Few sample questions for CET in MOLECULAR BIOLOGY

DNA:
1.In Griffith’s experiment with Pneumococcus and mice,
(1) living non – virulent bacteria transformed the living virulent strains
(2) living non – virulent bacteria transformed the heat killed virulent strains
(3) living virulent bacteria transformed heat killed non- virulent strains
(4) heat killed virulent bacteria transformed living non – virulent strains
2.Purines and pyrimidines donot contain
(1) carbon
(2) nitrogen
(3) phosphorous
(4) oxygen
3.Purines are
(1) large sized, dicyclic, heterocyclic nitrobases
(2) large sized, monocyclic, heterocyclic nitrobases
(3) small sized, monocyclic, heterocyclic nitrobases
(4) small sized, dicyclic, heterocyclic nitrobases
4.In a nucleotide, the nitrogenous base and phosphate group are attached to the
(1) 1’ and 3’ carbon atoms of sugar respectively
(2) 2’ and 3’ carbon atoms of sugar respectively
(3) 1’ and 5’ carbon atoms of sugar respectively
(4) 2’ and 5’ carbon atoms of sugar respectively
5.Guanosine differs from Guanylic acid in not having
(1) phosphate
(2) sugar
(3) nitro-base
(4) phosphate and sugar
6.The lengths of major groove and minor groove are
(1) 22 Å and 12 Å respectively
(2) 20 Å and 10 Å respectively
(3) 34 Å and 3.4 Å respectively
(4) 20 Å and 12 Å respectively
7.Which of the following is not relevant to the structure of double helical DNA ?
(1) the helix makes one complete spiral turn every 34 Ǻ
(2) the distance between adjacent nucleotides is 3.4 Ǻ
(3) each strand of helix has a backbone of alternating ribose sugar and nitrobase
(4) the two adjacent sugar molecules are joined with phosphate by phosphodiester bond
8.The two strands of DNA are held together by H - bonds between
(1) nitrogen bases
(2) phosphoric acid
(3) sugar and phosphate
(4) nitrobases and sugar
9.Identify the incorrect statement;
(1) the two strands of DNA are antiparallel because of phosphodiester bonds
(2) the two strands of DNA coil helically around a common axis
(3) the distance between two base pairs in B-DNA is 34 Ǻ
(4) the diameter of DNA molecule is 20 Ǻ
10.Read the two statements A and B. Choose the correct answer from those given.
Statement A: B-DNA is a right handed helical molecule which is like a twisted ladder.
Statement B: Sugar and phosphate molecules make up the uprights of the ladder and hydrogen bonded bases make up the rungs.
(1) statement A is correct, B is wrong
(2) statement B is correct, A is wrong
(3) both the statements A and B are correct
(4) both the statements A and B are wrong
11.Which of the following statements does not apply to the Watson – Crick model for DNA ?
(1) the two strands of the helix are antiparallel
(2) the double ringed purines of one strand pair with the single ringed pyrimidines of the other strand
(3) the two strands of the helix are held together by covalent bonds
(4) the verticals of the helix are composed of alternately arranged sugar and phosphate units
12.Statement A: A DNA duplex has a constant diameter of 20 À.
Statement B: Dicyclic purines of one strand always pair with monocyclic pyrimidines of the other strand in a DNA molecule.
(1) Both the statements A and B are correct and A is the reason for B
(2) Both the statements A and B are correct and B is the reason for A
(3) Statement A is correct and statement B is wrong
(4) Statement A is wrong and statement B is correct
13.When the base composition of DNA from a bacterium was analysed, 22% of the bases were found to be Adenine. What is the G + C content ?
(1) 44%
(2) 33%
(3) 56%
(4) 22%
14.A sample of DNA is found to have the base composition (mole ratio) of A = 35, T = 25, G = 24 and C = 16. It suggests that
(1) DNA is circular duplex
(2) DNA is linear duplex
(3) DNA is single stranded
(4) it is Z - DNA
15.Identify the correct statement;
(1) DNA is always a right handed helix
(2) mitochondrial DNA is left handed double helix
(3) according to Chargaff’s rule, A + G = T + C
(4) DNA is double stranded in all organisms
16.Z - DNA is
(1) right handed helix with 9 base pairs per turn
(2) right handed helix with 10 base pairs per turn
(3) left handed helix with 11 base pairs per turn
(4) left handed helix with 12 base pairs per turn
17.A DNA strand is directly involved in the synthesis of all the following except a
(1) polypeptide chain
(2) mRNA strand
(3) rRNA strand
(4) complementary DNA strand
18.DNA replication occurs
(1) whenever a cell makes protein
(2) before a cell divides
(3) whenever a cell needs RNA
(4) in the cytoplasm of an eukaryotic cell
19.Which of the following processes occurs in an eukaryotic cell ?
(1) DNA replication only
(2) translation only
(3) DNA replication and translation
(4) DNA replication, translation and transcription
20.The enzymes responsible for unwinding of DNA helix during replication is / are
(1) helicases
(2) topoisomerases
(3) DNA polymerase
(4) primase
21.The enzyme DNA polymerase can add nucleotide to the ________ of sugar of another nucleotide.
(1) 3’ carbon position
(2) 5’ carbon position
(3) 4’ carbon position
(4) both 3’ and 5’ carbon positions
22.Okazaki fragments are small pieces of DNA that are produced at the time of the formation of
(1) leading strand
(2) lagging strand
(3) sense strand
(4) antisense strand
23.Statement A: RNA primers are synthesized using both DNA strands as templates during DNA replication.
Statement B: DNA polymerases do not initiate replication but only elongate DNA from an available –OH group at its 3’ end.
(1) Both the statements A and B are correct and A is the reason for B
(2) Both the statements A and B are correct and B is the reason for A
(3) Statement A is correct and statement B is wrong
(4) Statement A is wrong and statement B is correct
24.DNA having labelled thymidine is allowed to replicate in a medium having non-radioactive thymidine. After three duplications, the number of DNA molecules having labelled thymidine shall be
(1) one
(2) two
(3) four
(4) eight
25.In a bacterial cell, in the absence of ligase enzyme
(1) the accumulation of Okazaki fragments occurs
(2) the RNA primer is not synthesised
(3) replicatioin is not at all initiated
(4) replication becomes continuous
26.In vitro synthesis of RNA and DNA was carried out respectively first by
(1) Kornberg and Nirenberg
(2) Ochoa and Kornberg
(3) Ochoa and Nirenberg
(4) Nirenberg and Khorana
27.DNA ligase was discovered by
(1) H G Khorana
(2) Okazaki
(3) Kornberg
(4) Nirenberg
28.DNA replication requires
(1) helicase, gyrase, DNA polymerase, primase
(2) helicase, RNA primer, ligase, DNA polymerase
(3) RNA primer, DNA polymerase, helicase, ligase, primase
(4) RNA primer, DNA polymerase, primase, helicase, ligase, gyrase
RNA:
29.Ribose sugar is covalently linked to uracil in RNA by
(1) hydrogen bond
(2) amide linkage
(3) phosphodiester bond
(4) disulphide bond
30.RNA and DNA are similar in that they
(1) are double stranded
(2) are polynucleotide chains
(3) have similar pentose sugars
(4) have similar pyrimidines
31.Which nitrogenous base is normally used in the synthesis of ribonucleic acid but not in the synthesis of deoxyribonucleic acid ?
(1) guanine
(2) cytosine
(3) uracil
(4) thymine
32.Which of the following has the highest molecular weight ?
(1) Mrna
(2) rRNA
(3) tRNA
(4) snRNA
33.The prokaryotic mRNA has
(1) poly A tail at 5’ end
(2) poly A tail at 3’ end
(3) poly A tail at both the ends
(4) no poly A tail
34.After the mRNA molecule is transcribed from an eukaryotic gene, segments called _______ are removed and the remaining ________ are spliced together to produce a mRNA molecule with a continuous coding sequence.
(1) exons ………….. introns
(2) exons ……………. promoters
(3) introns ………… exons
(4) introns …………... regulators
35.What is not true about RNA ?
(1) It has an important role in protein synthesis
(2) mRNA is the most abundant of all RNA in the cell
(3) tRNA selects amino acids as per codon for peptide assembly
(4) There are atleast 20 types of tRNA
36.Which is true about RNA ?
(1) tRNA acts as adapter for transferring amino acids to mRNA template during protein synthsis
(2) rRNA is the smallest RNA
(3) rRNA directs the sequence of amino acids in a polypeptide
(4) RNA has higher molecular weight than DNA
37.In the synthesis of proteins, what is the function of mRNA molecules ?
(1) to act as a template for the synthesis of deoxyribonucleic acid
(2) to carry information that determines the sequence of amino acids
(3) to carry the anticodons and amino acids to the ribosomes
(4) to carry specific enzymes for the formation of peptide bonds between amino acids
38.This virus has double stranded genomic RNA
(1) TMV
(2) wound tumor virus
(3) HIV
(4) HBV
39.DHU loop in tRNA is
(1) amino acid binding site
(2) ribosomal binding site
(3) amino-acyl binding site
(4) mRNA binding site
40.The greek letter  in in the TC loop of tRNA molecule denotes
(1) pseudouridine
(2) dihydrouridine
(3) inosine
(4) ribothymidine
41.The 5’ end of a tRNA always starts with and 3’ end terminates with
(1) A and GGA respectively
(2) G and CCA respectively
(3) GGA and G respectively
(4) A and CAC respectively
42.NODOC is
(1) a unit of three nucleotides on tRNA
(2) a unit of three nucleotides on mRNA
(3) amino acid binding site in the ribosome
(4) the initiation factor required for protein synthesis
43.tRNA molecule does not have one of the following;
(1) anticodon
(2) amino acid binding site
(3) aminoacyl synthetase site
(4) ATP site
44.A RNA polymerase among the following is
(1) reverse transcriptase
(2) primase
(3) RNAase
(4) topoisomerase
45.RNA directed DNA synthesis was first reported in
(1) polio virus
(2) rhabdovirus
(3) retrovirus
(4) TMV
GENE CONCEPT
46.`One gene-one enzyme’ concept was first proposed by
(1) Beadle & Tatum
(2) Morgan & Sutton
(3) Jacob & Monad
(4) Mendel
47.A gene composed of coding part of exons and non – coding part of introns is called
(1) split gene
(2) clustered gene
(3) multiple gene
(4) cistron
48.The functional unit of a gene which directs the synthesis of a polypeptide chain during protein synthesis is called
(1) replicon
(2) recon
(3) muton
(4) cistron
49.This part of the gene has the maximum number of nucleotides
(1) cistron
(2) recon
(3) replicon
(4) muton
50.The portion of gene which is transcribed but not translated is
(1) cistron
(2) exon
(3) intron
(4) meson
51.Prokaryotic genes are different from eukaryotic genes in that
(1) they produce mono-cistronic mRNA
(2) they produce poly-cistronic mRNA
(3) they are split genes
(4) they are recognised & activated by transcription factors
GENETIC CODE:
52.The stop signals contain the following bases
(1) uracil, guanine and adenine
(2) adenine, guanine and cytosine
(3) adenine, cytosine and uracil
(4) uracil, guanine and thymine
53.A triplet codon which is functionally related to UAA and UAG is
(1) AUG
(2) UGA
(3) AUG
(4) UUU
54.Genetic code is degenerate because
(1) a single triplet codon recognises different amino acids
(2) a single amino acid is recognized by different triplet codons
(3) triplet codons undergo degeneration during translation
(4) triplet codons undergo reduction during translation
55.The first triplet codon to be deciphered by Nirenberg and Matthaei was
(1) UUU
(2) AAA
(3) CCC
(4) AUG
56.Wobble hypothesis establishes
(1) peptide chain formation
(2) initiation of peptide chain
(3) termination of peptide chain
(4) economy of tRNA molecules
57.A messenger RNA molecule for making a protein is made in the nucleus and sent out to a ribosome. The ribosome reads the mRNA message and makes a protein containing 120 amino acids. The mRNA consisted of atleast how many codons ?
(1) 40
(2) 120
(3) 240
(4) 360
PROTEIN SYNTHESIS:
58.All of the following are accurate regarding the processes of transcription and translation except
(1) transcription and translation take place outside the nucleus
(2) transcription and translation are the processes for making enzymes
(3) transcription and translation are the processes for making proteins
(4) transcription and translation occur when a cell is doing its regular cell work
59.The translation machinery consists of
(1) ribosomes and mRNA
(2) ribosomes, mRNA and tRNA
(3) ribosomes, mRNA, tRNA and amino acids
(4) robosomes, mRNA, tRNA, amino acids and amino-acyl tRNA synthetase
60.Central dogma of molecular biology has been modified after the discovery of
(1) reverse transcriptase
(2) DNA polymerase
(3) RNA polymerase
(4) Restriction endonuclease
61.Pick the wrong statement with respect to protein synthesis in eukaryotes
(1) during initiation, methionine is formylated
(2) synthesis occurs in 80 S ribosomes
(3) translation begins after the completion of transcription
(4) usually monoribosomes are employed for synthesis
62.The sequence of nitrogen bases in a portion of the sense strand of DNA was AAT GCT TAG GCA. What will be the sequence of nitrogen bases in the corresponding region of the transcripted mRNA ?
(1) UUT CGT TUC CGU
(2) AAU GCU UAG GCA
(3) UUA CGA AUC CGU
(4) TTA CGA ATC CGT
63.Choose the answer that has the following events of protein synthesis in the proper sequence;
(a) large sub-unit of ribosome gets attached to small sub-unit to form a complex
(b) a charged tRNA with the anticodon UAC binds to AUG of mRNA at P site of ribosome
(c) a second tRNA with an amino acid occupies the A site
(d) small ribosomal sub-unit associates with mRNA
(e) peptidyl transferase catalyses the formation of peptide bond
(1) a, c, b, d, e
(2) b, d, e, a, c
(3) d, b, a, c, e
(4) d, a, c, b, e
OPERON CONCEPT:
64.In E.coli, gene action is regulated
(1) at the time of transcription
(2) at the time of translation
(3) after transcription
(4) after translation
65.Wild type of E.coli cells are growing in normal medium with glucose. They are transferred to a medium containing only lactose as the sugar. Which one of the following changes takes place ?
(1) the lac – operon is repressed
(2) all operons are induced
(3) E.coli cells stop dividing
(4) the lac – operon is induced
66.In Lac – operon, the structural gene ‘z’ is responsible for the synthesis of the enzyme
(1) β – galactosidase
(2) galactoside permease
(3) galactoside transacetylase
(4) lactase
67.During transcription by a cistron, the DNA site at which RNA polymerase binds/interacts is
(1) promoter
(2) regulator
(3) operator
(4) repressor
68.According to operon concept, the regulatory gene regulates biochemical reactions in a cell by
(1) inhibiting transcription
(2) inactivating the enzymes
(3) inactivating the substrates
(4) inhibiting the migration of mRNA
69.The recognition site in the promoter region of a Lac - operon is sometimes referred to as
(1) TATA (TATAA box)
(2) Pribnow box
(3) Hognesse box
(4) poly A tail
70.Match the components of Lac operon of E. coli and choose the correct combination
Column I Column II
A. Structural gene p. Binding site for
repressor protein
B. Operator gene q. Codes for repressor
protein
C. Promoter gene r. Induces lactose transport
from the medium
D. Regulator gene s. Codes for enzyme proteins
t. Binding site of RNA
polymerase
(1) A = q, B = t, C = p, D = r
(2) A = r, B = s, C = t, D = p
(3) A = s, B = p, C = t, D = q
(4) A = t, B = s, C = q, D = p

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