151. Skin color is the aggregate result of the expression of a number of genes modified by ethnic origin and genetic inheritance. What can cause the hypopigmentation?

Answer: Excess phenylalanine inhibits tyrosinase the first step toward melanin production, thus resulting in hypopigmentation. Excess melanin leads to hyperpigmentation. Melatonin is a hormone involved in the sleep cycle. Excessive stimulation of tyrosinase would lead to more melanin and therefore hyperpigmentation. Para-hydroxyphenylpyruvate means less transamination and perhaps more tyrosine converted to melanin and hyperpigmentation.

152. Name types of deamination od amino acids:

1

2

3

4

Answer: 1. - reductive deamination, 2 - hydrolytic deamination, 3 - reductive, 4 – oxidative.

153. Complete the chemical equation of the reachtion:

Answer:

1 54. Name enzymes of urea cycle :

Answer: 1. Ornithine transcarbamylase, 2. Argininosuccinate Synthase, 3. Argininosuccinase lyase, 4. Arginase.

155. Name the enzyme, which catalises this reaction:

Answer: Phenylalanine hydroxylase

Section VII Principles of molecular biology and molecular genetics

1. Indicate nitrogenous base which is a specific component of ribonucleoproteins

1. Uracil

2. Adenine

3. Guanine

4. Thymine

5. Cytosine

2. What proteins are obvious constituents of nucleoproteins?

1. Histones and protamins

2. Albumin and globulins

3. Dynein and kinesin

4. Prolamin and glutelin

5. Cytochromes b₅ and c

3. How is called elementary monomer of polymer chain of nucleic acids?

1. Mononucleotide

2. Nucleoside

3. Amino acid

4. Nitrogenous base

5. Ribosyl-3-phosphate

4. Note the complementary to cytosine nitrogenous base in DNA double helix according to Watson and Crick model

1. Guanine

2. Adenine

3. Uracil

4. Thymine

5. Xanthine

5. One step of DNA double helix in B-form contains the next number of base pairs:

A. 10

B. 15

C. 13

D. 7

E. 20

6. How many hydrogen bonds support a complementary base pair A-T?

A. 2

B. 1

C. 3

D. 5

E. 7

7. What type of chemical bonds joins together mononucleotides in RNA chain?

1. Phosphodiester bonds

2. Hydrogen

3. Ionic

4. Coordinative

5. Hydrophobic interactions

8. The base sequence of a segment of DNA is pCpApGpTpTpApGpC. Indicate a complementary sequence.

1. pGpTpCpApApTpCpG

2. pGpCpTpApApCpTpG

3. pCpGpApTpTpGpApC

4. pTpApGpCpCpApGpT

5. pCpApGpTpTpApGpC

9. If the cytosine content of double-helical DNA is 20 mole% of the total bases, the adenine content would be:

1. 30 mole%

2. 10 mole%

3. 20 mole%

4. 40 mole%

5. 50 mole%

10. Which scientists first gave experimental evidence that DNA is the genetic material?

1. Avery, MacLeod, and McCarty who repeated the transformation experiments of Griffith, and chemically characterized the transforming principle.

2. Garrod, who postulated that Alcaptonuria, or black urine disease, was due to a defective enzyme.

3. Beadle and Tatum, who used a mutational and biochemical analysis of the bread mold Neurospora to establish a direct link between genes and enzymes.

4. Meselson and Stahl who showed that DNA is replicated semiconservatively.

5. Watson and Crick who gave a model for the structure of DNA

11. The core of nucleosome is composed from the next types of histones:

1. H2a,H2b,H3,H4

2. H1,H2a, H2b, H3

3. H1,H3,H4

4. H2a,H2b,H2c,H2d

5. H1,H2,H3,H4

12. A sample of some substance was submitted to hydrolysis; in hydrolysate were detected organic bases of purine and pyrimidine classes, ribose and phosphates, amino acids. What substance was most probably taken for investigation?

A. Ribonucleoprotein

B. Chromoproterin

C. Phosphoproterin

D. Deoxyrybonucleoprotein

E. Glycoprotein

13. To which of the following does thymine form hydrogen bonds in DNA?

1. adenine

2. thymine

3. Cytosine

4. guanine

5. Uracil

14. Which of these organelles contains DNA?

1. Mitochondria

2. Golgi apparatus

3. Lysosomes

4. Rough endoplasmic reticulum

5. Smooth endoplasmic reticulum

15. In a double stranded molecule of DNA, the ratio of purines: pyrimidines is:

1. Always 1:1

2. Variable

3. Determined by the base sequence in RNA

4. Genetically determined

5. Determined by the number of purines in the sense strand of the DNА

16. In which of the following molecules would you find an anticodon?

1. transfer RNA

2. messenger RNA

3. ribosomal RNA

4. small nuclear RNA

5. Heterogenous RNA

17. How many hydrogen bonds support a complementary base pair G-C?

1. 3

2. 7

3. 5

4. 1

5. 2

18. Nucleic acids absorb ultraviolet light in 250-270 nm regions. This property is determined by the next chemical structures:

1. Nitrogenous bases

2. Hydrogen bonds

3. Ribose

4. Phosphoric acid

5. Phosphodiester bonds

19. Which of the following nucleotide bases is not found in iRNA?

1. Thymine

2. Adenine

3. Uracil

4. Guanine

5. Cytosine

20. Which of the following molecules does not form part of DNA?

1. Amino acid

2. Purine

3. Pyrimidine

4. Deoxyribose

5. Phosphate

21. Which of the following statements is true of double-helical DNA?

1. The 3’ hydroxyl groups of each chain are at opposite ends of the molecule

2. The planes of the bases lie parallel to the helix axis

3. The chains have a backbone of linked glycosides

4. The step of B-helix contain 12 base pairs

5. The duplex structure is stabilized by hydrophobic interactions between bases

22. With what mRNA codon would the tRNA in the diagram be able to form a codon-anticodon base pairing interaction?

A. 3'-AUG-5'

B. 3'-GUA-5'

C. 3'-CAU-5'

D. 3'-UAC-5'

E. 3'-UAG-5'

23. Radiolabelled H3-thymidine was introduced to cell culture medium. In which cell organelles will be detected H³-label thereafter?

1. Nucleus

2. Ribosomes

3. Golgi apparatus

4. Lysosomes

5. Endoplasmic reticulum

24. Which of the following statements concerning characteristics of histones is true?

1. They are acidic proteins located in the nucleus

2. They are covalently linked to single-stranded DNA

3. Evolutionary they are highly conserved proteins

4. They are large proteins with mol weight more then 100 KDa

5. They have no post-translationally modified amino acids

25. Nitrosamines belong to deaminating mutagens. From what nitrogene base does uracyl appears as a result of their action?

1. Cytosine

2. Adenine

3. Guanine

4. Thymine

5. Methyluracil

26. Which of the following is an accurate statement concerning the differences between DNA and RNA?

1. RNA lacks the base thymine (which is found in DNA) and has uracil instead

2. RNA is usually double-stranded, but DNA is usually single-stranded.

3. RNA has the sugar deoxyribose, but DNA has the sugar ribose.

4. RNA contains three different nucleotides, but DNA contains four different nucleotides.

27. Orotic acid is an intermediate in biosynthesis of the following nitrogenous base:

1. Cytosine

2. Hypoxanthine

3. Adenine

4. Guanine

5. Xanthine

28. The activity of xanthine oxidase is dependent from the next coenzyme:

1. FAD

2. NAD

3. FMN

4. CoA-SH

5. NADP

29. Which of the following contribute N to both purine and pyrimidine:

1. Aspartic acid.

2. Glutamic acid.

3. Glycine.

4. Arginine.

5. Ammonia.

30. Formation of thymidine nucleotides, which are used for the biosynthesis of DNA, begins from dUDP, which on the first stage is hydrolised to dUMP, and thereafter methylated. What compound serves as the donor of methyl groups?

1. Methylenetetrahydrofolate

2. Choline

3. Lecithin

4. Methionine

5. Carnitine

31. In reaction of transformation of ribose to deoxyribose in course of deoxyribonucleotide production for DNA biosynthesis participates a low molecular weight protein thioredoxine. It contains two SH groups, which in course of reaction are oxidized. What coenzyme is used in restoration of reduced form of thioredoxine?

A. NADP H₂

B. Glutathion

C. Coenzyme Q

D. NAD H₂

E.AMP

32. Biosynthesis of what mononucleotide is arrested under the influence of 5-fluorouracil?

A.dTMP

B.dUMP

C.dCMP

D.dIMP

E.dAMP

33. The smallest unit of DNA capable of coding for the synthesis of a polypeptide is:

1. Cistron

2. Operon

3. Repressor gene

4. Replicon

5. Terminator

34. mRNA is complementary to the nucleotide sequence of:

1. Coding strand

2. Ribosomal RNA

3. tRNA

4. Template strand

5. snRNA

35. All pribnow boxes are variants of the sequence:

1. 5′–TATAAT –3′

2. 5′–GAGCCA –3′

3. 5′–UAACAA –3′

4. 5′–TCCTAG –3′

5. 5′–UCCUAG –3′

36. From nitrates, nitrites and nitrosamines in the body is produced nitrose acid, which cause oxidative deamination of nitrogeneous bases of nucleotides. This may lead to a point mutation by change of cytosine to one of the next base:

A. Uracil

B. Thymine

C. Adenine

D. Guanine

E. Inosine

37. 5’-Terminus of mRNA molecule is capped with;

1. 7-Methylguanosine triphophate

2. Guanosine triphosphate

3. Adenosine triphosphate

4. Adenosine diphosphate

5. Adenosine monophosphate

38. Which of the following statements best describe the action of introns?

A. They are excised upon processing of heterogeneous nuclear RNA to messenger RNA

B. They are retained upon processing of ribosomal RNA

C. They are spacer sequences

D. They are added to mRNA during the plicing reaction.

39. Okazaki fragments are formed during the synthesis of:

1. DNA

2. mRNA

3. tRNA

4. rRNA

5. Proteine

40. Reverse transcriptase is capable of synthesis:

1. RNA → DNA

2. DNA → RNA

3. RNA → RNA

4. DNA → DNA

5. Protein → DNA

41. Synthesis of DNA is also known as:

1. Replication

2. Duplication

3. Transcription

4. Translation

42. In the treatment of infection diseases are used antibiotics streptomycine, neomycine, kanamycine. What step of protein synthesis in bacterial cell they inhibit?

1. Translation

2. Replication

3. Transcription

4. mRNA processing

5. Splicing

43. What enzyme is used for synthesis of genes from template RNA or DNA in gene engineering? (This enzyme was discovered in some RNA containing viruses).

A. Revertase

B. Exonuclease

C. Endonuclease

D. Topoisomerase I

E. Helicase

44. Genetic information is stored in DNA, which does not participate directly in protein synthesis in the cell. What process provides the transformation of genetic information into amino acid sequence of polypeptide chain?

1. Translation

2. Transcription

3. Translocation

4. Replication

5. Splicing

45. In post-translation modification of nascent protein chain are involved the next proteins:

1. Chaperons 60 K

2. Cathepsins

3. Caspases

4. Cytochrome c

5. Ubiquitin

46. What amino acid is coded by the triplet of bases AUG?

1. Methionine

2. serine

3. tyrosine

4. cysteine

5. Valine

47. Which of the following toxins inhibits eukaryotic protein synthesis through the depurination of a single adenine residue in 28 s ribosomal RNA?

1. Diphtheria toxin

2. Ricin

3. Sarcin

4. Puromycin

5. Cycloheximide

48. The genetic code refers to which one of the following?

1. The nucleotide sequences that correspond to common amino acids

2. The number of chromosomes in the diploid cells of the species

3. The amino acid sequence of cellular proteins

4. The ratios of Mendelian inheritance

5. The hierarchy of DNA, RNA and protein

49. The translation of mRNA into the amino acid sequence of a polypeptide in prokaryotes is terminated at the end of the message by one of the three stop codons in the mRNA chain. The stop codon is recognized by:

1. A specific protein

2. A specific uncharged tRNA

3. A specific aminoacyl-tRNA

4. A specific ribosomal RNA

5. A specific ribosomal subunit

50. The inherited information is saved in DNA, though directly in the synthesis of protein in a cell it does not participate. What process provides the realization of the inherited information in a polypeptide chain?

1. Translation

2. Transcription

3. Translocation

4. Replication

5. Transformation

51. Glycosylation of proteins after completion of their synthesis in ribosomes proceeds in the next cell compartment:

1. Golgi vesicles

2. Mitochondria

3. Lysosomes

4. Proteasomes

5. Ribosomes

52. Redundancy of the genetic code means that:

1. A given base triplet can code for more then one amino acid

2. There is no punctuation in the code sequences

3. The third base in codon is not important in coding

4. A given amino acid can be coded for by more then one base triplet

5. Codons are not ambiguous

53. Restrictases are enzymes of bacterial origin, which are used in recombinant DNA technology. They belong to the next class of enzymes:

1. Hydrolases

2. Oxido-reductases

3. Transferases,

4. Liases

5. Isomerases

54. The next technique is used for multiple amplification of distinct and selected segment of DNA:

1. Polymerase chain reaction (PCR)

2. DNA fingerprint analysis

3. Southern blot analysis

4. Northern blot analysis

5. Restriction fragment length polymorphism (RFLP) analysis

55. For the formation of the transport form of amino acid during the protein synthesis in ribosomes. is required.

A. tRNA.

B. Revertase.

C. GTP.

D. mRNA.

E. Ribosome

56. In case of poisoning by amanitine, a death-cup mushroom toxin, RNA-polymerase B (II) is blocked. This leads to the blockage of:

A. Processing of mRNA.

B. Synthesis of tRNA.

C. Reverse transcription.

D.Synthesis of primers.

E. Synthesis of mRNA.

57. Degeneration of the genetic code is the ability of more than one triplet to encode a single amino acid. Which amino acid is encoded by only one triplet?

A. Methionine.

B. Serine.

C. Alanine.

D. Leucine.

E. Lysine.

58. A human genome contains about 30000 genes, and the amount of variants of antibodies reaches millions. What mechanism is used for the formation of new genes that are responsible for the synthesis of such amount of antibodies?

A. Recombination of genes.

B. Amplification of genes.

C. Replication of DNA.

D. Reparation of DNA.

E. Formation of Okazaki fragments.

59. Choose from the following a potent inhibitor of transcription:

A. Actinomycin D

B. Steptomycin

C. Kanamycin

D. Doxorubicin

E. Actinorodin

60. Indicate a specific feature of transcription in prokaryotes:

1. All of the above

2. mRNA transcript is used directly for translation without modification.

3. Since prokaryotes lack a nucleus, mRNA also is translated on ribosomes before it is transcribed completely (i.e., transcription and translation are coupled).

4. Prokaryote mRNAs are polycistronic, they contain amino acid coding information for more than one gene.

61. What is not typical for transcription of eukaryotes?

1. mRNA transcript is used directly for translation without modification

2. mRNA transcript is not mature (pre-mRNA); must be processed.

3. Transcription and translation are not coupled (mRNA must first be exported to the cytoplasm before translation occurs).

4. Eukaryote mRNAs are monocistronic, they contain amino acid sequences for just one gene.

62. Indicate function of snRNA (small nuclear RNA):

1. It forms complexes with proteins used in eukaryotic RNA processing (e.g., exon splicing and intron removal).

2. It forms complexes called ribosomes with protein, the structure on which mRNA is translated.

3. It binds to 3’ UTR target mRNAs and result in silencing.

4. It encodes the amino acid sequence of a polypeptide.

63. The genetic code is brought by the?

1. mRNA

2. DNA

3. snRNA

4. siRNA

5. rRNA

64. Active translation always occurs on:

1. Polysomes

2. Lysosomes

3. Liposomes

4. Inner membrane of mitochondria

65. Escherichia coli 70S ribosome model consists from:

1. 50S subunit and 30S subunit

2. 50S subunit and 20S subunit

3. 50S subunit and 40S subunit

4. 40S subunit and 30S subunit

66. The lac operon is an example of:

1. Transcriptional control

2. Post-transcriptional control

3. Replicational control

4. Transcriptional control

67. In the lac operon, RNA polymerase:

1. Binds to the promoter

2. Binds to the operator

3. Binds to the regulatory gene

4. Is synthesized by the regulatory gene

5. Binds to the regulator protein

68. The promoter region of a bacterial operon:

1. Is a binding site for RNA polymerase

2. Codes for repressor proteins

3. Codes for inducer substances

4. Codes for corepressor substances

5. Is binding site for inducers

69. The regulatory gene of bacterial operon:

1. codes for repressor proteins

2. codes for repressor proteins

3. acts as an on-off swith for the structural genes

4. is a binding site for RNA polymerase

5. is a binding site for inducers

70. The sugar lactose induces synthesis of the enzyme lactase. What happens when E. coli cells run out of lactose?

1. Repressor protein binds to the operator.

2. Repressor protein binds to the promoter.

3. RNA polymerase attaches to the promoter.

4. RNA polymerase attaches to the repressor.

72. In the lactose operon system in E. coli, the repressor is:

1. A protein

2. A product of a structural gene

3. Bound to the promoter sequence

4. Lactose

5. A short length of DNA

73. Which of the following statements concerning the regulatory gene associated with the lac operon is correct?

1. mRNA is transcribed from the R gene whether lactose is present or not.

2. mRNA is only transcribed from the R gene when lactose is present.

3. mRNA is only transcribed from the R gene when lactose is not present.

4. Lactose inhibits the translation of R gene mRNA.

5. Lactose binds to the promoter of the lac operon.

74. According to the Jacob-Monod model of gene regulation, inducer substances in bacterial cells probably:

1. Combine with repressor proteins, inactivating them.

2. Combine with operator regions.

3. Combine with structural genes, stimulating them to synthesize messenger RNA.

4. Combine with promoter regions, activating RNA polymerase.

5. Combine with nucleoli, triggering production of more ribosomes.

75. In the tryptophan operon of E. coli the end product of biochemical pathway, tryptophan, binds to the repressor protein which then binds to the:

1. Operator to inhibit transcription

2. Promoter to accelerate transcription

3. Promoter to inhibit transcription

4. Operator to accelerate transcription

5. Repressor gene to accelerate transcription

76. Nucleosomes:

1. both D and E are correct

2. are composed of DNA and histones

3. are small particles found in only the nuclei of plant cells

4. disappear during transcription

5. play a role in coiling and uncoiling the chromosomes

77. An antibody molecule is made up of four polypeptide chains joined together by disulfide bonds. Which one of the following statements concerning these polypeptide chains is correct?

A. All four chains have variable regions

B. Only the two light chains have variable regions

C. Only the two heavy chains have constant regions

D. Only the two heavy chains have variable regions

E. All of four chains are of equal length

78. Which one of the following statements concerning antibodies is correct?

A. Antigens are bound by the variable regions of the antibody molecules.

B. Antibodies are usually proteins but sometimes they are polysaccharides.

C. Each antibody has two chains.

D. The heavy but not the light, chains of the antibody molecule have variable and constant regions.

E. The tail region is important in antigen specificity.

79. Fragments of DNA containing one or several genes and a control element that can move from one part of the genome to another are called:

A. Transposons

B. Exons.

C. Introns.

D. Plasmids.

E. Promoters

80. Genes and\or exons can be duplicated by all of the following exept:

A. mRNA processing in the nucleus.

B. Reverse transcription.

C. Transposition.

D. Unequal crossing over during meiosis.

E. Breakage and fusion during meiosis.

81. Which statement about antibodies is false?

A. Human blood contains high levels of circulating antibodies against all positive antigens.

B. Two sites on each antibody molecule can bind antigen.

C. Antibodies are globulin proteins.

D. Antibodies are found in vertebrate animals.

E. Each antibody combines with a specific antigen.

82. The enormous variety of antibodies produced by an individual is due to:

A. Excision of genetic material during fatal development and exon removal during mRNA processing.

B. Specific rearrangement of genes in developing lymphocytes induced by antigens in the nucleus.

C. Synthesis of antibodies upon exposure to an antigen using the antigen as a template for antibody formation.

D. Induction of cell division by cross-linking of the antibody molecules.

E. Mutations within the genome.

83. Restriction endonucleases are useful in recombinant DNA technique because they:

A. Cut DNA at specific sites.

B. Restrict the number of nucleotides that can be removed at one time.

C. Restore the bonds in the DNA backbone.

D. Synthesize cDNA from RNA.

E. Can be used to locate genes for mapping.

84. Which one of the following statements is false?

A. Molecules of mRNA are synthesized on the ribosomes from nucleotides brought by tRNA.

B. In base substitution mutations only a single nucleotide of a gene is altered.

C. The nucleolus is a specialized region of a chromosome where tRNA is synthesized.

D. Some amino acids are specified by several “synonymous” codons.