MCQOPTIONS
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MCQOPTIONS
This section includes 267 Mcqs, each offering curated multiple-choice questions to sharpen your Biochemistry knowledge and support exam preparation. Choose a topic below to get started.
| 151. |
DNA gyrase in E. coli |
| A. | adds positive supercoils to chromosomal DNA |
| B. | can be inhibited with antibiotics |
| C. | is required only at the oriC site |
| D. | performs the same function as helicase in eukaryotes |
| Answer» C. is required only at the oriC site | |
| 152. |
In DNA, there are |
| A. | five bases known as adenine, guanine, thymine, tryptophan and cytosine |
| B. | four bases known as adenine, guanine, thymine and cytosine |
| C. | three bases known as adenine, guanine and cytosine |
| D. | only two bases known as adenine and cytosine |
| Answer» C. three bases known as adenine, guanine and cytosine | |
| 153. |
DNA replication takes place in which direction? |
| A. | 3' to 5' |
| B. | 5 'to 3' |
| C. | Randomly |
| D. | Vary from organism to organism |
| Answer» C. Randomly | |
| 154. |
What is the main damaging effect of UV radiation on DNA? |
| A. | Depurination |
| B. | Formation of thymine dimers |
| C. | Single strand break |
| D. | Dehydration |
| Answer» C. Single strand break | |
| 155. |
Proteins involved in opening a replication bubble are |
| A. | DNA helicases |
| B. | single stranded binding proteins |
| C. | ligase |
| D. | DNA topoisomerase |
| Answer» E. | |
| 156. |
The higher order structure of DNA shows symmetry, whereas the higher order structures of most proteins do not. Why isn't protein shape more regular like DNA? |
| A. | DNA has one main function in cells whereas proteins have many. |
| B. | The many different amino acid R groups on proteins confer many different shapes. |
| C. | Some S amino acids cause proteins to bend; others cause protein to flatten. |
| D. | All of the above |
| Answer» E. | |
| 157. |
DNA helicase is used to |
| A. | unwind the double helix |
| B. | interact the double helix closely |
| C. | break a phosphodiester bond in DNA strand |
| D. | none of the above |
| Answer» B. interact the double helix closely | |
| 158. |
Klenow fragment without free nucleotides exhibits |
| A. | exonuclease activity |
| B. | endonuclease activity |
| C. | nickase activity |
| D. | no activity |
| Answer» B. endonuclease activity | |
| 159. |
Which histone(s) are associated with the linker DNA of a nucleosome? |
| A. | Histone H1 |
| B. | Histones H2A and H2B |
| C. | Histone H3 |
| D. | Histone H4 |
| Answer» B. Histones H2A and H2B | |
| 160. |
Okazaki fragments occur during |
| A. | transformation |
| B. | replication |
| C. | polymerase reaction |
| D. | synthesis |
| Answer» C. polymerase reaction | |
| 161. |
DNA can be sequenced by the |
| A. | chemical method |
| B. | chain termination procedure |
| C. | both (a) and (b) |
| D. | physical method |
| Answer» D. physical method | |
| 162. |
E.coli DNA polymerases II and III lack |
| A. | 5' → 3' exonuclease activity |
| B. | 5' → 3' endonuclease activity |
| C. | partially 5' → 3' exonuclease activity |
| D. | partially 5' → 3' endonuclease activity |
| Answer» B. 5' → 3' endonuclease activity | |
| 163. |
In sperm heads, DNA is particularly highly condensed and the histones are replaced with small basic protein called |
| A. | protamines |
| B. | purines |
| C. | pyrimidines |
| D. | all of the above |
| Answer» B. purines | |
| 164. |
Which of the following would not contain DNA? |
| A. | Yeast |
| B. | Bacteria |
| C. | Glass crystals |
| D. | Mold |
| Answer» D. Mold | |
| 165. |
The nucleosome consists of histone |
| A. | octamer and 146 bp of DNA |
| B. | tetramer and 146 bp of DNA |
| C. | hexamer and 146 bp of DNA |
| D. | none of the above |
| Answer» B. tetramer and 146 bp of DNA | |
| 166. |
Enzymes, responsible for unraveling short segments of DNA is |
| A. | DNA polymerase |
| B. | helicase |
| C. | DNA ligase |
| D. | primase |
| Answer» C. DNA ligase | |
| 167. |
Enzyme, responsible for proofreading base pairing is |
| A. | DNA polymerase |
| B. | Telomerase |
| C. | Primase |
| D. | DNA ligase |
| Answer» B. Telomerase | |
| 168. |
What bands will be observed in a cesium chloride gradient after two rounds of replication? |
| A. | One light, one medium and one heavy band |
| B. | One light and one medium band |
| C. | One medium band |
| D. | One medium and one heavy band |
| Answer» C. One medium band | |
| 169. |
Which is the largest among the followings? |
| A. | Nucleotide |
| B. | Nitrogenous base |
| C. | Phosphate |
| D. | Carbon |
| Answer» B. Nitrogenous base | |
| 170. |
The chromosomal DNA complexes with |
| A. | three types of histone as H1, H2A and H4 |
| B. | five types of histone as H1, H2A, H2B, H3 and H4 |
| C. | four types of histone as H1, H2A, H3 and H4 |
| D. | two types of histone as H1 and H4 |
| Answer» C. four types of histone as H1, H2A, H3 and H4 | |
| 171. |
When DNA polymerase is in contact with guanine in the parental strand, what does it add to the growing daughter strand? |
| A. | Phosphate |
| B. | Cytosine |
| C. | Uracil |
| D. | Guanine |
| Answer» C. Uracil | |
| 172. |
Telomeres are usually rich in which nucleotide? |
| A. | Adenine |
| B. | Guanine |
| C. | Thymine |
| D. | Cytosine |
| Answer» C. Thymine | |
| 173. |
The accepted hypothesis for DNA replication is |
| A. | conservative theory |
| B. | dispersive theory |
| C. | semi-conservative theory |
| D. | evolutionary theory |
| Answer» D. evolutionary theory | |
| 174. |
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 | |
| 175. |
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. | |
| 176. |
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 | |
| 177. |
Reverse transcriptase produces |
| A. | DNA from peptides |
| B. | RNA from DNA |
| C. | RNA from RNA |
| D. | DNA from RNA |
| Answer» E. | |
| 178. |
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 | |
| 179. |
Messelsen and Stahl model of replication was called |
| A. | conservative replication |
| B. | semi-conservative replication |
| C. | dispersive replication |
| D. | Cri du Chat |
| Answer» C. dispersive replication | |
| 180. |
The most common liquid volumes in molecular biology are measured in |
| A. | ml |
| B. | μl |
| C. | nl |
| D. | 1 |
| Answer» C. nl | |
| 181. |
In DNA double helix, the two DNA chains are held together by |
| A. | covalent bonds between the pair of bases |
| B. | hydrogen bonds between the pair of bases |
| C. | ionic bonds between the pair of bases |
| D. | none of the above |
| Answer» C. ionic bonds between the pair of bases | |
| 182. |
The 5' and 3' numbers are related to the |
| A. | length of the DNA strand |
| B. | carbon number in sugar |
| C. | the number of phosphates |
| D. | the base pair rule |
| Answer» C. the number of phosphates | |
| 183. |
Taylor, Woods and Hughes labeled Vicia DNA by allowing new DNA synthesis in the presence of radioactive thymine. After DNA replication (S phase of the cell cycle), it was observed that |
| A. | only one chromatid of a chromosome was labeled |
| B. | both chromatids of a chromosome were labeled |
| C. | both (a) and (b) |
| D. | neither chromatid was labeled |
| Answer» C. both (a) and (b) | |
| 184. |
What is the range of melting point temperatures (Tm) for most DNA molecules? |
| A. | 50 to 60°C |
| B. | 60 to 80°C |
| C. | 70 to 90°C |
| D. | 80 to l00°C |
| Answer» E. | |
| 185. |
What is the approximate size (in kb) of the E. coli genome? |
| A. | 3000 kilobase |
| B. | 4500 kilobase |
| C. | 5500 kilobase |
| D. | 6500 kilobase |
| Answer» C. 5500 kilobase | |
| 186. |
In the study of one experiment it was found that the value of Tm for DNA is = 40° C. If the cell has 20% GC at the above Tm, then what will be value of 'Tm' if the GC% increases to 60%? |
| A. | Remains same |
| B. | Increases |
| C. | Decreases |
| D. | Can not be compared |
| Answer» C. Decreases | |
| 187. |
What is the only common methylation in the DNA of eukaryotes? |
| A. | Adenosine in GpA dinucleotides |
| B. | Guanosine in ApGpA trinucleotides |
| C. | Cytosine in CpG dinucleotides |
| D. | None of the above |
| Answer» D. None of the above | |
| 188. |
DNAs when charged, migrate in a gel towards the |
| A. | positive pole |
| B. | negative pole |
| C. | will not migrate |
| D. | none of these |
| Answer» B. negative pole | |
| 189. |
The structure in a bacterium that indicates an active site for protein synthesis is |
| A. | a chromosome. |
| B. | a cell membrane, |
| C. | a flagellum. |
| D. | a polysome. |
| Answer» E. | |
| 190. |
Ribosomes select the correct tRNAs |
| A. | then bind to the appropriate mRNA |
| B. | solely on the basis of their anticodons |
| C. | depending on their abundance in the cytosol |
| D. | with the least abundant anticodons |
| Answer» C. depending on their abundance in the cytosol | |
| 191. |
Amino acids are joined together into a protein chain by which of the following? |
| A. | Transfer RNA |
| B. | DNA polymerase |
| C. | Hydrogen bonds |
| D. | Messenger RNA |
| Answer» B. DNA polymerase | |
| 192. |
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 | |
| 193. |
Signal peptide protein removal that is translocated across a membrane is accomplished by |
| A. | fMet aminopeptidase |
| B. | trypsin |
| C. | signal peptidase |
| D. | chymotrypsin |
| Answer» D. chymotrypsin | |
| 194. |
Replication in E. coli is initiated by the generation of short RNA primers using |
| A. | RNA polymerase |
| B. | primase |
| C. | reverse transcriptase |
| D. | both (a) and (b) |
| Answer» E. | |
| 195. |
DNA replication in eukaryotes occurs only in |
| A. | G1 phase |
| B. | S phase |
| C. | G2 phase |
| D. | M phase |
| Answer» C. G2 phase | |
| 196. |
30 nm wide helix with five or six nucleosomes per helix is known as |
| A. | solenoid |
| B. | halonoid |
| C. | kinoplast |
| D. | none of these |
| Answer» B. halonoid | |
| 197. |
Which of the following inhibits initiation at higher concentrations? |
| A. | Chloramphenicol |
| B. | Streptomycin |
| C. | Diphtheria toxin |
| D. | Ricin |
| Answer» C. Diphtheria toxin | |
| 198. |
Which type of supercoiling takes the form of extended right-handed coils? |
| A. | Plectonemic supercoiling |
| B. | Solenoidal supercoiling |
| C. | Negative supercoiling |
| D. | Positive supercoiling |
| Answer» B. Solenoidal supercoiling | |
| 199. |
Which of the following solves the problem of shortening of chromosomes in each cell cycle? |
| A. | DNA ligase |
| B. | Endonuclease |
| C. | Telomerase |
| D. | RNA polymerase |
| Answer» D. RNA polymerase | |
| 200. |
An alteration in a nucleotide sequence that changes a triplet coding for an amino acid into a termination codon is |
| A. | Nonsense mutation |
| B. | Mutagenesis |
| C. | Mutation |
| D. | Mutagen |
| Answer» B. Mutagenesis | |