Molecular Biology- Multiple-choice questions (set-1)

Q.1- A critical enzyme used directly in the synthesis of dTMP (thymidine) is

a) Carbamoyl phosphate

b) Aspartate Transcarbamylase

c) Dihydrooratase

d) Thymidylate synthase

Q.2- In which phase of the cell cycle does DNA replication occur?

a) G₀

b) G₁

c) S

d) G₂

Q.3-A 10-month-old baby boy presents with steatorrhea, recurrent pulmonary infections, GI upset, and foul-smelling stool. Which of the following tests is undertaken to confirm your diagnosis?

a) Sweat test

b) Blood glucose

c) CBC

d) RFLP analysis

Q.4-The enzyme responsible for initiating DNA replication in prokaryotes is:

a) DNA polymerase I

b) DNA polymerase III

c) Polymerase beta

d) Primase

Q.5- The enzyme responsible for continuing DNA replication in prokaryotes, once it is initiated, is:

a) DNA polymerase I

b) DNA polymerase III

c) polymerase beta

d) polymerase delta

Q.6- Antibiotics such as Ciprofloxacin and Fluoroquinolones work by inhibiting a specific enzyme. This enzyme is normally necessary to relieve the torsional strain caused by the unwinding of the helix. What is the name of this enzyme?

a) DNA ligase

b) Topoisomerase (DNA Gyrase)

c) single-stranded binding protein

d) primase

Q.7- Which of the following techniques is primarily undertaken to amplify DNA?

a) PCR

b) Microarrays

c) Northern Blotting

d) Southern Blotting

Q.8- In Pyrimidine synthesis, eukaryotes can use uracil to feedback inhibit which of the following enzymes?

a) Carbamoyl phosphate synthase

b) Aspartate transcarbamoylase

c) Dihydrooratase

d) Thymidylate synthase

Q.9- All of the following are required for the purine de novo synthesis EXCEPT:

a) CO2

b) Glycine

c) Glutamine

d) Isoleucine

Q.10- Which of the following, in high concentrations, can overcome inhibition of de novo purine nucleotide biosynthesis?

a) Ribose-5-phosphate

b) PRPP

c) 5-phosphoribosyl 1-amine

d) GDP

Q.11- A 40-year-old alcoholic comes in with severe pain in his big toe.  You decide to administer Allopurinol to inhibit which of the following enzymes?

a) Xanthine Oxidase

b) Thymidine kinase

c) Adenosine Deaminase

d) Adenine phosphoribosyltransferase

Q.12- All of the following are used in PCR EXCEPT:

a) Taq polymerase

b) Restriction enzymes

c) Oligonucleotide primers

d) Deoxynucleoside triphosphates

Q.13- The following are features of DNA replication EXCEPT:

a) Semi-conservative

b) Semi-discontinuous

c) unidirectional

d) chain growth in the 5’ –> 3’ direction

Q.14- The oncogene Ras binds:

a) ATP

b) GTP

c) Glucose

d) Hemoglobin

Q.15- Which of the following mechanisms is involved in the production of a variety of immunoglobulins, each specific for a specific antigen?

a) Class switching

b) Gene amplification

c) Gene rearrangement

d) RNA editing

Q. 16- Which of the following is a common enzyme for de novo as well as the salvage pathway of purine biosynthesis?

a) Amidotransferase

b) PRPP synthetase

c) HGPRTase

d) Adenylosuccinate synthetase

Q. 17- Which of the following does not have introns?

a) DNA

b) Non-processed pseudogenes

c) Processed m RNA

d) Primary RNA transcript

Q.18- Which of the following is NOT true of RNA synthesis?

a)  The key enzyme is RNA polymerase

b)  The energy is supplied by ring cleavage

c) The RNA sequence is complementary to the template strand of DNA

d) The RNA sequence is of opposite polarity to the template strand of DNA

Q.19-  If the molar amount of G in a DNA sample is 20%, what is the molar amount of T in the sample?

a) 20%

b) 30%

c) 40%

d) 60%

Q.20- With respect to the lac operon, if both glucose and lactose are present and glucose is low, which of the following is NOT true?

a) High CAP

b) increased uptake of lactose

c) low cAMP

d) increased transcription of the lac operon

Q.21- Which of the following subunits of the bacterial RNA polymerase is responsible for promoter recognition?

a) alpha

b) B

c) B’

d) sigma

Q. 22- What is true of the melting temperature of G-C pairs compared to A-T pairs in DNA?

a)The Tm is equal

b) Tm of G-C is less than the Tm of A-T

c) Tm of G-C is greater than the Tm of A-T

d) None of the above.

Q.23- A 10-year-old boy comes to the ER after eating wild mushrooms.  The poison associated with these mushrooms most likely DIRECTLY inhibits the synthesis of the following:

a) hn RNA

b) t RNA

c) DNA

d) m RNA

Q.24- DNA methylation is associated with:

a) CpG islands

b) CAT box

c) TATA box

d) increasing gene transcription

Q.25-Alternative splicing…

a) Creates protein from multiple segments of DNA on different chromosomes

b) Is the reason why the human genome is much more complex than other species

c) Creates different proteins from a single gene

d) is not tissue-specific.

Q.26-All of the following are involved in translating information into proteins EXCEPT:

a) rRNA

b) siRNA

c) tRNA

d) snRNA

Q. 27- Which histone is NOT part of the nucleosome?

a) H1

b) H2A

c) H2B

d) H3

Q. 28- Which of the following is an inhibitor of prokaryotic transcription?

a) Ciprofloxacin

b) Etoposide

c) Erythromycin

d) Rifampicin

Q.29- Choose the nucleoside analog used as an anticancer drug out of the following

a) Methotrexate

b) 6- Mercaptopurine

c) Vinblastin

d) Cytosine Arabinoside

Q.30- Which amino acid residue is in abundance in histones?

a) Arginine

b) Aspartic acid

c) Tryptophan

d) Phenylalanine

Q.31-Which out of the following techniques is used for the detection of the gene of interest –

a) Southern Blotting

b) Polymerase chain reaction

c) Northern Blotting

d) DNA Footprinting

Q. 32- Which of the following is an example of post-translational modification?

a) Splicing

b) Class switching

c) Subunit aggregation

d) Base modification

Q.33- Which of the following is a substrate required for purine biosynthesis?

a) 5- methyl thymidine

b) Ribose phosphate

c) Ara C

d) PRPP (5- phosphoribosylpyrophosphate)

Q.34-Triple repeat sequence disease occurs in:

a)Alzheimer’s disease

b) Cystic fibrosis

c) Ataxia telangiectasia

d) Huntington’s chorea

Q.35-Northern blotting is used in the separation of:

a) DNA

b) mRNA

c) Protein

d) Protein DNA interactions

Key to Answers-

1-d,       

2-c,        

3-d,       

4-d,       

5-b,       

6-b,       

7-a,       

8-a,       

9-d,       

10-b,     

11-a,     

12-b,     

13-c,

14-b,     

15-c,     

16-b,     

17-c,     

18-b,     

19-b,     

20-c,     

21-d,     

22-c,     

23-a,     

24-a,     

25-c,     

26-b,

27-a,     

28-d,     

29-d,     

30-a,     

31-a,     

32-c,     

33-d,     

34-d,     

35-b

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