Choose two correct answers out of five and write down the numbers under which they are indicated. The genealogical method is used to
1) obtaining gene and genomic mutations
2) studying the influence of education on human ontogenesis
3) studies of human heredity and variability
4) studying the stages of evolution of the organic world
5) identification of hereditary diseases in the family
Explanation.
The essence of the genealogical method is to clarify family ties and trace the manifestation of a certain characteristic (for example, a disease) in different generations of relatives.
Answer: 35.
Answer: 35
Establishment of correspondence between examples and views of mu-ta-tions: to each position given in the translation in the second column, under the corresponding position from the second column.
Write down the numbers in response, arranging them in a row corresponding to the letter:
| A | B | IN | G | D | E |
Clarification.
Chro-mo-some mu-ta-tions connected with na-ru-she-ni-em struk-tu-ry chro-mo-som. These developments may be associated with morning-that part-ka chro-mo-so-we(de-le-tion), doubling the area of chro-mo-so-we(du-pl-ka-tion), in-ro-that part of the chro-mo-so-we at 180 degrees(inversion), about the parts between the non-mo-lo-gich-ny chro-mo-so-ma-mi(trans-lo-ka-tion) or merging two non-mo-lo-gic chro-mo-somes in one.
Genomic mutation associated with because of the number of chromosomes in ka-ri-o-ti-pe. Types of genetic mutation: ane-up-lo-i-dia(changing the number of chromosomes into one, two or several) and po-lip-lo-i-dia(increase in the number of chromosomes, a multiple of ha-p-lo-id-no-mu na-bo-ru). Genomic mutations are associated with the same races of chromosomes at the time of cell de-letion, mainly in the mei-o-ze.
(A) once-in-the-mouth part of the chro-mo-so-we - chro-mo-som-naya mu-ta-tion(inversion);
(B) doubling of one of the chromosomes - genetic mutation(ane-up-lo-i-dia);
(B) non-dissimilarity of chro-mo-somes in mei-o-ze - genetic mutation;
(D) the birth of a child with three XXY - genetic mutation(ane-up-lo-i-dia);
(D) po-lip-lo-i-dia - genetic mutation;
(E) exchange of parts between ne-go-mo-lo-gich-ny chro-mo-so-ma-mi - chro-mo-som-naya mu-ta-tion(translocation).
Answer: 122221
Answer: 122221
Establish a correspondence between the characteristics of the mutation and its type.
Write down the selected numbers in the table under the corresponding letters.
| A | B | IN | G | D | E |
Explanation.
Mutations (disorders of hereditary information) are divided into genomic(change in the number of chromosomes in a cell), chromosomal(change in chromosome structure) and genetic(rearrangements of individual genes associated with changes in the structure of the DNA molecule and its nucleotide sequence).
(A) - inclusion of extra nucleotides in DNA → change in the nucleotide sequence of the gene → gene mutation;
(B) - multiple increase in the number of chromosomes in a cell → change in the number of chromosomes → genomic mutation;
(B) - a violation of the amino acid sequence in a molecule is the result of the nucleotide sequence of the gene → gene mutation;
(D) - rotation of a chromosome section by 180 degrees (inversion) → change in the structure of the chromosome (the order of genes in the chromosome) → chromosomal mutation;
(D) - decrease in the number of chromosomes in a somatic cell → change in the number of chromosomes → genomic mutation;
(E) - exchange of sections of non-homologous chromosomes (translocation) → change in chromosome structure(gene composition of a chromosome) → chromosomal mutation.
Answer: 232131.
Answer: 232131
Establish a correspondence between the characteristics of the mutation and its type.
Write down the numbers in your answer, arranging them in the order corresponding to the letters:
| A | B | IN | G | D |
Explanation.
Mutations (disorders of hereditary information) are divided into genomic(change in the number of chromosomes in a cell), chromosomal(change in chromosome structure) and genetic(rearrangements of individual genes associated with changes in the structure of the DNA molecule and its nucleotide sequence).
(A) - change in the nucleotide sequence in a DNA molecule → gene mutation;
(B) - change in chromosome structure → chromosomal mutations;
(B) - change in the number of chromosomes in the nucleus → genomic mutation;
(D) - polyploidy - an increase in the number of chromosomes that is a multiple of the haploid set → genomic mutation;
(D) - change in the sequence of gene location (can occur as a result of inversion - rotation of a chromosome section by 180 degrees) → chromosomal mutation.
Answer: 12332.
Answer: 12332
Source: Unified State Examination in Biology 05/30/2013. Main wave. Siberia. Option 4.
It is possible for breeders to obtain polyploid wheat varieties due to mutation
1) cytoplasmic
3) chromosomal
4) genomic
Explanation.
Polyploid organisms have an increased number of chromosomes, this genomic mutations.
Genomic mutations are mutations that lead to the addition or loss of one, several or a complete haploid set of chromosomes. Polyploidy is a multiple change in the number of chromosomes.
Chromosomal mutations are a type of mutation that changes the structure of chromosomes. They are classified as: deletions (loss of a chromosome section), inversions (change in the reverse order of the genes of a chromosome section), duplications (repetition of a chromosome section), translocations (transfer of a chromosome section to another).
Gene mutations are mutations that result in changes in individual genes and the appearance of new alleles. Gene mutations are associated with changes that occur within a given gene and affect part of it. Usually this is the replacement of nitrogenous bases in DNA, the insertion of an extra pair, or the loss of a base pair.
Cytoplasmic mutations are changes in the DNA of mitochondria and plastids. Transmitted only by female line, because mitochondria and plastids from sperm do not enter the zygote.
Answer: 4
| A | B | IN | G | D | E |
Explanation.
Mutational variability - one of the types hereditary variabilitygene mutations), chromosome structures ( chromosomal mutations) or number of chromosomes ( genomic mutations). Mutations and associated mutational variability occur in a specific individual ( individual changes), arise spontaneously
Modification variability - This non-hereditary variability, with which changes in phenotype within the normal range of reaction without changing the genotype. Modification variability occurs in response to changes in conditions environment (adaptive, adaptable nature), calling identical changes in phenotype in all individuals of the species under these specific conditions.
mutational variability;
(B) - changes within the normal range of reaction - modification variability;
(B) - changes are random - mutational variability;
(D) - changes affect genetic material - mutational variability;
(D) - always due to the influence of factors - modification variability.
Answer: 12112
Answer: 12112
Establish a correspondence between the characteristics and forms of variability: for each position given in the first column, select the corresponding position from the second column.
Write down the numbers in your answer, arranging them in the order corresponding to the letters:
| A | B | IN | G | D |
Explanation.
Mutational variability - variety hereditary variability, which is based on changes in the genotype associated with violations of the nucleotide sequence of genes ( gene mutations), chromosome structures ( chromosomal mutations) or number of chromosomes ( genomic mutations). Mutations and associated mutational variability occur in a specific individual ( individual changes), arise spontaneously, and not as a response to changes in environmental conditions.
Combinative variability - a type of hereditary variability that occurs during sexual reproduction as a result of recombination of parental genes and offspring in the process: 1) crossing over- exchange of sections between homologous chromosomes (in prophase I of meiosis during gametogenesis); 2) independent chromosome segregation during meiosis; 3) random combination of gametes during fertilization.
(A) - can be genetic, chromosomal and genomic - mutational variability;
(B) - caused by a random combination of chromosomes during fertilization - combinative variability;
(B) - may occur due to disturbances in meiosis - mutational variability;
(D) - ensured by recombination of genes during crossing over - combinative variability;
(D) - occurs when the genetic material is accidentally changed - mutational variability.
Answer: 12121
Answer: 12121
A change in the sequence of nucleotides in a DNA molecule is a mutation
2) genomic
3) chromosomal
4) autosomal
Explanation.
Gene mutations occur in DNA and are associated with changes in the composition of nucleotides in a gene.
Genomic mutations are mutations that lead to the addition or loss of one, several or a complete haploid set of chromosomes (aneuploidy, or polyploidy)
Chromosomal mutation is a type of mutation that changes the structure of chromosomes. Classify: deletions (loss of a chromosome section), inversions (change in the reverse order of the genes of a chromosome section), duplications (repetition of a chromosome section), translocations (transfer of a chromosome section to another)
Answer: 1
Natalia Evgenievna Bashtannik
No. A change in the nucleotide sequence is a point or gene mutation.
Chromosomal mutations are those that change the structure of chromosomes.
All terms below are used to describe mutational variability. Identify two terms that “fall out” from the general list and write down the numbers under which they are indicated in the table
2) chromosomal
3) combinative
4) genomic
5) modification
Explanation.
Mutational variability – a type of hereditary variability caused by a violation of the gene structure ( gene mutation), chromosome structure ( chromosomal mutation) or their quantity ( genomic mutation).
Terms (3) and (5) "drop out": (3) - combinative- another type of hereditary variability, in which hereditary information is not disrupted, but different combinations of genes are formed; (5) modification variability- non-hereditary (phenotypic) variability, in which only the phenotype changes, and the genotype remains constant.
Answer: 35
Answer: 35
All but two of the characteristics below are used to describe genomic variation. Find two characteristics that “fall out” from the general series and write down the numbers under which they are indicated.
1) accompanied by a multiple change in the number of chromosomes
2) leads to an increase in the number of haploid sets of chromosomes of one species
3) manifests itself within the normal reaction range of the trait
4) is of a group nature
5) leads to the addition or loss of a sex chromosome
Explanation.
Genomic variability associated with genomic mutations- any changes in the number of chromosomes in the genome (karyotype), both with the addition or loss of individual chromosomes (aneuploidy), and with an increase in the number of chromosomes that is a multiple of the haploid set (polyploidy). Changes in the number of chromosomes are associated with nondisjunction of homologous chromosomes of one or more pairs during cell division.
Subsequence nuclear DNA for any two people it is almost 99.9% identical. Only a very small fraction of the DNA sequence varies between individuals, providing genetic variation. Some differences in DNA sequence have no effect on phenotype, while others are direct causes of disease. Between the two extremes are changes responsible for genetically determined phenotypic variation in anatomy and physiology, food tolerance, response to treatment, or side effects medications, susceptibility to infections, susceptibility to tumors, and perhaps even variability in various features personality, athletic ability and artistic talent.
One of the important concepts of human genetics and medical genetics - that genetic diseases are only the most obvious and often extreme manifestation of genetic differences, one end of a continuum of variations from rare variants, causing disease, through more common options, increasing susceptibility to disease, to the most frequent changes that do not have obvious relationship to illness.
Types of mutations in humans
Any change in the nucleotide sequence or arrangement of DNA. Mutations can be classified into three categories: those that affect the number of chromosomes in a cell (genomic mutations), those that change the structure of individual chromosomes (chromosomal mutations), and those that change individual genes (gene mutations). Genomic mutations are changes in the number of intact chromosomes (aneuploidy) resulting from errors in chromosome segregation in meiosis or mitosis.
Chromosomal mutations- changes affecting only part of the chromosome, such as partial duplications, deletions, inversions and translocations, which can occur spontaneously or arise due to abnormal segregation of translocated chromosomes during meiosis. Gene mutations are changes in the DNA sequence of the nuclear or mitochondrial genome, ranging from mutations in a single nucleotide to changes spanning many millions of base pairs. Many types of mutations are represented by a variety of alleles at individual loci in more than a thousand different genetic diseases, as well as among the millions of DNA variants found throughout the genome in the normal population.
Description of different mutations not only increases awareness of human genetic diversity and the fragility of the human genetic heritage, but also promotes the information needed to detect and screen for genetic diseases in specific families at risk and also, for some diseases, in the population as a whole.
Genomic mutation, resulting in the loss or duplication of an entire chromosome, changes the dosage and thus the expression level of hundreds or thousands of genes. Likewise, a chromosomal mutation that affects most of one or more chromosomes can also affect the expression of hundreds of genes. Even a small gene mutation can have large consequences, depending on which gene is affected and what the change in expression of that gene causes. A gene mutation in the form of a change in a single nucleotide in the coding sequence can lead to a complete loss of gene expression or the formation of a protein with altered properties.
Some DNA changes, however, do not have phenotypic effects. A chromosomal translocation or inversion may not affect a critical part of the genome and may have absolutely no phenotypic effects. A mutation within a gene may have no effect because it either does not change the amino acid sequence of the polypeptide or, even if it does, the change in the encoded amino acid sequence does not change the functional properties of the protein. Therefore, not all mutations have clinical consequences.
All three types of mutations occur with significant frequency in many different cells. If a mutation occurs in the DNA of germ cells, it can be passed on to subsequent generations. In contrast to this, somatic mutations occur randomly only in some cells of certain tissues, leading to somatic mosaicism, observed, for example, in many tumors. Somatic mutations cannot be passed on to subsequent generations.
Almost any change in the structure or number of chromosomes, in which the cell retains the ability to reproduce itself, causes a hereditary change in the characteristics of the organism. According to the nature of the genome change, i.e. sets of genes contained in a haploid set of chromosomes, gene, chromosomal and genomic mutations are distinguished. hereditary mutant chromosomal genetic
Gene mutations are molecular changes in the structure of DNA that are not visible in a light microscope. Gene mutations include any changes in the molecular structure of DNA, regardless of their location and effect on viability. Some mutations have no effect on the structure or function of the corresponding protein. Another (large) part of gene mutations leads to the synthesis of a defective protein that is unable to perform its inherent function.
Based on the type of molecular changes, there are:
Deletions (from the Latin deletio - destruction), i.e. loss of a DNA segment from one nucleotide to a gene;
Duplications (from the Latin duplicatio doubling), i.e. duplication or reduplication of a DNA segment from one nucleotide to entire genes;
Inversions (from the Latin inversio - inversion), i.e. a 180-degree rotation of a DNA segment ranging in size from two nucleotides to a fragment including several genes;
Insertions (from the Latin insertio - attachment), i.e. insertion of DNA fragments ranging in size from one nucleotide to an entire gene.
It is gene mutations that cause the development of most hereditary forms of pathology. Diseases caused by such mutations are called gene or monogenic diseases, i.e. diseases the development of which is determined by a mutation of one gene.
The effects of gene mutations are extremely varied. Most of them do not appear phenotypically because they are recessive. This is very important for the existence of the species, since most newly occurring mutations are harmful. However, their recessive nature allows them long time persist in individuals of the species in a heterozygous state without harm to the body and appear in the future upon transition to a homozygous state.
Currently, there are more than 4,500 monogenic diseases. The most common of them are: cystic fibrosis, phenylketonuria, Duchenne-Becker myopathies and a number of other diseases. Clinically, they manifest themselves as signs of metabolic disorders (metabolism) in the body.
At the same time, there are a number of cases where a change in only one base in a certain gene has a noticeable effect on the phenotype. One example is the genetic abnormality of sickle cell anemia. The recessive allele, which causes this hereditary disease in the homozygous state, is expressed in the replacement of just one amino acid residue in the B-chain of the hemoglobin molecule ( glutamic acid? ?> valine). This leads to the fact that in the blood red blood cells with such hemoglobin are deformed (from round to sickle-shaped) and quickly destroyed. In this case, acute anemia develops and a decrease in the amount of oxygen carried by the blood is observed. Anemia causes physical weakness, problems with the heart and kidneys, and can lead to early death people homozygous for the mutant allele.
Chromosomal mutations are the causes of chromosomal diseases.
Chromosomal mutations are structural changes individual chromosomes, usually visible under a light microscope. A chromosomal mutation involves a large number (from tens to several hundreds) of genes, which leads to a change in the normal diploid set. Although chromosomal aberrations generally do not change the DNA sequence of specific genes, changes in the copy number of genes in the genome lead to genetic imbalance due to a lack or excess of genetic material. There are two large groups chromosomal mutations: intrachromosomal and interchromosomal (see Fig. 2).
Intrachromosomal mutations are aberrations within one chromosome (see Fig. 3). These include:
Deletions are the loss of one of the chromosome sections, internal or terminal. This can cause a disruption of embryogenesis and the formation of multiple developmental anomalies (for example, a deletion in the region of the short arm of the 5th chromosome, designated 5p-, leads to underdevelopment of the larynx, heart defects, mental retardation. This symptom complex is known as the “cry of the cat” syndrome, because in sick children, due to an anomaly of the larynx, crying resembles a cat’s meow);
Inversions. As a result of two points of chromosome breaks, the resulting fragment is inserted into its original place after a rotation of 180 degrees. As a result, only the order of the genes is disrupted;
Duplications are the doubling (or multiplication) of any part of a chromosome (for example, trisomy on the short arm of chromosome 9 causes multiple defects, including microcephaly, delayed physical, mental and intellectual development).
Rice. 2.
Interchromosomal mutations, or rearrangement mutations, are the exchange of fragments between non-homologous chromosomes. Such mutations are called translocations (from the Latin trans - for, through and locus - place). This:
Reciprocal translocation - two chromosomes exchange their fragments;
Non-reciprocal translocation - a fragment of one chromosome is transported to another;
? “centric” fusion (Robertsonian translocation) is the joining of two acrocentric chromosomes in the region of their centromeres with the loss of short arms.
When chromatids are transversely broken through centromeres, “sister” chromatids become “mirror” arms of two different chromosomes containing the same sets of genes. Such chromosomes are called isochromosomes.
Rice. 3.
Translocations and inversions, which are balanced chromosomal rearrangements, do not have phenotypic manifestations, but as a result of segregation of rearranged chromosomes in meiosis, they can form unbalanced gametes, which will lead to the emergence of offspring with chromosomal abnormalities.
Genomic mutations, like chromosomal ones, are the causes of chromosomal diseases.
Genomic mutations include aneuploidies and changes in the ploidy of structurally unchanged chromosomes. Genomic mutations are detected by cytogenetic methods.
Aneuploidy is a change (decrease - monosomy, increase - trisomy) in the number of chromosomes in a diploid set, not a multiple of the haploid one (2n+1, 2n-1, etc.).
Polyploidy is an increase in the number of sets of chromosomes, a multiple of the haploid one (3n, 4n, 5n, etc.).
In humans, polyploidy, as well as most aneuploidies, are lethal mutations.
The most common genomic mutations include:
Trisomy - the presence of three homologous chromosomes in the karyotype (for example, the 21st pair in Down syndrome, the 18th pair in Edwards syndrome, the 13th pair in Patau syndrome; for sex chromosomes: XXX, XXY, XYY);
Monosomy is the presence of only one of two homologous chromosomes. With monosomy for any of the autosomes, normal development of the embryo is not possible. The only monosomy in humans that is compatible with life - monosomy on the X chromosome - leads to Shereshevsky-Turner syndrome (45,X).
The reason leading to aneuploidy is the nondisjunction of chromosomes during cell division during the formation of germ cells or the loss of chromosomes as a result of anaphase lag, when during movement to the pole one of the homologous chromosomes may lag behind other non-homologous chromosomes. The term nondisjunction means the absence of separation of chromosomes or chromatids in meiosis or mitosis.
Chromosome nondisjunction most often occurs during meiosis. The chromosomes that would normally divide during meiosis remain joined together and move to one pole of the cell in anaphase, thus producing two gametes, one with an extra chromosome and the other without that chromosome. When a gamete with a normal set of chromosomes is fertilized by a gamete with an extra chromosome, trisomy occurs (i.e., there are three homologous chromosomes in the cell); when a gamete without one chromosome is fertilized, a zygote with monosomy occurs. If a monosomic zygote is formed on any autosomal chromosome, then the development of the organism stops at the very early stages development.
According to the type of inheritance they distinguish dominant And recessive mutations. Some researchers identify semi-dominant and codominant mutations. Dominant mutations are characterized by a direct effect on the body, semi-dominant mutations mean that the heterozygous form is intermediate in phenotype between the AA and aa forms, and codominant mutations are characterized by the fact that heterozygotes A 1 A 2 show signs of both alleles. Recessive mutations do not appear in heterozygotes.
If a dominant mutation occurs in gametes, its effects are expressed directly in the offspring. Many mutations in humans are dominant. They are common in animals and plants. For example, a generative dominant mutation gave rise to the Ancona breed of short-legged sheep.
An example of a semi-dominant mutation is the mutational formation of the heterozygous form Aa, intermediate in phenotype between the organisms AA and aa. This occurs in the case of biochemical traits when the contribution to the trait of both alleles is the same.
An example of a codominant mutation is the alleles I A and I B, which determine blood group IV.
In the case of recessive mutations, their effects are hidden in diploids. They appear only in the homozygous state. An example is recessive mutations that determine gene diseases person.
Thus, the main factors in determining the probability of manifestation of a mutant allele in an organism and population are not only the stage of the reproductive cycle, but also the dominance of the mutant allele.
Direct mutations? These are mutations that inactivate wild-type genes, i.e. mutations that change the information encoded in DNA in a direct way, resulting in a change from the original (wild) type organism to a mutant type organism.
Back mutations represent reversions to the original (wild) types from mutants. These reversions are of two types. Some of the reversions are caused by repeated mutations of a similar site or locus with restoration of the original phenotype and are called true reverse mutations. Other reversions are mutations in some other gene that change the expression of the mutant gene towards the original type, i.e. the damage in the mutant gene remains, but it seems to restore its function, resulting in the restoration of the phenotype. Such restoration (full or partial) of the phenotype despite the preservation of the original genetic damage (mutation) is called suppression, and such reverse mutations are called suppressor (extragenic). As a rule, suppression occurs as a result of mutations in genes encoding the synthesis of tRNA and ribosomes.
In general, suppression can be:
? intragenic? when a second mutation in an already affected gene changes a codon defective as a result of a direct mutation in such a way that an amino acid is inserted into the polypeptide that can restore the functional activity of this protein. Moreover, this amino acid does not correspond to the original one (before the first mutation occurred), i.e. no true reversibility observed;
? introduced? when the structure of tRNA changes, as a result of which the mutant tRNA includes in the synthesized polypeptide another amino acid instead of that encoded by a defective triplet (resulting from a direct mutation).
Compensation for the effect of mutagens due to phenotypic suppression is not excluded. It can be expected when the cell is exposed to a factor that increases the likelihood of errors in reading mRNA during translation (for example, some antibiotics). Such errors can lead to the substitution of the wrong amino acid, which, however, restores the protein function impaired as a result of direct mutation.
Mutations, in addition to their qualitative properties, are also characterized by the method of their occurrence. Spontaneous(random) - mutations that occur when normal conditions life. They are the result natural processes, occurring in cells, arise under the conditions of the natural radioactive background of the Earth in the form of cosmic radiation, radioactive elements on the surface of the Earth, radionuclides incorporated into the cells of organisms that cause these mutations or as a result of DNA replication errors. Spontaneous mutations occur in humans in somatic and generative tissues. The method for determining spontaneous mutations is based on the fact that children develop a dominant trait, although their parents do not have it. A Danish study showed that approximately one in 24,000 gametes carries a dominant mutation. The frequency of spontaneous mutation in each species is genetically determined and maintained at a certain level.
Induced mutagenesis is the artificial production of mutations using mutagens of various natures. There are physical, chemical and biological mutagenic factors. Most of these factors either directly react with nitrogenous bases in DNA molecules or are included in nucleotide sequences. The frequency of induced mutations is determined by comparing cells or populations of organisms treated and untreated with the mutagen. If the frequency of a mutation in a population increases 100 times as a result of treatment with a mutagen, then it is believed that only one mutant in the population will be spontaneous, the rest will be induced. Research on the creation of methods for the targeted effect of various mutagens on specific genes is of practical importance for the selection of plants, animals and microorganisms.
Based on the type of cells in which mutations occur, generative and somatic mutations are distinguished (see Fig. 4).
Generative mutations occur in the cells of the reproductive primordium and in the germ cells. If a mutation (generative) occurs in genital cells, then several gametes can receive the mutant gene at once, which will increase the potential ability of several individuals (individuals) to inherit this mutation in the offspring. If a mutation occurs in a gamete, then probably only one individual (individual) in the offspring will receive this gene. The frequency of mutations in germ cells is influenced by the age of the organism.
Rice. 4.
Somatic mutations occur in the somatic cells of organisms. In animals and humans, mutational changes will persist only in these cells. But in plants, due to their ability to reproduce vegetatively, the mutation can spread beyond the somatic tissues. For example, the famous winter apple variety “Delicious” originates from a mutation in a somatic cell, which, as a result of division, led to the formation of a branch that had the characteristics of a mutant type. This was followed by vegetative propagation, which made it possible to obtain plants with the properties of this variety.
The classification of mutations depending on their phenotypic effect was first proposed in 1932 by G. Möller. According to the classification, the following were identified:
Amorphous mutations. This is a condition in which the trait controlled by the pathological allele is not expressed because the pathological allele is inactive compared to the normal allele. Such mutations include the albinism gene and about 3,000 autosomal recessive diseases;
Antimorphic mutations. In this case, the value of the trait controlled by the pathological allele is opposite to the value of the trait controlled by the normal allele. Such mutations include genes of about 5-6 thousand autosomal dominant diseases;
Hypermorphic mutations. In the case of such a mutation, the trait controlled by the pathological allele is expressed stronger sign, controlled by the normal allele. Example? heterozygous carriers of genes for diseases of genome instability. Their number is about 3% of the world's population, and the number of diseases themselves reaches 100 nosologies. Among these diseases: Fanconi anemia, ataxia telangiectasia, xeroderma pigmentosum, Bloom's syndrome, progeroid syndromes, many forms of cancer, etc. Moreover, the frequency of cancer in heterozygous carriers of the genes for these diseases is 3-5 times higher than normal, and in patients themselves ( homozygotes for these genes), the incidence of cancer is tens of times higher than normal.
Hypomorphic mutations. This is a condition in which the expression of a trait controlled by a pathological allele is weakened compared to the trait controlled by a normal allele. Such mutations include mutations in pigment synthesis genes (1q31; 6p21.2; 7p15-q13; 8q12.1; 17p13.3; 17q25; 19q13; Xp21.2; Xp21.3; Xp22), as well as more than 3000 forms of autosomal recessive diseases.
Neomorphic mutations. Such a mutation is said to occur when the trait controlled by the pathological allele is of a different (new) quality compared to the trait controlled by the normal allele. Example: synthesis of new immunoglobulins in response to the penetration of foreign antigens into the body.
Speaking about the enduring significance of G. Möller’s classification, it should be noted that 60 years after its publication, the phenotypic effects of point mutations were divided into different classes depending on the effect they have on the structure of the protein product of the gene and/or its level of expression.
Mutations are changes in a cell's DNA. Occur under the influence of ultraviolet radiation, radiation (X-rays), etc. Passed on by inheritance, serve as material for natural selection.
Gene mutations- change in the structure of one gene. This is a change in the nucleotide sequence: deletion, insertion, substitution, etc. For example, replacing A with T. The reasons are violations during DNA doubling (replication). Examples: sickle cell anemia, phenylketonuria.
Chromosomal mutations- change in the structure of chromosomes: loss of a section, doubling of a section, rotation of a section by 180 degrees, transfer of a section to another (non-homologous) chromosome, etc. The reasons are violations during crossing over. Example: Cry Cat Syndrome.
Genomic mutations- change in the number of chromosomes. The causes are disturbances in the divergence of chromosomes.
- Polyploidy- multiple changes (several times, for example, 12 → 24). It does not occur in animals; in plants it leads to an increase in size.
- Aneuploidy- changes on one or two chromosomes. For example, one extra twenty-first chromosome leads to Down syndrome (and total chromosomes - 47).
Cytoplasmic mutations- changes in the DNA of mitochondria and plastids. They are transmitted only through the female line, because mitochondria and plastids from sperm do not enter the zygote. An example in plants is variegation.
Somatic- mutations in somatic cells (cells of the body; there can be four of the above types). During sexual reproduction they are not inherited. Transmitted during vegetative propagation in plants, budding and fragmentation in coelenterates (hydra).
The concepts below, except two, are used to describe the consequences of a violation of the arrangement of nucleotides in the DNA region that controls protein synthesis. Identify these two concepts that “fall out” from the general list, and write down the numbers under which they are indicated.
1) violation of the primary structure of the polypeptide
2) chromosome divergence
3) change in protein functions
4) gene mutation
5) crossing over
Answer
Choose one, the most correct option. Polyploid organisms arise from
1) genomic mutations
3) gene mutations
4) combinative variability
Answer
Establish a correspondence between the characteristic of variability and its type: 1) cytoplasmic, 2) combinative
A) occurs during independent chromosome segregation in meiosis
B) occurs as a result of mutations in mitochondrial DNA
B) occurs as a result of chromosome crossing
D) manifests itself as a result of mutations in plastid DNA
D) occurs when gametes meet by chance
Answer
Choose one, the most correct option. Down syndrome is the result of a mutation
1) genomic
2) cytoplasmic
3) chromosomal
4) recessive
Answer
1. Establish a correspondence between the characteristics of the mutation and its type: 1) genetic, 2) chromosomal, 3) genomic
A) change in the sequence of nucleotides in a DNA molecule
B) change in chromosome structure
B) change in the number of chromosomes in the nucleus
D) polyploidy
D) change in the sequence of gene location
Answer
2. Establish a correspondence between the characteristics and types of mutations: 1) gene, 2) genomic, 3) chromosomal. Write numbers 1-3 in the order corresponding to the letters.
A) deletion of a chromosome section
B) change in the sequence of nucleotides in a DNA molecule
C) a multiple increase in the haploid set of chromosomes
D) aneuploidy
D) change in the sequence of genes in a chromosome
E) loss of one nucleotide
Answer
Choose three options. What is a genomic mutation characterized by?
1) change in the nucleotide sequence of DNA
2) loss of one chromosome in the diploid set
3) a multiple increase in the number of chromosomes
4) changes in the structure of synthesized proteins
5) doubling a chromosome section
6) change in the number of chromosomes in the karyotype
Answer
1. Below is a list of characteristics of variability. All but two of them are used to describe the characteristics of genomic variation. Find two characteristics that “fall out” from the general series and write down the numbers under which they are indicated.
1) limited by the reaction norm of the trait
2) the number of chromosomes is increased and is a multiple of the haploid
3) an additional X chromosome appears
4) has a group character
5) loss of the Y chromosome is observed
Answer
2. All of the characteristics below, except two, are used to describe genomic mutations. Identify two characteristics that “fall out” from the general list and write down the numbers under which they are indicated.
1) violation of the divergence of homologous chromosomes during cell division
2) destruction of the fission spindle
3) conjugation of homologous chromosomes
4) change in the number of chromosomes
5) increase in the number of nucleotides in genes
Answer
3. All of the characteristics below, except two, are used to describe genomic mutations. Identify two characteristics that “fall out” from the general list and write down the numbers under which they are indicated.
1) change in the nucleotide sequence in a DNA molecule
2) multiple increase in chromosome set
3) reduction in the number of chromosomes
4) doubling of a chromosome section
5) nondisjunction of homologous chromosomes
Answer
4. Below is a list of characteristics of variability. All but three of them are used to describe the characteristics of genomic mutations. Find three characteristics that “fall out” from the general series and write down the numbers under which they are indicated.
1) arise as a result of redistribution of genetic material between chromosomes
2) associated with chromosome nondisjunction during meiosis
3) arise due to the loss of part of a chromosome
4) lead to the appearance of polysomy and monosomy
5) associated with the exchange of sections between non-homologous chromosomes
6) usually have a harmful effect and lead to the death of the organism
Answer
Choose one, the most correct option. Recessive gene mutations change
1) sequence of stages of individual development
2) composition of triplets in a DNA section
3) set of chromosomes in somatic cells
4) structure of autosomes
Answer
Choose one, the most correct option. Cytoplasmic variability is due to the fact that
1) meiotic division is disrupted
2) Mitochondrial DNA can mutate
3) new alleles appear in autosomes
4) gametes are formed that are incapable of fertilization
Answer
1. Below is a list of characteristics of variability. All but two of them are used to describe the characteristics of chromosomal variation. Find two characteristics that “fall out” from the general series and write down the numbers under which they are indicated.
1) loss of a chromosome section
2) rotation of a chromosome section by 180 degrees
3) reduction in the number of chromosomes in the karyotype
4) the appearance of an additional X chromosome
5) transfer of a chromosome section to a non-homologous chromosome
Answer
2. All the signs below, except two, are used to describe a chromosomal mutation. Identify two terms that “drop out” from the general list and write down the numbers under which they are indicated.
1) the number of chromosomes increased by 1-2
2) one nucleotide in DNA is replaced by another
3) a section of one chromosome is transferred to another
4) there was a loss of a part of the chromosome
5) a section of the chromosome is turned 180°
Answer
3. All but two of the characteristics below are used to describe chromosomal variation. Find two characteristics that “fall out” from the general series and write down the numbers under which they are indicated.
1) multiplication of a chromosome section several times
2) the appearance of an additional autosome
3) change in nucleotide sequence
4) loss of the terminal portion of the chromosome
5) rotation of the gene in the chromosome by 180 degrees
Answer
WE FORM
1) doubling of the same chromosome section
2) reduction in the number of chromosomes in germ cells
3) increase in the number of chromosomes in somatic cells
Choose one, the most correct option. What type of mutations are changes in the DNA structure in mitochondria?
1) genomic
2) chromosomal
3) cytoplasmic
4) combinative
Answer
Choose one, the most correct option. The variegation of night beauty and snapdragon is determined by variability
1) combinative
2) chromosomal
3) cytoplasmic
4) genetic
Answer
1. Below is a list of characteristics of variability. All but two of them are used to describe the characteristics of gene variation. Find two characteristics that “fall out” from the general series and write down the numbers under which they are indicated.
1) due to the combination of gametes during fertilization
2) caused by a change in the nucleotide sequence in the triplet
3) is formed during the recombination of genes during crossing over
4) characterized by changes within the gene
5) formed when the nucleotide sequence changes
Answer
2. All but two of the characteristics below are causes of gene mutation. Identify these two concepts that “fall out” from the general list, and write down the numbers under which they are indicated.
1) conjugation of homologous chromosomes and gene exchange between them
2) replacing one nucleotide in DNA with another
3) change in the sequence of nucleotide connections
4) the appearance of an extra chromosome in the genotype
5) loss of one triplet in the DNA region encoding the primary structure of the protein
Answer
3. All of the characteristics below, except two, are used to describe gene mutations. Identify two characteristics that “fall out” from the general list and write down the numbers under which they are indicated.
1) replacement of a pair of nucleotides
2) the occurrence of a stop codon within the gene
3) doubling the number of individual nucleotides in DNA
4) increase in the number of chromosomes
5) loss of a chromosome section
Answer
4. All of the characteristics below, except two, are used to describe gene mutations. Identify two characteristics that “fall out” from the general list and write down the numbers under which they are indicated.
1) adding one triplet to DNA
2) increase in the number of autosomes
3) change in the sequence of nucleotides in DNA
4) loss of individual nucleotides in DNA
5) multiple increase in the number of chromosomes
Answer
5. All of the characteristics below, except two, are typical for gene mutations. Identify two characteristics that “fall out” from the general list and write down the numbers under which they are indicated.
1) the emergence of polyploid forms
2) random doubling of nucleotides in a gene
3) loss of one triplet during replication
4) formation of new alleles of one gene
5) violation of the divergence of homologous chromosomes in meiosis
Answer
FORMING 6:
1) a section of one chromosome is transferred to another
2) occurs during DNA replication
3) a part of a chromosome is lost
Choose one, the most correct option. Polyploid wheat varieties are the result of variability
1) chromosomal
2) modification
3) genetic
4) genomic
Answer
Choose one, the most correct option. It is possible for breeders to obtain polyploid wheat varieties due to mutation
1) cytoplasmic
2) genetic
3) chromosomal
4) genomic
Answer
Establish a correspondence between characteristics and mutations: 1) genomic, 2) chromosomal. Write numbers 1 and 2 in the correct order.
A) multiple increase in the number of chromosomes
B) rotate a section of a chromosome by 180 degrees
B) exchange of sections of non-homologous chromosomes
D) loss of the central part of the chromosome
D) doubling of a chromosome section
E) multiple change in the number of chromosomes
Answer
Choose one, the most correct option. The appearance of different alleles of the same gene occurs as a result
1) indirect division cells
2) modification variability
3) mutation process
4) combinative variability
Answer
All but two of the terms listed below are used to classify mutations by changes in genetic material. Identify two terms that “drop out” from the general list and write down the numbers under which they are indicated.
1) genomic
2) generative
3) chromosomal
4) spontaneous
5) genetic
Answer
Establish a correspondence between the types of mutations and their characteristics and examples: 1) genomic, 2) chromosomal. Write numbers 1 and 2 in the order corresponding to the letters.
A) loss or appearance of extra chromosomes as a result of meiotic disorder
B) lead to disruption of gene functioning
C) an example is polyploidy in protozoa and plants
D) duplication or loss of a chromosome section
D) a striking example is Down syndrome
Answer
Establish a correspondence between the categories of hereditary diseases and their examples: 1) genetic, 2) chromosomal. Write numbers 1 and 2 in the order corresponding to the letters.
A) hemophilia
B) albinism
B) color blindness
D) “cry of the cat” syndrome
D) phenylketonuria
Answer
Find three errors in the given text and indicate the numbers of sentences with errors.(1) Mutations are randomly occurring persistent changes genotype. (2) Gene mutations are the result of “errors” that occur during the duplication of DNA molecules. (3) Genomic mutations are those that lead to changes in the structure of chromosomes. (4) Many cultivated plants are polyploids. (5) Polyploid cells contain one to three extra chromosomes. (6) Polyploid plants are characterized by more vigorous growth and larger sizes. (7) Polyploidy is widely used in both plant and animal breeding.
Answer
Analyze the table “Types of variability”. For each cell indicated by a letter, select the corresponding concept or corresponding example from the list provided.
1) somatic
2) genetic
3) replacement of one nucleotide with another
4) gene duplication in a section of a chromosome
5) addition or loss of nucleotides
6) hemophilia
7) color blindness
8) trisomy in the chromosome set
Answer
© D.V. Pozdnyakov, 2009-2019
Variability- the ability of living organisms to acquire new characteristics and properties. Thanks to variability, organisms can adapt to changing environmental conditions.
There are two main forms of variability: hereditary and non-hereditary.
Hereditary, or genotypic, variability- changes in the characteristics of the organism due to changes in the genotype. It, in turn, is divided into combinative and mutational. Combinative variability arises due to the recombination of hereditary material (genes and chromosomes) during gametogenesis and sexual reproduction. Mutational variability arises as a result of changes in the structure of hereditary material.
Non-hereditary, or phenotypic, or modification, variability- changes in the characteristics of the organism that are not due to changes in the genotype.
Mutations
Mutations- these are persistent, sudden changes in the structure of the hereditary material at various levels of its organization, leading to changes in certain characteristics of the organism.
The term “mutation” was introduced into science by De Vries. Created by him mutation theory, the main provisions of which have not lost their significance to this day.
- Mutations arise suddenly, spasmodically, without any transitions.
- Mutations are hereditary, i.e. are persistently passed on from generation to generation.
- Mutations do not form continuous rows, are not grouped around the average type (as with modification variability), they are qualitative changes.
- Mutations are undirected - any locus can mutate, causing changes both minor and vital important signs in any direction.
- The same mutations can occur repeatedly.
- Mutations are individual, that is, they occur in individual individuals.
The process of mutation occurrence is called mutagenesis, and environmental factors causing mutations are mutagens.
Based on the type of cells in which the mutations occurred, they are distinguished: generative and somatic mutations.
Generative mutations arise in germ cells, do not affect the characteristics of a given organism, and appear only in the next generation.
Somatic mutations arise in somatic cells, manifest themselves in a given organism and are not transmitted to offspring during sexual reproduction. Somatic mutations can be preserved only through asexual reproduction (primarily vegetative).
According to their adaptive value, they are divided into: beneficial, harmful (lethal, semi-lethal) and neutral mutations. Useful- increase vitality, lethal- cause death semi-lethal- reduce vitality, neutral- do not affect the viability of individuals. It should be noted that the same mutation can be beneficial in some conditions and harmful in others.
According to the nature of their manifestation, mutations can be dominant And recessive. If a dominant mutation is harmful, then it can cause the death of its owner in the early stages of ontogenesis. Recessive mutations do not appear in heterozygotes, therefore they remain in the population for a long time in a “hidden” state and form a reserve of hereditary variability. When environmental conditions change, carriers of such mutations may gain an advantage in the struggle for existence.
Depending on whether the mutagen that caused this mutation has been identified or not, they distinguish induced And spontaneous mutations. Spontaneous mutations usually occur naturally induced - caused artificially.
Depending on the level of hereditary material at which the mutation occurred, gene, chromosomal and genomic mutations are distinguished.
Gene mutations
Gene mutations- changes in gene structure. Since a gene is a section of a DNA molecule, a gene mutation represents changes in the nucleotide composition of this section. Gene mutations can occur as a result of: 1) replacement of one or more nucleotides with others; 2) nucleotide insertions; 3) loss of nucleotides; 4) doubling of nucleotides; 5) changes in the order of alternation of nucleotides. These mutations lead to changes in the amino acid composition of the polypeptide chain and, consequently, to changes in the functional activity of the protein molecule. Gene mutations result in multiple alleles of the same gene.
Diseases caused by gene mutations are called genetic diseases (phenylketonuria, sickle cell anemia, hemophilia, etc.). The inheritance of gene diseases obeys Mendel's laws.
Chromosomal mutations
These are changes in the structure of chromosomes. Rearrangements can occur both within one chromosome - intrachromosomal mutations (deletion, inversion, duplication, insertion), and between chromosomes - interchromosomal mutations (translocation).
Deletion— loss of a chromosome section (2); inversion— rotation of a chromosome section by 180° (4, 5); duplication- doubling of the same chromosome section (3); insertion— rearrangement of the area (6).
Chromosomal mutations: 1 - parachromosomes; 2 - deletion; 3 - duplication; 4, 5 — inversion; 6 - insertion.
Translocation- transfer of a section of one chromosome or an entire chromosome to another chromosome.
Diseases caused by chromosomal mutations are classified as chromosomal diseases. Such diseases include the “cry of the cat” syndrome (46, 5p -), translocation variant of Down syndrome (46, 21 t21 21), etc.
Genomic mutation called a change in the number of chromosomes. Genomic mutations occur as a result of disruption of the normal course of mitosis or meiosis.
Haploidy- reduction in the number of complete haploid sets of chromosomes.
Polyploidy- increase in the number of complete haploid sets of chromosomes: triploids (3 n), tetraploids (4 n) etc.
Heteroploidy (aneuploidy) - a multiple increase or decrease in the number of chromosomes. Most often, there is a decrease or increase in the number of chromosomes by one (less often two or more).
The most likely cause of heteroploidy is the nondisjunction of any pair of homologous chromosomes during meiosis in one of the parents. In this case, one of the resulting gametes contains one less chromosome, and the other contains one more. The fusion of such gametes with a normal haploid gamete during fertilization leads to the formation of a zygote with a smaller or a large number chromosomes compared to the diploid set characteristic of this species: nullosomia (2n - 2), monosomy (2n - 1), trisomy (2n + 1), tetrasomy (2n+ 2) etc.
On genetic circuits, given below, it is shown that the birth of a child with Klinefelter syndrome or Turner-Shereshevsky syndrome can be explained by the nondisjunction of sex chromosomes during anaphase 1 of meiosis in the mother or father.
1) Nondisjunction of sex chromosomes during meiosis in the mother
| R | ♀46,XX | × | ♂46,XY | ||
| Types of gametes | 24, XX 24, 0 | 23, X 23, Y | |||
| F | 47, XXX trisomy on the X chromosome |
47, XXY syndrome Klinefelter |
45, X0 Turner syndrome- Shereshevsky |
45,Y0 death zygotes |
|
2) Nondisjunction of sex chromosomes during meiosis in the father
| R | ♀46,XX | × | ♂46,XY |
| Types of gametes | 23, X | 24, XY 22, 0 | |
| F | 47, XXY syndrome Klinefelter |
45, X0 Turner syndrome- Shereshevsky |
Diseases caused by genomic mutations also fall into the chromosomal category. Their inheritance does not obey Mendel's laws. In addition to the above-mentioned Klinefelter or Turner-Shereshevsky syndromes, such diseases include Down syndrome (47, +21), Edwards syndrome (+18), Patau syndrome (47, +15).
Polyploidy characteristic of plants. The production of polyploids is widely used in plant breeding.
The law of homological series of hereditary variability N.I. Vavilova
“Species and genera that are genetically close are characterized by similar series of hereditary variability with such regularity that, knowing the series of forms within one species, one can predict the presence of parallel forms in other species and genera. The closer they are genetically located in common system genera and species, the more complete the similarity in the ranks of their variability. Whole families of plants are generally characterized by a certain cycle of variation passing through all the genera and species that make up the family.”
This law can be illustrated by the example of the Poa family, which includes wheat, rye, barley, oats, millet, etc. Thus, the black color of the caryopsis was found in rye, wheat, barley, corn and other plants, and the elongated shape of the caryopsis was found in all studied species of the family. The law of homological series in hereditary variability allowed N.I. himself. Vavilov to find a number of forms of rye, previously unknown, based on the presence of these characteristics in wheat. These include: awned and awnless ears, grains of red, white, black and purple color, mealy and glassy grains, etc.
| Hereditary variation of traits * | Rye | Wheat | Barley | Oats | Millet | Sorghum | Corn | Rice | Wheatgrass | ||
| Corn | Coloring | Black | + | + | + | — | — | + | + | + | + |
| Purple | + | + | + | — | — | + | + | + | — | ||
| Form | Round | + | + | + | + | + | + | + | + | + | |
| Extended | + | + | + | + | + | + | + | + | + | ||
| Biol. signs | Lifestyle | Winter crops | + | + | + | + | + | ||||
| Spring | + | + | + | + | + | + | + | + | |||
* Note. The “+” sign means the presence of hereditary forms that have the specified trait.
Open N.I. Vavilov’s law is valid not only for plants, but also for animals. Thus, albinism occurs not only in different groups mammals, but also birds and other animals. Short-fingeredness is observed in humans, cattle, sheep, dogs, birds, the absence of feathers in birds, scales in fish, wool in mammals, etc.
The law of homological series of hereditary variability has great importance for selection, since it allows one to predict the presence of forms not found in a given species, but characteristic of closely related species. Moreover, the desired form can be found in the wild or obtained through artificial mutagenesis.
Artificial mutations
Spontaneous mutagenesis constantly occurs in nature, but spontaneous mutations are quite a rare event For example, in Drosophila, the white eye mutation is formed with a frequency of 1:100,000 gametes.
Factors whose impact on the body leads to the appearance of mutations are called mutagens. Mutagens are usually divided into three groups. Physical and chemical mutagens are used to artificially produce mutations.
Induced mutagenesis is of great importance because it makes it possible to create valuable starting material for breeding, and also reveals ways to create means of protecting humans from the action of mutagenic factors.
Modification variability
Modification variability- these are changes in the characteristics of organisms that are not caused by changes in the genotype and arise under the influence of factors external environment. The habitat plays a big role in the formation of the characteristics of organisms. Each organism develops and lives in a certain environment, experiencing the action of its factors that can change the morphological and physiological properties of organisms, i.e. their phenotype.
An example of the variability of traits under the influence of environmental factors is different shape leaves of arrowhead: leaves immersed in water have a ribbon-like shape, leaves floating on the surface of the water are rounded, and those in the air are arrow-shaped. Under the influence of ultraviolet rays, people (if they are not albinos) develop a tan as a result of the accumulation of melanin in the skin, and the intensity of the skin color varies from person to person.
Modification variability is characterized by the following main properties: 1) non-heritability; 2) the group nature of the changes (individuals of the same species placed in the same conditions acquire similar characteristics); 3) correspondence of changes to the influence of environmental factors; 4) dependence of the limits of variability on the genotype.
Despite the fact that signs may change under the influence of environmental conditions, this variability is not unlimited. This is explained by the fact that the genotype determines specific boundaries within which changes in a trait can occur. The degree of variation of a trait, or the limits of modification variability, is called reaction norm. The reaction norm is expressed in the totality of phenotypes of organisms formed on the basis of a certain genotype under the influence various factors environment. As a rule, quantitative traits (plant height, yield, leaf size, milk yield of cows, egg production of chickens) have a wider reaction rate, that is, they can vary widely than qualitative traits (coat color, milk fat content, flower structure, blood type) . Knowledge of reaction norms is of great importance for agricultural practice.
Modification variability of many traits of plants, animals and humans is subject to general patterns. These patterns are identified based on the analysis of the manifestation of the trait in a group of individuals ( n). The degree of expression of the studied trait in members sample population different. Each specific value of the characteristic being studied is called option and denoted by the letter v. The frequency of occurrence of individual variants is indicated by the letter p. When studying the variability of a trait in a sample population, a variation series is compiled in which individuals are arranged in ascending order of the indicator of the trait being studied.
For example, if you take 100 ears of wheat ( n= 100), count the number of spikelets in an ear ( v) and the number of ears with a given number of spikelets, then the variation series will look as follows.
| Variant ( v) | 14 | 15 | 16 | 17 | 18 | 19 | 20 |
| Frequency of occurrence ( p) | 2 | 7 | 22 | 32 | 24 | 8 | 5 |
Based on the variation series, it is constructed variation curve— graphical display of the frequency of occurrence of each option.
The average value of a characteristic is more common, and variations significantly different from it are less common. It is called « normal distribution» . The curve on the graph is usually symmetrical.
The average value of the characteristic is calculated using the formula:
Where M— average value of the characteristic; ∑( v
