diseases that people suffer today, it is not the disease that is inherited, but only a predisposition. For example, the father of a child absorbs sugar slowly. This does not mean that the child will be born with diabetes, but the child will have a predisposition. This means that if a child abuses sweets and flour products, he will develop diabetes.

Today, the so-called predicative medicine. As part of this medical practice, a person’s predispositions are identified (based on the identification of the corresponding genes), and then he is given recommendations - what diet to follow, how to properly alternate between work and rest so as not to get sick.

How to read the information encoded in DNA?

How can you read the information contained in DNA? How does her own body use it? DNA itself is a kind of matrix, but not simple, but encoded. To read information from the DNA matrix, it is first transferred to a special carrier - RNA. RNA is chemically ribonucleic acid. It differs from DNA in that it can pass through the nuclear membrane into the cell, while DNA lacks this ability (it can only be found in the nucleus). The encoded information is used in the cell itself. So, RNA is a carrier of encoded information from the nucleus to the cell.

How does RNA synthesis occur, how is protein synthesized using RNA?

The DNA strands from which information needs to be “read” unwind, a special “builder” enzyme approaches them and synthesizes a complementary RNA chain parallel to the DNA strand. The RNA molecule also consists of 4 types of nucleotides - adenine (A), uracil (U), guanine (G) and cytosine (C). In this case, the following pairs are complementary: adenine - uracil, guanine - cytosine. As you can see, unlike DNA, RNA uses uracil instead of thymine. That is, the “builder” enzyme works as follows: if it sees A in the DNA strand, then it attaches Y to the RNA strand, if G, then it attaches C, etc. Thus, from each active gene, during transcription, a template is formed - a copy of RNA that can pass through the nuclear membrane.

How does the synthesis of a protein encoded by a specific gene occur?

After leaving the nucleus, RNA enters the cytoplasm. Already in the cytoplasm, RNA can be embedded as a matrix into special enzyme systems (ribosomes), which can synthesize, guided by RNA information, the corresponding sequence of protein amino acids. As you know, a protein molecule consists of amino acids. How does the ribosome know which amino acid to add to the growing protein chain? This is done on the basis of a triplet code. The triplet code means that the sequence of three nucleotides of the RNA chain ( triplet, for example, GGU) code for a single amino acid (in this case glycine). Each amino acid is encoded by a specific triplet. And so, the ribosome “reads” the triplet, determines which amino acid should be added next as it reads the information in the RNA. When a chain of amino acids is formed, it takes on a certain spatial shape and becomes a protein capable of performing the enzymatic, construction, hormonal and other functions assigned to it.

Protein for any living organism is the product of a gene. It is proteins that determine all the various properties, qualities and external manifestations of genes.

Elements of the correct answer

1. Each organism is individual in its hereditary characteristics, this also applies to the structure of proteins.

2. When organs and tissues are transplanted, there is a threat of their rejection due to the incompatibility of the proteins of the donor and recipient.

Answer yourself

What is the relationship between genes and proteins in the body?

What and how does a gene code?

Elements of the correct answer

1. It is necessary that the gene responsible for the phenotypic trait be inherited by the organism.

2. The gene must be either dominant or recessive, but in this case it must be in a homozygous state.

Answer yourself

What conditions contribute to the variability of an organism?

How are variability and heredity related?

Elements of the correct answer

1. Inherited traits do not always appear; for example, a trait may be recessive and be in a heterozygous state.

2. The manifestation of phenotypic traits depends on many factors (for example, the penetrance and expressivity of genes), therefore, despite the presence of the corresponding genes, the inherited trait may not appear.

Answer yourself

What is the relationship between the genotype and phenotype of an organism?

Is it possible to determine its genotype based on the phenotype of an organism? Justify your answer.

Elements of the correct answer

1. These plants differ from each other in one feature - the shape of the seeds.

2. This trait is controlled by one pair of allelic genes.

Answer yourself

Why is crossing pea plants with yellow and smooth seeds with plants that produce green and wrinkled seeds called dihybrid?

Why does the sign of seed wrinkling not appear in the first generation of a monohybrid cross?

Elements of the correct answer

1. In first generation hybrids, only the dominant trait is manifested.

2. The recessive trait is suppressed in these hybrids.

Answer yourself

How is Mendel's first law formulated?

Why, according to Mendel's first law, in F2 (the offspring of crossing F1 hybrids) is the split approximately 3:1?

Elements of the correct answer

1. Mendel’s laws are statistical in nature, i.e. are confirmed on a large number of individuals (large statistical sample).

2. In real life, in organisms that produce a small number of descendants, there are deviations from Mendel’s laws due to statistics.

3. Possible incomplete dominance, non-allelic gene interactions.

Answer yourself

Are Mendel's laws confirmed in families with two or three children? Explain your answer.

How can we explain that children in the same family inherit different traits from their parents?

Elements of the correct answer

1. Peas are a plant with pronounced contrasting allelic characteristics.

2. Peas are a self-pollinating plant, which allows you to experiment with clean lines and artificial cross-pollination.

Answer yourself

What patterns underlie the segregation by genotype and phenotype during monohybrid crossing?

What patterns underlie the segregation by genotype and phenotype during dihybrid crossing?

What is the essence of the gamete purity hypothesis?

Elements of the correct answer

1. Donkeys and horses have different karyotypes (donkeys have 62 chromosomes, horses have 64). Horse chromosomes are not homologous to donkey chromosomes.

2. Different chromosomes in meiosis do not conjugate with each other. Therefore, hybrids - mules - are sterile.

Answer yourself

Why is the number and nucleotide composition of chromosomes considered a species characteristic of organisms?

What is the biological meaning of chromosome conjugation and crossing over?

Elements of the correct answer

1. With complete dominance, heterozygous individuals exhibit a dominant trait in their phenotype (plant with red flowers? plant with white flowers = plant with red flowers: AA x ah = Ahh;Ahh- red flowers).

2. With incomplete dominance in the heterozygous state, an intermediate phenotype appears (plant with red flowers? plant with white flowers = plant with pink flowers: AA x ah = Ahh;Ahh- pink flowers).

Answer yourself

In what cases is the intermediate nature of inheritance manifested?

Can we say that the phenomenon of incomplete dominance refutes the hypothesis of gamete purity?

Elements of the correct answer

Gametes of one organism - AB, Ab; another - AB, aB.

Answer yourself

What types of gametes does an individual with the genotype produce? SсВbКК?

Write down the results of crossing individuals heterozygous for two traits in a Punnett grid.

Elements of the correct answer

1. Test crossbreeding is carried out to establish the genotype of a certain individual - to identify a recessive gene in it.

2. To do this, an individual homozygous for the recessive gene is crossed with an individual whose genotype is unknown.

Answer yourself

Is it possible to determine the genotype of an individual based on its phenotype? Explain your answer.

How can you accurately determine the genotype of an individual?

Elements of the correct answer

1. The law is valid for genes localized on one chromosome.

2. The law is violated when homologous chromosomes cross over.

Answer yourself

Under what conditions does crossing over occur?

Between which chromosomes does crossing over not occur?

What are the causes of combinational variability?

Elements of the correct answer

1. These structures include mitochondria, chloroplasts, and the cell center.

2. These organelles contain DNA.

Answer yourself

Is there heredity that is not transmitted through the chromosomal apparatus of a cell?

What do the nucleus, mitochondria and chloroplasts have in common?

Elements of the correct answer

1. Sex is determined by a pair of sex chromosomes located in human nuclear cells.

2. For men, this pair consists of a set designated XY, among women - XX.

Answer yourself

What is homo- and heterogamety?

How does sex-linked inheritance manifest itself?

Why are there no tortoiseshell cats?

Elements of the correct answer

1. Consanguineous marriages.

2. Age of the woman giving birth to the child (38–42 years).

3. Parents work in hazardous enterprises (nuclear, chemical, etc.).

Answer yourself

What risks of increasing the frequency of hereditary diseases can you name? Explain your choice.

How does Down syndrome manifest and what are the causes of this disease?

Elements of the correct answer

1. Gene mutations affect one of the gene sections. For example, one nucleotide in a triplet may drop out or be replaced. A mutation may turn out to be neutral, or it may be harmful or beneficial.

2. Chromosomal mutations can lead to serious health consequences. They are associated with chromosome rearrangement.

3. A genomic mutation affects the genome. As a result of such a mutation, the number of chromosomes in the karyotype changes. If one or more haploid sets are added to the chromosome set, the phenomenon is called polyploidy. The phenomenon of polyploidy allows one to overcome interspecific sterility.

C2 level questions

Typically, questions on genetics are not found in USE exam papers at level C2. However, we provide tasks corresponding to this level for better understanding of genetic concepts by schoolchildren.

Elements of the correct answer

Errors were made in sentences 2, 5, 6.

Sentence 2 incorrectly indicates the number of characteristics by which the plants differed.

Proposition 5 incorrectly indicates the proportion of hybrids with yellow seeds.

In sentence 6, the characteristic of yellow color is incorrectly named.

2. 1. There is reproductive isolation between species. 2. This factor contributes to the preservation of the species as an independent evolutionary unit. 3. It is especially important that genetically distant species be isolated. 4. The possibility of crossing between them is higher than with close, related species. 5. Protection from foreign genes is achieved by: a) different periods of maturation of gametes, b) similar habitats, c) the ability of the egg to distinguish between its own and foreign sperm. 6. Interspecific hybrids are often nonviable or sterile.

Elements of the correct answer

Errors were made in sentences 3, 4, 5.

In sentence 3 there is an error in indicating the nature of the genetic proximity of species.

Proposition 4 erroneously states the probability of interbreeding between certain species.

In sentence 5, one of the factors of protection against foreign genes is incorrectly named.

3. Find errors in the given text. Indicate the numbers of the sentences in which they are allowed, explain them. 1. A gene is a section of an mRNA molecule that determines the structure of a protein and the corresponding characteristic of an organism. 2. Somatic cells contain a haploid set of chromosomes. 3. Genes that store information about one trait are located in strictly defined regions of homologous chromosomes and are called allelic. 4. Individuals that carry two allelic genes that are identical in expression and produce identical gametes are called dominant. 5. Individuals carrying allelic genes of different manifestations and, accordingly, different gametes are called heterozygous. 6. The patterns of independent inheritance of traits were established by T. Morgan.

Elements of the correct answer

Errors were made in sentences 1, 2, 4, 6.

Sentence 1 has an incorrect definition of a gene.

Sentence 2 incorrectly indicates the number of chromosomes in somatic cells.

Sentence 4 incorrectly defines dominance.

Elements of the correct answer

Errors were made in the recording of the gametes produced by the parental individuals and in the recording of one of the genotypes.

Correct the mistakes you made using the Punnett grid.

5. Find errors in the given text. Indicate the numbers of the sentences in which they are allowed, explain them. 1. Gene – a section of a chromosome that encodes information about the sequence of amino acids in one protein molecule. 2. When passed from parents to children, genes change (mutate). 3. The set of all genes of an organism is called a phenotype. 4. The totality of all external and internal characteristics of an organism is called genotype. 5. It is not so much the trait itself that is inherited as the possibility of its manifestation. 6. The implementation of the trait depends on both the genotype and the environmental conditions in which the organism is formed.

Elements of the correct answer

Errors were made in sentences 2, 3, 4.

Sentence 2 erroneously indicates the nature of the transmission of genes from parents to offspring.

Sentence 3 incorrectly defines a phenotype.

Sentence 4 gives the wrong definition of genotype.

Elements of the correct answer

1. An entry in a gene expression has letter designations.

2. The entry in the chromosomal expression is shown in letter and graphic form.

Answer yourself

Find the error in the problem statement.

In dogs, the trait of black coat color is dominant over the trait of brown coat color. When crossing two black dogs, they got black and brown puppies. In the second generation, 3 black and two brown puppies were obtained from brown parents. What are the genotypes of the first pair of parents?

Find errors in the given text.

Two sons were born into the family of retired hussar colonel Ivan Aleksandrovich Prilezhaev. The boys grew up to be energetic kids and took part in all boyish fun. However, here's the problem - one of them, Peter, suffered from hemophilia, but Stepan did not have it. The boys' mother, Polina Arkadyevna, blamed her husband for Petenka's illness. Ivan Aleksandrovich did not consider himself guilty. When the boys grew up, according to tradition, they had to go serve in the hussar regiment. However, both were rejected for medical reasons, telling their father that the boys had severe heredity and could not be served. Any scratch is dangerous for both, and even more so an injury. After some time, Peter married a healthy girl with hemophilia, in whose family there were no hereditary diseases. They had two boys and two girls. All children suffered from hemophilia. Stepan also married his second daughter from the same family. He gave birth to a hemophiliac boy and two healthy girls. Nothing is known about the health of the grandchildren in this family.

What process is shown in the picture? Label the resulting gametes and explain the reason for the appearance of different gametes.

C6 level questions

Monohybrid crossing problems

Algorithm for solving problems in genetics

1. Select the letter designations of the alleles.

2. Write down all the given conditions of the problem.

3. Write the genotypes of the crossed individuals.

4. Write the types of gametes produced by parents.

5. Record the genotypes and phenotypes of the offspring.

The most important condition for correctly solving a problem is a complete understanding of what is known and what is being asked. For example, if the condition says that 9 mice were obtained from two gray mice, of which one or two were white, then this means that both parents were heterozygous for the dominant trait of gray color, and white coat color is a recessive trait. This example shows how, based on the conditions of the problem, output the data necessary to solve it. Having understood the meaning of the problem and received additional data from its conditions, correctly record the solution. In the above problem, the entry will look like this:

If the problem does not ask about the splitting of traits in the offspring according to the ratio, then you don’t need to show it. It is enough to present all possible genotypes in F1.

Examples of simple problems

1. What F1 offspring can be expected from crossing a red-flowered heterozygous pea plant ( A) with a white-flowered plant? Will there be a splitting of characteristics and in what proportion?

2. From Drosophila flies with normal wings and flies with shortened wings, flies with normal and shortened wings were obtained in a 1:1 ratio. Determine the genotypes of parents and offspring.

3. The black plumage of Andalusian chickens is not completely dominant over the white plumage. A rooster with black feathers was crossed with a hen with white feathers. Some of the chickens born from this crossing had blue plumage. Write down the genotypes of all individuals mentioned in the condition. What kind of genotype and phenotype splitting should be expected in the offspring from these parents, provided that there are quite a lot of chickens? Is it possible to breed a pure line of chickens with blue feathers?

4. When crossing two tall ( WITH) plants, 25% of the seeds were obtained, from which stunted plants grew. What are the genotypes of low-growing plants?

Dihybrid crossing problems

When solving problems of this type it is necessary:

a) carefully read the conditions of the task;
b) make the necessary notes as you read the task;
c) having understood the condition of the problem, you need to designate the alleles with the corresponding letters, draw a Punnett grid and fill it in in accordance with the logic of the solution;
d) ensure that the general form of the decision record meets the requirements.

An example of a problem covered in textbooks

Pea plants producing yellow ( A) smooth ( IN) seeds, crossed with plants that produce green ( A) wrinkled ( b) seeds. Both lines were clean. What will the hybrid offspring in F1 and F2 be like in terms of genotypes and phenotypes?

The logic of the reasoning is as follows.

1. If the lines are pure, it means that the parents are homozygous for both traits.

2. Each parent produces one type of gamete.

Genotype AABB gives gametes AB.
Genotype aabb gives gametes ab.
Therefore, all first generation hybrids will have the genotype AaBb.
Individuals with this genotype form 4 types of gametes: AB, aB, Ab, ab.

3. To determine the genotypes of individuals of the second generation, it is necessary to draw a Punnett grid and write down the types of gametes formed by the parents in the upper horizontal row and the left vertical column. After that, write down the resulting genotypes of the offspring in the remaining free fields.

	AABB and. Ch.	AaBB and. Ch.	AABb and. Ch.	AABb and. Ch.
	AaBB and. ch	aaBB h. Ch.	AaBb and. Ch.	aaBb h. Ch.
	AABb and. ch	AaBb and. Ch.	ААbb and. wrinkle	Ааbb and. wrinkle
	AaBb and. Ch.	aaBb h. Ch.	Ааbb and. wrinkle	aabb h. wrinkle

– both dominant genes;
– dominant gene of one of the traits;
– a dominant gene for another trait;
– only recessive genes.

The result in this case will be as follows: 9 AB : 3Ab : 3aB : 1ab.

5. Answer: hybrid offspring in F1 – AaBb, in the second generation there will be 16 genotypes (shown in a Punnett lattice) and 4 phenotypes:

– plants with yellow smooth seeds;
– plants with yellow wrinkled seeds;
– plants with green smooth seeds;
- plants with green wrinkled seeds.

Problems found in exam papers

Elements of the correct answer

To make a correct decision, you need to prove that:

1) flies with a genotype XY(males) can be red-eyed or white-eyed;
2) heterozygous females are always red-eyed, females homozygous for a recessive trait are white-eyed, and females homozygous for a dominant trait are red-eyed.

To prove these two points, it is necessary to cross a red-eyed heterozygous female with a white-eyed male. Some of the males resulting from this cross will have white eyes. Therefore, the recessive trait is linked to X-chromosome.

2. Make a diagram to illustrate the text below, showing the genotypes and patterns of inheritance of color blindness. If a woman suffering from color blindness marries a man with normal vision, then their children exhibit a very peculiar pattern of cross-inheritance. All daughters from such a marriage will receive the sign of their father, i.e. they have normal vision, and all sons, receiving the mother’s trait, suffer from color blindness (a-color blindness linked to X-chromosome). In the same case, when the father is color blind and the mother has normal vision, all children turn out to be normal. In some marriages in which the mother and father have normal vision, half of the sons may be affected by color blindness. Color blindness is more common in men.

Elements of the correct answer

Girls are carriers, boys are colorblind.

Girls are carriers, boys are healthy.

Half of the boys and girls are healthy, half of the girls are carriers, half of the boys are color blind.

Elements of the correct answer for independent decision

1. Write down the letter designations of the alleles of the parents’ genotypes and the crossing scheme.

2. Determine all genotypes specified in the condition.

3. Draw up a diagram of a new crossing and write down its results.

Elements of the correct answer

1. Genotypes of parents X f X And XY.

2. Genotypes of children X f Y, X f X, XX, XY.

3. The nature of inheritance is dominant, linked to X-chromosome.

Elements of the correct answer

1. According to the condition, the baldness gene was inherited only by boys.

2. All women in the families in question had normal hair.

3. Consequently, this gene was passed on from fathers, i.e. in the male line.

4. Conclusion: the sign is linked to U-chromosome and is passed on from fathers to sons.

P1 XY l x XX
F1 2 XY l and 4 XX
P2 XY l x XX
F2 Grandchildren XY l

Decide for yourself

Make a diagram to illustrate the text below, showing the genotypes and patterns of inheritance of hemophilia.

An example of sex-linked inheritance is the inheritance of a recessive semi-lethal gene that causes blood to clot in air - hemophilia. This disease appears almost exclusively in boys. In hemophilia, the formation of a factor that accelerates blood clotting is impaired. The recessive gene that controls the synthesis of this factor is located in a certain region X-chromosome and does not have an allele in U-chromosome. After solving the problem, answer the question: “Why are women with hemophilia extremely rare?”
Write down the results of crossbreeding that can be obtained in the following cases:

a) father is a hemophiliac, mother is a carrier of the hemophilia gene;
b) the father is healthy, the mother is a carrier of the hemophilia gene;
c) the father is hemophiliac, the mother does not carry the hemophilia gene.

In humans, large eyes and a Roman (humped) nose dominate over small eyes and a Greek (straight) nose. A woman with big eyes and a Greek nose married a man with small eyes and a Roman nose. They had four children, two of whom had big eyes and a Roman nose. What are the genotypes of the parents? What is the likelihood of this couple having a child with small eyes and a Roman nose? What is the likelihood of this couple having a child with small eyes and a Greek nose?

The opening of an inheritance case is carried out by a notary when relatives of the deceased testator or testator contact him, and they provide evidence of his death. In fact, opening a inheritance case is the duty and one of the main functions of a notary. Before starting the formation of the inheritance case, the notary determines the time and place of opening the inheritance, attaching documents according to these procedures to the set of documents that make up it.

How to determine the moment of opening, where and how should the inheritance case be opened after death?

Procedures related to the opening of inheritance by law or by will are regulated by Articles 1110, 1113, 1153, 1162, 1115, 1154-55 of the civil legislation. Heirs should understand that these notarial actions will be performed by the notary only after he receives the application, as well as proof of the death of the testator.

The first question that potential heirs face is how to find out which notary is handling the inheritance matter or which notary should be contacted to carry out all inheritance procedures.

In this case, the presence or absence of a will matters. So, if there is a will, its opening is carried out by the notary who certified it. Otherwise, :

• in the notary office at the place of permanent residence;
• the presence of the testator or the bulk of the deceased’s property, which is determined by its value.

Finding a place to open an inheritance and a notary serving heirs

Before contacting a notary’s office, heirs need to prepare a number of documents:

• Document on the death of the testator;
• Evidence of relationship;
• A copy of the will, if available;
• A certificate from the deceased’s last place of residence;
• Documents for inherited property;
• Passports of heirs.

Returning to the question of how to find a notary serving the place where the inheritance is opened, it is worth explaining that information about all notaries working in the country is presented on the website of the Federal Notary Chamber - notariat.ru. Here on the main page there is a “find a notary” tab. Without information about a notary, you can search for notaries in a specific region or region in the “find a notary office” tab. As a rule, the case is opened by a notary at the place of opening of the inheritance, that is, at the place of last registration of the deceased testator.

The notary opens the case after the heir submits an application.

What documents and certificates will be needed?

The basis for carrying out notarial procedures when an inheritance is opened after death, both for opening and for forming a case, are the documents provided by the heirs. So, to the notary office at the place where the inheritance case is opened, potential heirs submit:

• Application for opening of inheritance procedures;
• Certificates from the last place of residence of the deceased relative;
• Extracts from real estate registers confirming the rights of the deceased to the property at his disposal, if there are several of them, then for each separately;
• Owner's certificates for vehicles;
• Certificates of bank accounts, securities and pension funds.

Supporting documents must be attached for the entire property indicated in the application. They can be sent by mail or delivered in person.

The procedure for a notary to conduct a case: how to open and complete it?

Opening an inheritance is the most important function of notary offices in ensuring the rights of citizens to inherit. Article 1154 defines the time frame within which the heirs must assume their rights. How soon can you enter into an inheritance? During this period, an inheritance case is also opened.

The final decision can be made after six months, that is, the inheritance case is open, but not completed. This is due to the peculiarities of the inheritance case itself, for example, if it is initiated in favor of each other or controversial issues have arisen. Notary services are not free. How much does it cost to open an inheritance case with a notary?

The very procedure of the notary's actions in preparing all documentation is regulated by the Rules of Notarial Office Work:

• Receiving applications from heirs with accompanying documents;
• Their registration and issuance by a notary of a certificate of opening of an inheritance case;
• Formation of an inventory of the property mass;
• Taking measures to ensure the safety of the inheritance and its integrity;
• Other relatives and legal heirs are duly notified that an inheritance case has been opened;
• The authenticity of the submitted documents is verified.

The documents on the basis of which a case is opened are registered in the notary's office in the case book on the date of their receipt. Next, they are placed in a folder with the case, which is assigned a number in order, indicating the year of opening. After this, the case must also be registered in the Alphabet Book and entered in.

After completion of all notarial procedures, the original document, which became the basis for the formation of the case, is returned to the heirs against a receipt, the latter is filed in the case. Also, all documents included in the inheritance file and attached to it are entered into the accounting book.

The heirs have the right to instruct the notary to ensure measures to preserve the property included in the estate. This application is also subject to registration in a special journal for recording statements and instructions, after which it is also included in the case.

Should a notary find legal heirs?

Notifying other relatives who may claim the inheritance or who have legal inheritance rights is the responsibility of the notary's office.

The notary identifies such relatives:

• requesting information either from relatives who have applied for the opening of an inheritance;
• by sending official requests to the place of residence of the testator.

The written notice indicates the details of the notary and the notary's office for the application, so that the heirs do not decide how to identify a notary for inheritance, and do not take measures to re-open the inheritance case.

Additional information about the place and moment of opening the inheritance in this video:

As a rule, if no disputes arise between the heirs, within six months they receive the appropriate certificate and take possession and use of the inherited property. The notary has the right to consider the case completed and transfer it to temporary storage.