#6 Biology Class XII- Molecular Basis of Inheritance (NEET, MHTCET) MCQ
1) Amino acid sequence, in protein synthesis is decided by the sequence of
(a) rRNA
(b) tRNA
(c) mRNA
(d) cDNA
Answer
(c) mRNA
2) Antiparallel strands of a DNA molecule means that
(a) one strand turns clockwise
(b) one strand turns anti-clockwise
(c) the phosphate groups of two DNA strands, at their ends, share the same position
(d) the phosphate groups at the start of two DNA strands are in opposite position (pole).
Answer
(d) the phosphate groups at the start of two DNA strands are in opposite position (pole).
3) Polysome is formed by
(a) a ribosome with several subunits
(b) ribosomes attached to each other in a linear arrangement
(c) several ribosomes attached to a single mRNA
(d) many ribosomes attached to a strand of endoplasmic reticulum.
Answer
(c) several ribosomes attached to a single mRNA
4) In the DNA molecule
(a) the proportion of adenine in relation to thymine varies with the organism
(b) there are two strands which run antiparallel—one in direction and other in
(c) the total amount of purine nucleotides and pyrimidine nucleotides is not always equal
(d) there are two strands which run parallel in the direction.
Answer
(b) there are two strands which run antiparallel—one in direction and other in
5) What is not true for genetic code?
(a) It is nearly universal.
(b) It is degenerate.
(c) It is unambiguous
(d) A codon in mRNAt is read in a non-contiguous fashion.
Answer
(d) A codon in mRNAt is read in a non-contiguous fashion.
6) Removal of introns and joining the exons in a defined order in a transcription unit is called
(a) tailing
(b) transformation
(c) capping
(d) splicing
Answer
(d) splicing
7) The fact that a purine base always pairs through hydrogen bonds with a pyrimidine base in the DNA double helix leads to [NCERT Exemplar]
(a) the antiparallel nature
(b) the semiconservative nature
(c) uniform width throughout DNA
(d) uniform length in all DNA
Answer
(c) uniform width throughout DNA
8) The net electric charge on DNA and histones is [NCERT Exemplar]
(a) both positive
(b) both negative
(c) negative and positive, respectivel
(d) zero
Answer
(c) negative and positive, respectivel
9) Gene controls
(a) protein synthesis but not heredity
(b) protein synthesis and heredity
(c) heredity but not protein synthesis
(d) biochemical reaction of some enzymes
Answer
(b) protein synthesis and heredity
10) The promoter site and the terminator site for transcription are located at [NCERT Exemplar]
(a) 3’ (downstream) end and 5’ (upstream) end, respectively of the transcription unit
(b) 5’ (upstream) end and 3’ (downstream) end, respectively of the transcription unit
(c) the 5’ (upstream) end
(d) the 3’ (downstream) end
Answer
(b) 5’ (upstream) end and 3’ (downstream) end, respectively of the transcription unit
11) Which of the following statements is the most appropriate for sickle cell anaemia? [NCERT Exemplar]
(a) It cannot be treated with iron supplements
(b) It is a molecular disease
(c) It confers resistance to acquiring malaria
(d) All of the above
Answer
(d) All of the above
12) With regard to mature mRNA in eukaryotes [NCERT Exemplar]
(a) exons and introns do not appear in the mature RNA
(b) exons appear but introns do not appear in the mature RNA
(c) introns appear but exons do not appear in the mature RNA
(d) both exons and introns appear in the mature RNA
Answer
(d) both exons and introns appear in the mature RNA
13) The human chromosome with the highest and least number of genes in them are respectively
[NCERT Exemplar]
(a) Chromosome 21 and Y
(b) Chromosome 1 and X
(c) Chromosome 1 and Y
(d) Chromosome X and Y
Answer
(c) Chromosome 1 and Y
14) Who amongst the following scientists had no contribution in the development of the double helix model for the structure of DNA? [NCERT Exemplar]
(a) Rosalind Franklin
(b) Maurice Wilkins
(c) Erwin Chargaff
(d) Meselson and Stahl
Answer
(d) Meselson and Stahl
15) DNA is a polymer of nucleotides which are linked to each other by 3’-5’ phosphodiester bond. To prevent polymerisation of nucleotides, which of the following modifications would you choose? [NCERT Exemplar]
(a) Replace purine with pyrimidines
(b) Remove/replace 3’ OH group in deoxy ribose
(c) Remove/replace 2’ OH group with some other group in deoxy ribose
(d) Both ‘b’ and ‘c’
Answer
(d) Both ‘b’ and ‘c’
16) Discontinuous synthesis of DNA occurs in one strand, because [NCERT Exemplar]
(a) DNA molecule being synthesised is very long
(b) DNA dependent DNA polymerase catalyses polymerisation only in one direction (5’ 3’)
(c) it is a more efficient process
(d) DNA ligase joins the short stretches of DNA
Answer
(b) DNA dependent DNA polymerase catalyses polymerisation only in one direction (5’ 3’)
17) Which of the following steps in transcription is catalysed by RNA polymerase?
[NCERT Exemplar]
(a) Initiation
(b) Elongation
(c) Termination
(d) All of the above
Answer
(b) Elongation
18) Control of gene expression in prokaryotes take place at the level of [NCERT Exemplar]
(a) DNA-replication
(b) Transcription
(c) Translation
(d) None of the above
Answer
(b) Transcription
19) Which of the following statements is correct about the role of regulatory proteins in transcription in prokaryotes? [NCERT Exemplar]
(a) They only increase expression
(b) They only decrease expression
(c) They interact with RNA polymerase but do not affect the expression
(d) They can act both as activators and as repressors
Answer
(d) They can act both as activators and as repressors
20) Which was the last human chromosome to be completely sequenced? [NCERT Exemplar]
(a) Chromosome 1
(b) Chromosome 11
(c) Chromosome 21
(d) Chromosome X
Answer
(a) Chromosome 1
21) Which of the following are the functions of RNA? [NCERT Exemplar]
(a) It is a carrier of genetic information from DNA to ribosomes synthesising polypeptides.
(b) It carries amino acids to ribosomes.
(c) It is a constituent component of ribosomes.
(d) All of the above.
Answer
(d) All of the above.
22) While analysing the DNA of an organism a total number of 5386 nucleotides were found, out of which the proportion of different bases were: Adenine = 29%, Guanine = 17%, Cytosine = 32%, Thymine = 17%.
Considering the Chargaff’s rule it can be concluded that [NCERT Exemplar]
(a) it is a double stranded circular DNA
(b) it is single stranded DNA
(c) it is a double stranded linear DNA
(d) no conclusion can be drawn
Answer
(b) it is single stranded DNA
23) In some viruses, DNA is synthesised by using RNA as template. Such a DNA is called [NCERT Exemplar]
(a) A-DNA
(b) B-DNA
(c) cDNA
(d) rDNA
Answer
(c) cDNA
24) If Meselson and Stahl’s experiment is continued for four generations in bacteria, the ratio of N15/N15: N15/N14: N14/N14 containing DNA in the fourth generation would be
[NCERT Exemplar]
(a) 1:1:0
(b) 1:4:0
(c) 0:1:3
(d) 0:1:7
Answer
(d) 0:1:7
25) If the sequence of nitrogen bases of the coding strand of DNA in a transcription unit is:
5’ - A T G A A T G - 3’, the sequence of bases in its RNA transcript would be [NCERT Exemplar]
(a) 5’ - A U G A A U G - 3’
(b) 5’ - U A C U U A C - 3’
(c) 5’ - C A U U C A U - 3
(d) 5’ - G U A A G U A - 3’
Answer
(a) 5’ - A U G A A U G - 3’
26) In E.coli, the lac operon gets switched on when [NCERT Exemplar]
(a) lactose is present and it binds to the repressor
(b) repressor binds to operator
(c) RNA polymerase binds to the operator
(d) lactose is present and it binds to RNA polymerase
Answer
(a) lactose is present and it binds to the repressor
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