CBSE Class 12 Biology Molecular Basis of Inheritance MCQs Set 06

Question: Histones are rich in
a) histidine and serine
b) cysteine and tyrosine
c) lysine and arginine
d) alanine and glycine
Answer: c

Question: The two strands of DNA are held together by
a) phosphodiester bonds
b) hydrogen bonds
c) peptide bonds
d) S–S bonds
Answer: b

Question: Who proved that DNA is the basic genetic material?
a) Watson
b) Griffith
c) Boveri and Sutton
d) Hershey and Chase
Answer: d

Question: Chargaff’s rules are applicable to
a) single stranded RNA
b) single stranded DNA
c) single stranded DNA and RNA
d) double stranded DNA
Answer: d

Question: Leading strand during DNA replication is formed
a) in short segments
b) continuously
c) first
d) ahead of replication
Answer: b

Question: Segments of mRNA removed during splicing are called
a) exons
b) introns
c) promoter regions
d) integrator regions
Answer: b

Question: In Streptococcus pneumoniae
a) virulent form is rough
b) non-virulent form is capsulated
c) virulent form is smooth
d) all forms are rough
Answer: c

Question: Initiation codon of protein synthesis (in eukaryotes) is
a) GUA
b) CCA
c) GCA
d) AUG
Answer: d

Question: Nucleosome is
a) satellite DNA
b) intron interrupted DNA
c) double helix DNA
d) negatively charged DNA wrapped around positively charged histone octomer
Answer: d

Question: During infection of E. coli cells by bacteriophage T2
a) both proteins and nucleic acids enter the cell
b) only proteins from infecting phage can be detected in progeny
c) proteins are the only phage components that enter the cell
d) only nucleic acids enter the cell
Answer: d

Question: Methyl guanosine triphosphate is added at 5′ end of hn-RNA in the process of
a) splicing
b) tailing
c) capping
d) none of these
Answer: c

Question: In some viruses, RNA is present instead of DNA indicating that
a) RNA can act to transfer heredity
b) they cannot replicate
c) there is no hereditary information
d) their nucleic acid must combine with host DNA before replication
Answer: a

Question: Lactose operon produces enzymes
a) β-galactosidase, permease and phosphoglucose isomerase
b) permease, glycogen synthetase and transacetylase
c) β-galactosidase, permease and transacetylase
d) β-galactosidase, permease and glycogen synthetase
Answer: c

Question: Satellite DNA
a) normally does not code for any protein
b) shows polymorphism
c) is classified into microsatellites, minisatellites etc.
d) all of the above
Answer: d

Question: Which of the following is correct for Watson and Crick’s model of DNA? It is duplex with
a) 20 base pairs and 34 Å for each turn
b) 10 base pairs and 3.4 Å distance for every turn
c) 10 base pairs and 3.4 Å distance for each turn of spiral
d) none of the above
Answer: a

Question: Polymorphism in DNA sequence
a) arises due to mutation
b) is the basis of DNA fingerprinting
c) is the basis of genetic mapping of human genome
d) all of the above
Answer: d

Question: SNP pronounced as “snips” stands for
a) Small Nuclear Protein
b) Single Nucleotide Particle
c) Small Nicking Points
d) Single Nucleotide Polymorphism
Answer: d

Statement Type Questions

Question: Identify the incorrect statement about RNA.
a) RNA was the first genetic material to evolve in the living systems.
b) Apart from being a genetic material, it is also a catalyst.
c) DNA evolved from RNA with chemical modifications.
d) RNA being a catalyst is non-reactive and stable.
Answer: d

Question: Which of the following statement is correct about DNA polymerase?
a) DNA polymerase can synthesize mRNA in the 3′ to 5′ direction.
b) DNA polymerase can synthesize DNA in the 5′ to 3′ direction.
c) DNA polymerase can synthesize mRNA in the 5′ to 3′ direction.
d) DNA polymerase can synthesize DNA in the 3′ to 5′ direction.
Answer: b

Question: Choose the incorrect statement regarding the observations drawn from the human genome project.
a) Repetitive sequences are stretches of RNA.
b) Less than 2 per cent of the genome codes for protein.
c) SNPs help in tracing human history.
d) Repetitive sequences make up a very large portion of the human genome.
Answer: a

Question: Select the incorrect statement(s).
a) Six codons do not code for any amino acid.
b) Codon is read in mRNA in a contiguous fashion.
c) Three codons function as stop codons.
d) The initiation codon AUG codes for methionine.
Answer: a

Question: Select the correct statement regarding protein synthesis.
a) When the small subunit of the ribosome encounters an mRNA the process of translation begins.
b) Peptidase catalyses the formation of peptide bond.
c) UTRs are present between the start codon and stop codon.
d) At the end of translation, the release factor binds to the initiation codon.
Answer: a

Question: Which of the following statements are correct?
(i) r-RNA provides the template for synthesis of proteins.
(ii) t-RNA brings amino acids and reads the genetic code.
(iii) RNA polymerase binds to promoter and initiates transcription.
(iv) A segment of DNA coding for polypeptide is called intron.
a) (i) and (iii)
b) (i) and (ii)
c) (i), (ii) and (iii)
d) (ii) and (iii)
Answer: d

Question: Select the two correct statements out of the four given below about lac operon.
(i) Six codons do not code for any amino acid.
(ii) Codon is read in mRNA in a contiguous fashion.
(iii) Three codons function as stop codons.
(iv) The initiation codon AUG codes for methionine.
a) (ii) and (iii)
b) (i) and (iii)
c) (ii) and (iv)
d) (i) and (ii)
Answer: c

Critical Thinking Type Questions

Question: DNA replication is semi-conservative as
a) daughter strands are dispersive.
b) both strands of new molecule are synthesized de novo.
c) only non-parent strand acts as template.
d) one of the strand in each new molecule is parental and the other is new.
Answer: d

Question: Which one of the following pair is a purine pair?
a) Cytosine, Thymine
b) Uracil, Guanine
c) Adenine, Thymine
d) Adenine, Guanine
Answer: d

Question: RNA polymerases used for the transcription of genes require a ______ template.
a) rRNA
b) RNA
c) mRNA
d) DNA
Answer: d

Question: During translation, proteins are synthesized by
a) ribosomes using the information on DNA.
b) lysosome using the information on DNA.
c) lysosome using the information on mRNA.
d) ribosome using the information on mRNA.
Answer: d

Question: Operon is a
a) sequence of three nitrogen bases determining a single amino acid.
b) gene responsible for switching on and switching off other genes.
c) segment of DNA specifying a polypeptide.
d) set of closely placed genes regulating a metabolic pathway in prokaryotes.
Answer: d

Question: In terms of DNA and RNA structure, what is a nucleotide?
a) A nucleotide is a heterocyclic base.
b) A nucleotide is a sugar molecule covalently bonded to a heterocyclic base.
c) A nucleotide is a heterocyclic base bonded to phosphate group.
d) A nucleotide is a sugar molecule bonded to phosphate group and a heterocyclic base.
Answer: d

Question: The two strands of a double helix model of DNA are held together by hydrogen bonds between
a) sugar and phosphate groups.
b) sugar and nitrogenous bases.
c) phosphate groups and nitrogenous bases.
d) nitrogenous bases.
Answer: d

Question: Escherichia coli fully labelled with ¹⁵N is allowed to grow in ¹⁴N medium. The two strands of DNA molecule of the first generation bacteria have
a) same density and resemble with their parent DNA.
b) same density but do not resemble with their parent DNA.
c) different density but resemble with their parent DNA.
d) different density and do not resemble with their parent DNA.
Answer: d

Question: What is the main function of tRNA in relation to protein synthesis?
a) Initiates transcription
b) Inhibits protein synthesis
c) Proof reading
d) Identifies amino acids and transport them to ribosomes
Answer: d

Question: During elongation of polypeptide chain, sigma factor is
a) retained for specific function.
b) required during closing of chain.
c) released for re-use.
d) functionless.
Answer: d

Question: Consider the process that a cell uses to replicate its double strand DNA to make copies for daughter cells. Which statement describes the DNA in daughter cells?
a) The two strands of the double helices in both daughter cells consist of segments of new and parental DNA.
b) The double helix in one daughter cell consists of two strands that were originally in the parent cell, while the other consists of two newly made strands.
c) None of the above.
d) The double helices in each daughter cell consists of one parental strand and one newly made strand.
Answer: d

Question: What sequence on the template strand of DNA corresponds to the first amino acid inserted into a protein?
a) UAG
b) AUG
c) UAC
d) TAC
Answer: d

Question: A geneticist isolates a gene for a specific trait and also isolates the corresponding mRNA. The mRNA contains 1,000 fewer bases than the DNA sequence. Did the geneticist isolate the wrong DNA?
a) Yes, the mRNA should contain more bases than the DNA sequence.
b) Yes, mRNA should be the same length as the gene.
c) No, the mRNA was partially degraded.
d) No, the final mRNA contains only exons, the introns were removed.
Answer: d

Question: What effect would you expect if gene expression of the lac operon were completely repressed?
a) Lactose would not be converted into the inducer and the operon could not be induced.
b) Allolactose would accumulate and become toxic.
c) The cell would be more efficient without wasting energy.
d) All of the above.
Answer: c

Question: DNA fingerprinting using Variable Number Tandem Repeats (VNTRs) is based on the observation that
a) VNTR sequences show little variability.
b) every individual has unique alleles at each VNTR locus.
c) the DNA of VNTR loci is more stable than coding regions.
d) VNTR loci are highly polymorphic.
Answer: d

Question: In addition to the human genome sequence, draft or finished genome sequences existed for eight model organisms by 2002. Which of the following organisms is NOT part of that group?
a) Saccharomyces cerevisiae
b) Drosophila melanogaster
c) Oryza sativa
d) Quercus rubra
Answer: d

Assertion / Reason Type Questions

In the following questions, a statement of Assertion is followed by a statement of Reason.
(a) If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion.
(b) If both Assertion and Reason are true but the Reason is not the correct explanation of the Assertion.
(c) If Assertion is true but Reason is false.
(d) If both Assertion and Reason are false.

Question: Assertion : Adenine cannot pair with cytosine
Reason : Adenine and cytosine do not have a perfect match between hydrogen donor and hydrogen acceptor sites. Hence, they cannot pair.
Answer: a

Question: Assertion : The genetic code is degenerate.
Reason : Most amino acids are coded by more than one codon.
Answer: a

Question: Assertion : DNA fingerprinting is very well known for its application in paternity testing is case of disputes.
Reason : It employs the principle of polymorphism in DNA sequences as the polymorphisms are inheritable from parent to children.
Answer: b

Matching Type Questions

Question: Match the following and choose the correct combination from the given options.

     Column – I                        Column – II
A. Splicing                              I. Lac operon
B. Okazaki fragments            II. Lagging strands
C. Jacob and Monad            III. Lactose
D. Inducer                            IV. Removal of intron

(a) A – IV; B – II; C – I; D – III
(b) A – II; B – I; C – IV; D – III
(c) A – IV; B – III; C – I; D – II
(d) A – II; B – III; C – I; D – IV
Answer: a

Question: Match the steps of protein by synthesis given in column-I with their feature given in column-II and select the correct combination from the given options.

      Column – I                    Column – II
A. Termination                  I. Aminoacyl tRNA synthetase
B. Translation                  II. Okazaki fragments
C. Transcription              III. GTP dependent release factor
D. DNA replication          IV. RNA polymerase

(a) A – II; B – I; C – III; D – IV
(b) A – III; B – I; C – IV; D – II
(c) A – IV; B – III; C – I; D – II
(d) A – II; B – III; C – I; D – IV
Answer: b

Question: Match the scientists given in column-I with their work given in column-II and select the correct option.

      Column-I                    Column-II
A. F. Meischer                 I. DNA double helix
B. Griffith                        II. Nuclein
C. Hershey and              III. S. pneumoniae Chase
D. Watson and Crick      IV. Bacteriophages
E. Wilkins and                V. X-ray diffraction studies Franklin

(a) A – II; B – III; C –IV; D – I; E – V
(b) A – V; B – IV; C –III; D – I; E – II
(c) A – I; B – III; C –IV; D – II; E – V
(d) A – I; B – IV; C –III; D – II; E – V
Answer: a

Question: Match column-I (Scientists) with column-II (Discoveries) and select the correct options.

 Column-I                               Column-II   
(Scientists)                           (Discoveries) 
A. Alec Jeffreys                    I. Lac operon
B. F. Sanger                        II. Automated DNA sequences
C. Jacob and Monod            III. DNA finger printing
D. Avery, Mc Leod               IV. Transforming principle and McCarty

(a) A – II; B – III; C – IV; D – I
(b) A – III; B – II; C – I; D – IV
(c) A – III; B – II; C – IV; D – I
(d) A – I; B – II; C – III; D – IV
Answer: b