MCQOPTIONS
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MCQOPTIONS
This section includes 107 Mcqs, each offering curated multiple-choice questions to sharpen your Biochemistry knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
Which of the following is an active site on its single polypeptide chain for DNA Polymerase I? |
| A. | 5' 3' polymerase |
| B. | 3' 5' exonuclease |
| C. | 5' 3' exonuclease |
| D. | all of the above |
| Answer» B. 3' 5' exonuclease | |
| 52. |
If one cell has AT contents 40%, what will be the percentage of Guanine residue? |
| A. | 60% |
| B. | 15% |
| C. | 30% |
| D. | Guanine residue can not be calculated |
| Answer» D. Guanine residue can not be calculated | |
| 53. |
In an agarose gel, DNA is moving from |
| A. | cathode to anode |
| B. | left to right |
| C. | anode to cathode |
| D. | A to B |
| Answer» B. left to right | |
| 54. |
Which of the following is not a structural motif in DNA binding proteins? |
| A. | bZIP |
| B. | helix-turn-helix |
| C. | TFIID |
| D. | zinc finger |
| Answer» D. zinc finger | |
| 55. |
DNA with a G-C content of 50% will melt at approximately |
| A. | 60 C |
| B. | 70 C |
| C. | 90 C |
| D. | 100 C |
| Answer» D. 100 C | |
| 56. |
DNA replication in eukaryotes occurs only in |
| A. | G1 phase |
| B. | S phase |
| C. | G2 phase |
| D. | M phase |
| Answer» C. G2 phase | |
| 57. |
Which of the following is used to determine the appropriate stringency (Wallace rule)? |
| A. | Tm = 2 x (No.of G:C base pair) + 4 x (No.of A:T base pair) |
| B. | Tm = 4 x (No.of A:T base pair) + 2 x (No.of G:C base pair) |
| C. | Tm = 4 x (No.of G:C base pair) + 2 x (No.of A:T base pair) |
| D. | Tm = 69.3 + 0.41 (%)G+C -650/1 |
| Answer» D. Tm = 69.3 + 0.41 (%)G+C -650/1 | |
| 58. |
DNA polymerases I also has |
| A. | 5'-3' exonuclease activity |
| B. | 3'-5'exonuclease activity |
| C. | both (a) and (b) |
| D. | 5'-3' endonuclease activity |
| Answer» C. both (a) and (b) | |
| 59. |
Who's X-ray work aided Watson and Crick in their discovery of the double helix? |
| A. | W.H. Bragg |
| B. | R. Franklin |
| C. | L. Pauling |
| D. | Leaderberg |
| Answer» C. L. Pauling | |
| 60. |
What is the IUPAC code for an A, C, T ambiguity in a nucleic acid sequence? |
| A. | B |
| B. | H |
| C. | S |
| D. | None of these |
| Answer» C. S | |
| 61. |
Reverse transcriptase produces |
| A. | DNA from peptides |
| B. | RNA from DNA |
| C. | RNA from RNA |
| D. | DNA from RNA |
| Answer» E. | |
| 62. |
What is the approximate percentage of repetitive DNA sequences in human DNA? |
| A. | 10 to 20% |
| B. | 20 to 30% |
| C. | 30 to 40% |
| D. | 40 to 50% |
| Answer» C. 30 to 40% | |
| 63. |
The nicks or gaps between Okazaki fragments are eventually sealed by |
| A. | gyrase |
| B. | DNA ligase |
| C. | RNA ligase |
| D. | polymerase |
| Answer» C. RNA ligase | |
| 64. |
The replication of a linear DNA molecule in a eukaryotic chromosome creates a problem which is reported to be sorted out by |
| A. | using enzyme called telomerase |
| B. | shortening of the double stranded replicated portion |
| C. | using RNA as a template |
| D. | none of the above |
| Answer» B. shortening of the double stranded replicated portion | |
| 65. |
The rapid appearance of HIV-1 strains that are resistant to AIDS drugs is due in part to which of the following property of its reverse transcriptase? |
| A. | AZT (zidovudine) is too expensive to be taken in effective doses |
| B. | The RNase H domain of p66 causes error prone synthesis |
| C. | It lacks a proofreading exonuclease |
| D. | It has low affinity for the correct dNTP's |
| Answer» D. It has low affinity for the correct dNTP's | |
| 66. |
DNA replication results in |
| A. | two completely new DNA molecules |
| B. | two DNA molecules such that each one contains a strand of the original |
| C. | one new DNA molecules 1 old molecule |
| D. | one new molecule of RNA |
| Answer» C. one new DNA molecules 1 old molecule | |
| 67. |
Which enzyme catalyzes the elongation of DNA molecules? |
| A. | DNA polymerase |
| B. | Helicase |
| C. | DNA ligase |
| D. | Primase |
| Answer» B. Helicase | |
| 68. |
There is a single origin for DNA replication in bacteria. How many origins of replication are found in the much larger genomes of eukaryotes such as mammals? |
| A. | One |
| B. | About 100 |
| C. | Thousands and tens of thousands |
| D. | none of these |
| Answer» D. none of these | |
| 69. |
What is the exact name of the classical Watson-Crick double helix DNA? |
| A. | A-DNA |
| B. | B-DNA |
| C. | Z-DNA |
| D. | X-DNA |
| Answer» C. Z-DNA | |
| 70. |
The melting of 40-45 bp at the oriC site of E. coli requires |
| A. | DNA + ATP + HU |
| B. | DNA + ATP + HU + DNAb |
| C. | DNA+ ATP + HU + DNAb + DNAa |
| D. | DNA + ATP + HU + DNAb + DNAa + Pol III holoenzyme |
| Answer» B. DNA + ATP + HU + DNAb | |
| 71. |
For the DNA replication in eukaryotes, the cell cycle consists of |
| A. | G1, G2 and M phases |
| B. | S, G2 and M phases |
| C. | G1,S, G2 and M phases |
| D. | G2 and M phases |
| Answer» D. G2 and M phases | |
| 72. |
Which will require a higher temperature to denature? |
| A. | DNA with a high G-C content |
| B. | DNA with a high A-T content |
| C. | RNA with a high G-C content |
| D. | RNA with a high A-T content |
| Answer» B. DNA with a high A-T content | |
| 73. |
TM refers to the temperature at which |
| A. | membranes are 50% fluid |
| B. | 50% of a DNA molecule is denatured |
| C. | 50% of a protein molecules are denatured |
| D. | all of the above |
| Answer» E. | |
| 74. |
The DNA is negatively super coiled, complexes to histone, |
| A. | HU |
| B. | HSP-1 |
| C. | H-NS |
| D. | All of these |
| Answer» E. | |
| 75. |
DNA segments capable of moving from one place in the genome to another is known as |
| A. | transposons |
| B. | retrovirus |
| C. | introns |
| D. | moving elements |
| Answer» B. retrovirus | |
| 76. |
What does ligase do during replication of DNA? |
| A. | Synthesizes the lagging strand |
| B. | Makes copies of mRNA from DNA |
| C. | Joins nicks in DNA strands |
| D. | Digests mRNA when it is no longer needed |
| Answer» D. Digests mRNA when it is no longer needed | |
| 77. |
The site on a bacterial chromosome that marks the initiation point for chromosome replication is called |
| A. | <i>Ori</i> |
| B. | a promoter |
| C. | <i>Pro</i> |
| D. | an initiation codon |
| Answer» B. a promoter | |
| 78. |
The B-DNA structure found in solution is a |
| A. | left-handed double helix of antiparallel chains (10 bp/turn) |
| B. | right-handed double helix of antiparallel chains ( 10 bp/turn) |
| C. | left-handed zig-zag helix of antiparallel chains (10 bp/turn) |
| D. | right-handed double helix of parallel chains ( 10 bp/turn) |
| Answer» C. left-handed zig-zag helix of antiparallel chains (10 bp/turn) | |
| 79. |
Which of the following in DNA replication and transcription are common? |
| A. | incorporation of deoxynucleotides |
| B. | utilization the same enzyme |
| C. | synthesis in the 5'-3' direction |
| D. | none of the above |
| Answer» D. none of the above | |
| 80. |
An important difference between eukaryotic and prokaryotic DNA replication is |
| A. | eukaryotic DNA polymerases are faster |
| B. | more DNA polymerases are found in eukaryotes |
| C. | multiple origins of replication in eukaryotes |
| D. | RNA primers are not required in eukaryotes |
| Answer» D. RNA primers are not required in eukaryotes | |
| 81. |
In DNA, nucleotides are covalently joined together by |
| A. | 3', 5' phosphodiester bonds to form a repetitive sugar-phosphate chain |
| B. | 2', 5' phosphodiester bonds to form a repetitive sugar-phosphate chain |
| C. | 2', 3' phosphodiester bonds to form a repetitive sugar-phosphate chain |
| D. | 3', 4' phosphodiester bonds to form a repetitive sugar-phosphate chain |
| Answer» B. 2', 5' phosphodiester bonds to form a repetitive sugar-phosphate chain | |
| 82. |
What is the name given to the points at which a DNA helix is unwound and new strands develop? |
| A. | Replication origins |
| B. | Replication forks |
| C. | Leading strands |
| D. | Okazaki fragments |
| Answer» C. Leading strands | |
| 83. |
First evident that DNA is genetic material comes from the experiment of Griffith is |
| A. | transduction |
| B. | transformation |
| C. | replication |
| D. | translation |
| Answer» C. replication | |
| 84. |
An RNA primer is synthesized by |
| A. | DNA helicases |
| B. | ligase |
| C. | DNA topoisomerase |
| D. | primase |
| Answer» E. | |
| 85. |
Overwinding or overtightening of DNA during replication is caused and removed by |
| A. | DNAb, DNA polymerase |
| B. | DNAa, gyrase |
| C. | DNAb, gyrase |
| D. | Single stranded protein, DNAa |
| Answer» D. Single stranded protein, DNAa | |
| 86. |
How does ethidium bromide interact with DNA? |
| A. | It binds to adenine |
| B. | It binds to phosphate |
| C. | It intercalates between bases |
| D. | It does not interact |
| Answer» D. It does not interact | |
| 87. |
Nucleosome is |
| A. | an octamer of four histones with H1 protein |
| B. | an hexamer of three histones with H1 protein |
| C. | an hexamer of three histones without H1 protein |
| D. | an octamer of four histones without H1 protein |
| Answer» E. | |
| 88. |
The DNA polymerase in bacteria, responsible for DNA synthesis is |
| A. | Polymerase I |
| B. | Polymerase II |
| C. | Polymerase III |
| D. | all of these |
| Answer» D. all of these | |
| 89. |
In a typical electrophoresis experiment, larger fragments of DNA move more |
| A. | slowly, so they appear nearer the top of a gel photograph |
| B. | quickly, so they appear nearer the top of a gel photograph |
| C. | slowly, so they appear nearer the bottom of a gel photograph |
| D. | quickly, so they appear nearer the bottom of a gel photograph |
| Answer» B. quickly, so they appear nearer the top of a gel photograph | |
| 90. |
Which of these drugs bind to DNA and cuts it, producing hydroxyl radicals? |
| A. | Bleomycin |
| B. | Erythromycin |
| C. | Tunicamycin |
| D. | All of these |
| Answer» B. Erythromycin | |
| 91. |
Automated DNA sequencing uses the chain termination method |
| A. | but with an oligonucleotide primer labeled with a fluorescent dye |
| B. | but with a polynucleotide primer labeled with a fluorescent dye |
| C. | with no primer |
| D. | either (b) or (c) |
| Answer» B. but with a polynucleotide primer labeled with a fluorescent dye | |
| 92. |
Okazaki fragments occur on the __________ and are bonded together by __________ |
| A. | Leading strand, polymerase |
| B. | mRNA, anticodons |
| C. | Lagging strand, ligase |
| D. | tRNA, polymerase |
| Answer» D. tRNA, polymerase | |
| 93. |
The packing ratio of nucleosomes is about |
| A. | 6 |
| B. | 8 |
| C. | 7 |
| D. | 9 |
| Answer» D. 9 | |
| 94. |
After one replication in 15N, how many bands should be observed in a cesium chloride gradient? |
| A. | One |
| B. | Two |
| C. | Three |
| D. | A smear |
| Answer» B. Two | |
| 95. |
The RNA primers used to initiate replication in E. coli |
| A. | result in Okazaki fragments on leading strand |
| B. | are removed by Pol I |
| C. | are joined together by DNA ligase |
| D. | are removed by helicase + ATP |
| Answer» C. are joined together by DNA ligase | |
| 96. |
Which of the following species lack a 'classical' histone H1? |
| A. | <i>Saccharomyces cerevisiae</i> |
| B. | <i>Strongylocentrotus purpuratus</i> |
| C. | <i>Xenopus laevis</i> |
| D. | <i>Arabidopsis thaliana</i> |
| Answer» B. <i>Strongylocentrotus purpuratus</i> | |
| 97. |
Which of the following are short nucleotides strands made by DNA polymerase working in the opposite direction of the replication fork? |
| A. | Leading strands |
| B. | Okazaki fragments |
| C. | Primers |
| D. | Lagging strand |
| Answer» C. Primers | |
| 98. |
The role of primase is to |
| A. | dismantle RNA primer |
| B. | cleave and unwinds short sections of DNA ahead of the replication fork |
| C. | proofread base pairing |
| D. | synthesize an RNA primer to begin the elongation process |
| Answer» E. | |
| 99. |
Which polymerase is active in DNA repairing |
| A. | Polymerase I |
| B. | Polymerase II |
| C. | Polymerase III |
| D. | none of these |
| Answer» C. Polymerase III | |
| 100. |
Each replication bubbles consists of |
| A. | 3 replication forks |
| B. | 2 replication forks |
| C. | 4 replication forks |
| D. | 1 replication forks |
| Answer» C. 4 replication forks | |