Analysis of task 27 in the exam in biology.

| Biology Real tasks 27 1. What chromosome set is characteristic of fern leaf cells and spores? From what initial cells and as a result of what division are they formed? 1. Chromosome set of cells of fern leaves 2n (adult plant – sporophyte). 2. The chromosome set of fern spores1n is formed from the cells of an adult plant (sporophyte) by meiosis. 3. Spores are formed from sporophyte cells by meiosis. Leaf cells are formed from sporophyte cells by mitosis, sporophyte develops from zygote by mitosis. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 2. What chromosome set do the scale cells of female cones and megaspores of spruce have? From what initial cells and as a result of what division are they formed? 1. Chromosome set of cells in the scales of female spruce cones2n (adult sporophyte plant). 2. The chromosome set of the spel1n megaspore is formed from the cells of an adult plant (sporophyte) by meiosis. 3. The scale cells of female cones are formed from sporophyte cells by mitosis, the sporophyte develops from the seed embryo by mitosis. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 3. Drosophila somatic cells contain 8 chromosomes. Determine the number of chromosomes and DNA molecules contained in the nuclei during gametogenesis in interphase and metaphase of meiosis I. 1. Somatic cells of Drosophila have a set of chromosomes 2n, a set of DNA 2c; 8 chromosomes8 DNA. 2. Before meiosis (at the end of interphase), DNA replication occurred, the set of chromosomes remained unchanged, but each chromosome now consists of two chromatids. Therefore, the chromosome set is 2n, the DNA set is 4c; 8 chromosomes 16 DNA. 3. In metaphase I of meiosis, the set of chromosomes and DNA remains unchanged (2n4c). Pairs of homologous chromosomes (bivalents) are lined up along the equator of the cell, and spindle threads are attached to the centromeres of the chromosomes. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 4. What is the chromosome set of horsetail spores and gametes? From what initial cells and as a result of what division are they formed? 1. Chromosome set of horsetail spores1n. 2. Chromosome set of horsetail gametes1n. 3. Spores are formed from sporophyte cells (2n) by meiosis. Gametes (sex cells) are formed from gametophyte cells (1n) by mitosis. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 5. Determine the chromosome set of the macrospore from which the eight-nucleated embryo sac and the egg cell are formed. Determine from which cells and by what division the macrospore and egg are formed. 1. Chromosome set of macrospore1n. 2. Chromosome set of egg1n. 3. Macrospores are formed from sporophyte cells (2n) by meiosis. The egg (sex cell, gamete) is formed from gametophyte cells (1n) by mitosis. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 6. The chromosome set of wheat somatic cells is 28. Determine the chromosome set and the number of DNA molecules in the ovule cell at the end of meiosis I and meiosis II. Explain the results in each case. 1. Somatic cells of wheat have a set of chromosomes 2n, a set of DNA 2c; 28 chromosomes 28 DNA. 2. At the end of meiosis I (telophase of meiosis I), the set of chromosomes is 1n, the set of DNA is 2c; 14 chromosomes 28 DNA. The first division of meiosis is reduction, in each resulting cell there is a haploid set of chromosomes (n), each chromosome consists of two chromatids (2c); There are no homologous chromosomes in isolated nuclei, since during anaphase of meiosis1 homologous chromosomes diverge to the poles of the cell. 3. At the end of meiosis II (telophase of meiosis II), the set of chromosomes is 1n, the set of DNA is 1c; 14 chromosomes 14 DNA. Each resulting cell has a haploid set of chromosomes (n), each chromosome consists of one chromatid (1c), since in anaphase II of meiosis sister chromatids (chromosomes) diverge to the poles. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 7. A somatic cell of an animal is characterized by a diploid set of chromosomes. Determine the chromosome set (n) and the number of DNA molecules (c) in the cell nucleus during gametogenesis in metaphase I of meiosis and anaphase II of meiosis. Explain the results in each case. 1. In metaphase I of meiosis, the set of chromosomes is 2n, the number of DNA is 4c 2. In anaphase II of meiosis, the set of chromosomes is 2n, the number of DNA is 2c 3. Before meiosis (at the end of interphase), DNA replication occurred, therefore, in metaphase I of meiosis, the number of DNA is doubled. 4. After the first reduction division of meiosis in anaphase II of meiosis, sister chromatids (chromosomes) diverge to the poles, therefore the number of chromosomes is equal to the number of DNA. (Unified State Exam Expert Key) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 8. It is known that all types of RNA are synthesized on a DNA matrix. The fragment of the DNA molecule on which the tRNA section is synthesized has the following nucleotide sequence TTGGAAAAACGGATCT. Determine the nucleotide sequence of the tRNA region that is synthesized on this fragment. Which mRNA codon will correspond to the central anticodon of this tRNA? Which amino acid will be transported by this tRNA? Explain your answer. To solve the task, use the genetic code table. Principle of complementarity: AT(U), GC. 1. The nucleotide sequence of the region (central loop) of tRNA is AATCCUUUUUUGCC UGA; 2. The nucleotide sequence of the anticodon (central triplet) of tRNA is UUU, which corresponds to the mRNA codon – AAA. 3. This tRNA will transport amino acid – lys. The amino acid is determined by the genetic code (mRNA) table. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 9. The genetic apparatus of the virus is represented by an RNA molecule, a fragment of which has the following nucleotide sequence: GUGAAAAGAUCAUGCGUGG. Determine the nucleotide sequence of a double-stranded DNA molecule, which is synthesized as a result of reverse transcription on the RNA of the virus. Establish the sequence of nucleotides in mRNA and amino acids in the protein fragment of the virus, which is encoded in the found fragment of the DNA molecule. The matrix for the synthesis of mRNA, on which the synthesis of the viral protein occurs, is the second strand of double-stranded DNA. To solve the problem, use the genetic code table. Principle of complementarity: AT(U), GC. 1. RNA of the virus: GGG AAA GAU CAU GCG UGG DNA1 chain: TsAC TTT CTA GTA CGC ACC DNA2 chain: GTG AAA GAT CAT GCG TGG 2. mRNA CAC UUU CUA GUA CGC ACC (built on the principle of complementarity along the second strand of the DNA molecule) 3 Amino acid sequence: hys-phene-leu-val-arg-tre (determined from the genetic code table (mRNA).

“Solve the Unified State Exam” provides applicants with 3 sections with tasks in cytology:

1. Protein biosynthesis
2. Cell division

The task is of a high level of difficulty, for correct execution relies 3 points. There is nothing scary about tasks. After all, everything is usually clear in them. You just need to understand the essence once, and then they will be one of the expected and favorite tasks.

In order to avoid incorrect formatting and other troubles, tasks, solutions will be laid out below, in the form in which they should be written down on a special form for the second part, a scale with points so that you can understand how each point of the solution is assessed and comments that will help you with your assignments. The first tasks of the analysis will be described in great detail, so it is better to familiarize yourself with them. Below are variations of the tasks. All of them are decided according to the same principle. Cell division tasks are based on mitosis and meiosis, which applicants have already become familiar with earlier, in the first part.

Protein biosynthesis

The tRNA anticodons arrive at the ribosomes in the following nucleotide sequence UCG, CGA, AAU, CCC. Determine the sequence of nucleotides on mRNA, the sequence of nucleotides on DNA encoding a specific protein and the sequence of amino acids in a fragment of a synthesized protein molecule using the genetic code table:

We have been given tRNA. We build an mRNA chain using the principle of complementarity.

Let me remind you what pairs RNA has: A is complementary to U, G is complementary to C.

For convenience, in the draft, we write out the tRNA chain from the condition so as not to lose any nucleotide:

UCG TsGA AAU CCC

Note: when we write tRNA, we do not put any hyphens or anything else. It’s better not to even write commas, just write separated by a space. This is due to the structure of tRNA.

We write down the resulting mRNA:

AGC-GCU-UUA-GGG

Now, according to the principle of complementarity, we build a DNA chain using mRNA

I remind you of the pairs in DNA: A is complementary to T, C is complementary to G

UCG-TsGA-AAT-CCTs

Now let's determine the sequence of the resulting amino acids in mRNA. To do this, we will use the genetic code table that is included in the assignment.

How to use the table? Let's look at our sequence.

First amino acid sequence: AHC

1. We find the first base in the first column of the table - A.
2. Find the second base among columns 2-4. Our base is G. Column 4 of the table corresponds to it.
3. We find the last, third base. For us, this is C. In the last column, we look for the letter C in the first line. Now we look for the intersection with the desired column, pointing to the second base.
4. We get the amino acid “ser”

Let's define the remaining amino acids:

GCU – “ala”

UUA – “ley”

YYY - "gli"

Final sequence: ser-ala-lay-gli

It is known that all types of RNA are synthesized on a DNA template. The fragment of the DNA molecule on which the tRNA section is synthesized has the following nucleotide sequence ATA-GCT-GAA-CHG-ACT. Determine the nucleotide sequence of the tRNA region that is synthesized on this fragment. Which mRNA codon will correspond to the anticodon of this tRNA if it transfers the amino acid GLU to the site of protein synthesis. Explain your answer. To solve the problem, use the genetic code table:

1. Using the principle of complementarity, we build a tRNA chain:

I remind you of the pairs in RNA: A is complementary to U, G is complementary to C.

1. For convenience, let's write down the DNA chain:

ATA-GCT-GAA-CGG-ACT

UAU TsGA TSUU GCC UGA

1. Let's build an mRNA to find which anticodon mRNA carries the amino acid "glu". Here it is as convenient for anyone. Someone can immediately determine from the table, someone can write the entire chain, write down the amino acids, select the right one and answer the question posed. You don’t have to rewrite the entire chain into a clean copy, but only the necessary triplet.

AUA-GCU-GAA-TsGG-ATSU

1. Let's write out the amino acids from the table:

ile-ala-glu-arg-tre

1. We find the amino acid “glu”. It corresponds to the third triplet of nucleotides in mRNA, therefore - GAA, which is complementary to the triplet CUU in tRNA.

The sequence of amino acids in a fragment of a protein molecule is as follows: FEN-GLU-MET. Using the genetic code table, determine the possible DNA triplets that encode this protein fragment.

1. Let's make a chain of mRNA. To do this, let's write out the amino acids from the condition and find the corresponding nucleotide triplets. Attention! One amino acid can be encoded by several triplets.

FEN – UUU or UUC

GLU – GAA or GAG

MET – AUG

1. Let's define DNA triplets based on the principle of complementarity

The translation process involved 30 tRNA molecules. Determine the number of amino acids that make up the protein being synthesized, as well as the number of triplets and nucleotides in the gene that encodes this protein.

T-RNA molecules with anticodons UGA, AUG, AGU, GGC, AAU participate in the biosynthesis of the polypeptide. Determine the nucleotide sequence of the section of each chain of the DNA molecule that carries information about the polypeptide being synthesized, and the number of nucleotides containing adenine (A), guanine (G), thymine (T), cytosine (C) in a double-stranded DNA molecule. Explain your answer.

Ribosomes from different cells, the entire set of amino acids and identical molecules of mRNA and tRNA were placed in a test tube, and all conditions were created for protein synthesis. Why will one type of protein be synthesized on different ribosomes in a test tube?

Cell division

The total mass of all DNA molecules in the 46 somatic chromosomes of one human somatic cell is 6x10-9 mg. Determine the mass of all DNA molecules in the sperm and in the somatic cell before division begins and after it ends. Explain your answer.

Which division of meiosis is similar to mitosis? Explain what it means. What set of chromosomes in a cell does meiosis lead to?.

1. similarities with mitosis are observed in the second division of meiosis;
2. all phases are similar, sister chromosomes (chromatids) diverge to the poles of the cell;
3. the resulting cells have a haploid set of chromosomes.

What chromosome set is characteristic of the cells of the embryo and endosperm of the seed, leaves of a flowering plant. Explain the result in each case.

1. in the cells of the seed embryo, the diploid set of chromosomes is 2n, since the embryo develops from a zygote - a fertilized egg;
2. in the endosperm cells of the seed, the triploid set of chromosomes is 3n, as it is formed by the fusion of two nuclei of the central cell of the ovule (2n) and one sperm (n);
3. The leaf cells of a flowering plant have a diploid set of chromosomes - 2n, since an adult plant develops from an embryo.

The chromosome set of somatic wheat cells is 28. Determine the chromosome set and the number of DNA molecules in one of the ovule cells before the onset of meiosis, in anaphase of meiosis 1 and in anaphase of meiosis 2. Explain what processes occur during these periods and how they affect the change in the number of DNA and chromosomes.

The cells of the ovule contain a diploid set of chromosomes - 28 (2n2c).

Before the start of meiosis in the S-period of interphase, DNA duplication occurs: 28 chromosomes, 56 DNA (2n4c).

In anaphase of meiosis 1, chromosomes consisting of two chromatids diverge to the poles of the cell. The genetic material of the cell will be (2n4c = n2c+n2c) - 28 chromosomes, 56 DNA.

Meiosis 2 involves 2 daughter cells with a haploid set of chromosomes (n2c) - 14 chromosomes, 28 DNA.

In anaphase 2 of meiosis, chromatids move toward the poles of the cell. After chromatid divergence, the number of chromosomes increases by 2 times (chromatids become independent chromosomes, but for now they are all in one cell) – (2n2с= nc+nc) – 28 chromosomes, 28 DNA

Indicate the number of chromosomes and the number of DNA molecules in the prophase of the first and second meiotic cell division. What event happens to chromosomes during prophase of the first division?

1. In the prophase of the first division, the number of chromosomes and DNA corresponds to the formula 2n4c.

2. In the prophase of the second division, the formula is p2c, since the cell is haploid.

3. In the prophase of the first division, conjugation and crossing over of homologous chromosomes occur

A somatic cell of an animal is characterized by a diploid set of chromosomes. Determine the chromosome set (n) and the number of DNA molecules (c) in the cell in prophase of meiosis I and metaphase of meiosis II. Explain the results in each case.

Diploid chromosome set 2n2c

1. Before the start of meiosis in the S-period of interphase - DNA doubling: Prophase of meiosis I - 2n4c
2. The first division is reduction. Meiosis 2 involves 2 daughter cells with a haploid set of chromosomes (n2c)
3. Metaphase of meiosis II - chromosomes line up at the equator n2

What chromosome set is characteristic of gametes and spores of the cuckoo flax moss plant? Explain from which cells and as a result of what division they are formed.

1. Gametes of the cuckoo flax moss are formed on gametophytes from a haploid cell by mitosis.
2. The set of chromosomes in gametes is haploid (single) - n.
3. Cuckoo flax moss spores are formed on a diploid sporophyte in sporangia by meiosis from diploid cells.
4. The set of chromosomes in spores is haploid (single) - n

What chromosome set is characteristic of the gametophyte and gametes of sphagnum moss? Explain from what initial cells and as a result of what division these cells are formed?

1. The gametophyte and sphagnum gametes are haploid, and the set of chromosomes and the amount of DNA in the cells correspond to the formula nc. Sphagnum gametes are formed on the haploid gametophyte by mitosis.
2. The gametophyte is formed from a spore, which is produced by meiosis from sporophyte tissues.
3. The spore divides by mitosis to form a gametophyte.

Look at the person's karyotype and answer the questions.

1. What gender is this person?

2. What abnormalities does this person’s karyotype have?

3. What events can cause such deviations?

1. Gender: male.

2. There are two X chromosomes in the karyotype ( or, violation in the sex chromosomes: two X and another Y).

3. Such deviations may occur due to chromosome nondisjunction during the first meiotic division.

Such deviations can occur due to the entry of two homologous chromosomes into one cell during the first meiotic division.

What chromosome set is characteristic of the vegetative, generative cells and sperm cells of the pollen grain of a flowering plant? Explain from what initial cells and as a result of what division these cells are formed.

1. set of chromosomes of vegetative and generative cells - n;
2. vegetative and generative pollen cells are formed by mitosis during the germination of a haploid spore;
3. chromosome set of sperm - n;
4. sperm are formed from a generative cell through mitosis

How the number of chromosomes and DNA in a male cell changes during spermatogenesis at the stages: interphase I, telophase I, anaphase II, telophase II.

1. In interphase I there are 2n4c or 46 bichromatid chromosomes and 92 DNA molecules.
2. Telophase I – n2c or 23 bichromatid chromosomes and 46 DNA molecules.
3. Anaphase II – 2n2c or 46 single-chromatid chromosomes (23 at each pole) and 46 DNA molecules.
4. Telophase II - nc, or 23 single-chromatid chromosomes and 23 DNA molecules in each gamete

In the green alga Ulothrix, the predominant generation is the gametophyte. What chromosome set do the cells of an adult organism and a sporophyte have? Explain what the sporophyte is represented by, from what initial cells and as a result of what process the adult organism and sporophyte are formed.

1. the chromosome set in the cells of an adult organism is n (haploid), sporophyte - 2n (diploid);
2. the adult organism is formed from a haploid spore by mitosis;
3. sporophyte is a zygote, formed by the fusion of gametes during fertilization

Chargaff's Rule/Energy Exchange

The gene contains 1500 nucleotides. One of the chains contains 150 nucleotides A, 200 nucleotides T, 250 nucleotides G and 150 nucleotides C. How many nucleotides of each type will there be in the DNA chain encoding a protein? How many amino acids will be encoded by this DNA fragment?

A little historical information about who Chargaff is and what he did:

In one DNA molecule, nucleotides with thymine (T) account for 24% of the total number of nucleotides. Determine the number (in%) of nucleotides with guanine (G), adenine (A), cytosine (C) in the DNA molecule and explain the results.

The DNA strand is given: CTAATGTAATCA. Define:

A) The primary structure of the encoded protein.

B) Percentage various types nucleotides in this gene (in two chains).

B) The length of this gene.

D) The length of the protein.

Note from the site's creators.

Length of 1 nucleotide - 0.34 nm

The length of one amino acid is 0.3 nm

The length of the nucleotide and amino acid are tabular data, you need to know them (not included in the conditions)

During glycolysis, 112 molecules of pyruvic acid (PVA) were formed. How many glucose molecules are broken down and how many ATP molecules are formed during the complete oxidation of glucose in eukaryotic cells? Explain your answer.

1. In the process of glycolysis, when 1 molecule of glucose is broken down, 2 molecules of pyruvic acid are formed and energy is released, which is enough for the synthesis of 2 ATP molecules.
2. If 112 molecules of pyruvic acid were formed, then, therefore, 112: 2 = 56 glucose molecules were split.
3. With complete oxidation, 38 ATP molecules are formed per glucose molecule.

Therefore, with the complete oxidation of 56 glucose molecules, 38 x 56 = 2128 ATP molecules are formed

During the oxygen stage of catabolism, 972 ATP molecules were formed. Determine how many glucose molecules were broken down and how many ATP molecules were formed as a result of glycolysis and complete oxidation? Explain your answer.

1. In the process of energy metabolism, during the oxygen stage, 36 ATP molecules are formed from one glucose molecule, therefore, glycolysis, and then 972 were subjected to complete oxidation: 36 = 27 glucose molecules.
2. During glycolysis, one molecule of glucose is broken down into 2 molecules of PVK with the formation of 2 molecules of ATP. Therefore, the number of ATP molecules formed during glycolysis is 27 × 2 = 54.
3. With the complete oxidation of one glucose molecule, 38 ATP molecules are formed, therefore, with the complete oxidation of 27 glucose molecules, 38 × 27 = 1026 ATP molecules are formed.

Examples of Unified State Exam tasks on line 27 (part 1)

1. Drosophila somatic cells contain 8 chromosomes. How will the number of chromosomes change and

DNA molecules in the nucleus during gametogenesis before the start of division and at the end of the telophase of meiosis 1.

Explain the results in each case.

2. A somatic cell of an animal is characterized by a diploid set of chromosomes. Define

chromosome set (n) and number of DNA molecules (c) at the end of telophase of meiosis 1 and anaphase of meiosis

II. Explain the results in each case.

Independent work: Repeat the topic “Meiosis”, know the biological significance of meiosis.

3. What chromosome set is characteristic of gametes and spores of the cuckoo flax moss plant?

Explain from which cells and as a result of what division they are formed.

4. Reveal the mechanisms that ensure the constancy of the number and shape of chromosomes in all

cells of organisms from generation to generation.

Independent work: Review the material about mitosis and meiosis.

5. The total mass of all DNA molecules in 46 chromosomes of one human somatic cell

is about 6 x 10

mg. Determine the mass of all DNA molecules in the sperm

and in a somatic cell before the start of mitotic division and after its completion. Answer

explain.

Independent work: Review material about the structure of DNA

6. What is the set of chromosomes (n) and the number of DNA molecules (c) in a diploid cell in prophase and

anaphase of meiosis? Explain the results in each case.

Independent work: Repeat the topic “Meiosis”, know the biological significance of meiosis.

7. The somatic cell of an animal is characterized by a diploid set of chromosomes- 2 n. Which

set of chromosomes and DNA molecules in cells at the end of the synthetic period of interphase and in

end of telophase meiosis 1?

Independent work: Repeat the topic “Meiosis”, know the definitions: diploid,

haploid sets of chromosomes, phases of mitosis and meiosis.

8. Determine the chromosome set in the cells of an adult plant and in the spores of a moss plant

cuckoo flax? As a result of what type of division and from which cells are these chromosome sets

are formed?

Independent work: Repeat the development cycle of cuckoo flax moss.

9. What chromosome set is characteristic of the cells of the fern prothallus? Explain from

what cells and as a result of what division are they formed?

Independent work: Consider the development cycle of a fern.

10. What chromosome set is characteristic of the embryonic and endosperm cells of the seed and leaves?

Description of the presentation by individual slides:

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Municipal budgetary educational institution "Karpovskaya secondary school" of the Urensky municipal district of the Nizhny Novgorod region "Analysis of task 27 of part C of the Unified State Exam in biology" Prepared by: teacher of biology and chemistry MBOU "Karpovskaya secondary school" Chirkova Olga Aleksandrovna 2017

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Task 27. Cytology task. Protein biosynthesis Task 1. A fragment of an i-RNA chain has the nucleotide sequence: CUTSACCTGCAGUA. Determine the sequence of nucleotides in DNA, the anticodons of tRNA, and the sequence of amino acids in a fragment of a protein molecule using the genetic code table.

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Task 27. Cytology task. Protein biosynthesis Solution algorithm 1. Read the task carefully. Determine what needs to be done. 2. Make a note according to the plan: DNA i-RNA C U C A C C G C A G U A t-RNA Amino acids 3. Write down the sequence of the DNA chain. To do this, use the principle of complementarity (cytosine - guanine, uracil - adenine (there is no nitrogenous base uracil in DNA). DNA G A G T G G C G T C A T i-RNA C U C A C C G C A G U A t-RNA Amino acids 4. Write down the nucleotide sequence of t-RNA using the principle of complementarity: DNA G A G T G G C G T C A T i-RNA C U C A C C G C A G U A t-RNA G A G U G G C G U C A U Amino acids

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5. Determine the nucleotide sequence of a protein molecule using the genetic code table. Rules for using the table are given in the exam material. For the CC codon the amino acid LEI corresponds, for the ACC codon the amino acid TPE corresponds. Further work progresses according to plan. 6. DNA G A G T G G C G T C A T i-RNA C U C A C C G C A G U A t-RNA G A G U G G C G U C A U Amino acids le tre ala val Mission completed

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Task 2. Determine the nucleotide sequence of the mRNA, t-RNA anticodons and the amino acid sequence of the corresponding fragment of the protein molecule (using the genetic code table), if the fragment of the DNA chain has the following nucleotide sequence: GTGCCGTCAAAA. Task 27. Cytology task. Protein biosynthesis

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Solution algorithm 1. Read the task carefully. Determine what needs to be done. 2. Make a note according to the plan: DNA G T G C C G T C A A A A i-RNA t-RNA Amino acids 3. Write down the sequence of the i-RNA chain. To do this, use the principle of complementarity (cytosine - guanine, adenine - uracil) DNA G T G C C G T C A A A A i-RNA C A C G G C A G U U U U t-RNA Amino acids 4. Write down the nucleotide t-RNA sequence using the principle of DNA complementarity G T G C C G T C A A A A i-RNA C A C G G C A G U U U U t-RNA G U G C C G U C A A A A Amino acids 5. Determine the nucleotide sequence of a protein molecule using the genetic code table. Rules for using the table are given in the exam material. Remember the table of the Genetic Code and RNA.

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For the CAC codon the amino acid GIS corresponds, for the GHC codon the amino acid GLI corresponds, for AGU - SER, for UUU - FEL 6. DNA G T G C C G T C A A A A i-RNA C A C G C A G U U U U t-RNA G U G C C G U C A A A A Amino acids his gly ser fen Task completed

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Task 3. The nucleotide sequence of the DNA chain fragment is AATGCAGGTCAC. Determine the sequence of nucleotides in mRNA and amino acids in a polypeptide chain. What will happen in a polypeptide if, as a result of a mutation in a gene fragment, the second triplet of nucleotides is lost? Use the genetic code table Task 27. Cytology task. Protein biosynthesis

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Solution algorithm 1. Read the task carefully. Determine what needs to be done. 2. Record according to plan. DNA A A T G C A G G T C A C i-RNA U U A C G U C C A G U G Amino acids Ley Arg Pro Val 3. The task does not say that it is necessary to determine t-RNA, therefore, immediately determine the amino acid sequence. 4. Determine the amino acid sequence when the second triplet of nucleotides is lost. The amino acid sequence will look like: Leu - Pro - Val.

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Task 4. A fragment of a DNA chain has the nucleotide sequence AGGTTCACCCA. During the mutation process, the fourth nucleotide is changed to "G". Determine the nucleotide sequence in the original and modified mRNA, as well as the amino acid sequence in the original and modified protein. Will the composition and properties of the new protein change? Task 27. Cytology task. Protein biosynthesis

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Solution algorithm 1. Read the task carefully. Determine what needs to be done. 2. Record according to plan. DNA A G G T T C A C C C G A i-RNA U C C A G U G G G C U Amino acids Ser Lys Tri Ala 3. The task does not say that it is necessary to determine t-RNA, therefore, immediately determine the amino acid sequence. 4. According to the assignment, the fourth nucleotide is changed to “G”, we make the change and determine the sequence of mRNA and amino acids in the new protein. DNA A G G G T C A C C C G A i-RNA U C C C A G U G G G C U Amino acids Ser Gln Tri Ala The amino acid sequence in the protein molecule has changed, therefore the function performed by this protein will change. Mission completed

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Task 5. T-RNAs with anticodons participated in protein biosynthesis: UUA, GGC, CGC, AUU, CGU. Determine the nucleotide sequence of the section of each chain of the DNA molecule that carries information about the polypeptide being synthesized, and the number of nucleotides containing adenine, guanine, thymine, cytosine in a double-stranded DNA molecule. Task 27. Cytology task. Protein biosynthesis

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Solution algorithm 1. Read the task carefully. Determine what needs to be done. 2. Record according to plan. t-RNA UUA, GGC, CGC, AUU, CGU and – RNA AAU CCG GCG UAA GCA 1st DNA TTA GGC CGC ATT CTG 2nd DNA AAT CCG GCG TAA GCA 3. Count the number of adenines, cytosines, thymines and guanines. A-T = 7 G-C = 8 Task completed

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Task 27. Cytology task. Cell division Types of problems Determining the number of chromosomes and DNA molecules in various phases of mitosis or meiosis. Determination of the set of chromosomes of cells formed at certain stages of gametogenesis in animals or plants. Determining the set of chromosomes of plant cells of different origins To solve problems, it is necessary to know the processes that occur with chromosomes when preparing a cell for division; events that occur to chromosomes during the phases of mitosis and meiosis; the essence of mitosis and meiosis; gametogenesis processes in animals; plant development cycles

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Task 27. Cytology task. Cell division Recommendations: Read the problem statement carefully. Determine what method of cell division is being discussed in the problem. Recall the events of the fission phases discussed in the problem. If the problem contains quantitative data, count and record the number of chromosomes and DNA molecules for each stage

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Problem 1. Drosophila somatic cells contain 8 chromosomes. Determine the number of chromosomes and DNA molecules in prophase, anaphase and after the completion of the telophase of mitosis. Explain the results obtained Solution algorithm 1) When preparing a cell for division, DNA replication occurs, the number of chromosomes does not change, the number of DNA molecules increases by 2 times, so the number of chromosomes is 8, DNA molecules are 16. 2) In the prophase of mitosis, chromosomes spiral, but their number does not change, therefore the number of chromosomes is 8, DNA molecules are 16. 3) In the anaphase of mitosis, the chromatids of the chromosomes diverge to the poles, each pole has a diploid number of single-chromatid chromosomes, but the separation of the cytoplasm has not yet occurred, therefore, in total, there are 8 chromosomes and 16 DNA molecules in the cell. 4) The telophase of mitosis ends with the division of the cytoplasm, so each resulting cell has 8 chromosomes and 8 DNA molecules. Task 27. Cytology task. Cell division

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Task 27. Cytology task. Cell division Problem 2. In cattle, somatic cells have 60 chromosomes. Determine the number of chromosomes and DNA molecules in ovarian cells during oogenesis in interphase before the start of division and after division of meiosis I. Explain the results obtained at each stage. Solution algorithm 1) before division begins in interphase, DNA molecules double, their number increases, but the number of chromosomes does not change - 60, each chromosome consists of two sister chromatids, so the number of DNA molecules is 120; number of chromosomes - 60; 2) meiosis I is a reduction division, therefore the number of chromosomes and the number of DNA molecules decreases by 2 times, therefore after meiosis I the number of chromosomes is 30; number of DNA molecules - 60.

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Task 27. Cytology task. Cell division Problem 3. A somatic cell of an animal is characterized by a diploid set of chromosomes. Determine the chromosome set (n) and the number of DNA molecules (c) in the cell nucleus during gametogenesis in metaphase I of meiosis and anaphase II of meiosis. Explain the results in each case. Solution algorithm 1) In metaphase I of meiosis, the set of chromosomes is 2n, the number of DNA is 4c 2) In anaphase II of meiosis, the set of chromosomes is 2n, the number of DNA is 2c 3) Before meiosis (at the end of interphase), DNA replication occurred, therefore, in metaphase I Meiosis the number of DNA is doubled. 4) After the first reduction division of meiosis in anaphase II of meiosis, sister chromatids (chromosomes) diverge to the poles, therefore the number of chromosomes is equal to the number of DNA.