Class 12 Biology MCQs Chapter – 6
41. The human chromosome with highest and least number of genes are
( A ) Chromosome 21 and Y
( B ) Chromosome 1 and X
( C ) Chromosome 1 and Y
( D ) Chromosome X & Y
Answer- ( C )
42. Which of the following phenomena was experimentally proved by Meselson & Stahl ?
( A ) Transformation
( B ) Transduction
( C ) Semi – conservative DNA replication
( D ) central dogma
Answer- ( C )
43. DNA replication takes place at which phase of cell cycle ?
( A ) G1
( B ) S
( C ) G2
( D ) M
Answer- ( B )
44. If a double stranded DNA has 20 % of cytosine , what will be the percentage of adenine in it ?
( A ) 20 %
( B ) 40 %
( C ) 30 %
( D ) 60 %
Answer- ( C )
45. During transcription , the site of DNA molecule at which RNA polymerase binds is called :
( A ) Promoter
( B ) regulator
( C ) receptor
( D ) enhancer
Answer- ( A )
46. Both deoxyribose and ribose belong to a class of sugars called :
( A ) trioses
( B ) hexoses
( C Pentoses
( D ) Polysacharies
Answer- ( C )
47. Amino acid acceptor end of tRNA lies at
( A ) 5 ‘ end
( B ) 3’end
( C ) T C loop
( D ) DHU loop
Answer- ( B )
48. During expression of an operon , RNA polymerase binds to :
( A ) Structural gerte
( B ) regulator gene
( C ) Operator
( D ) Promoter
Answer- ( D )
49. If the sequence of bases in coding strand of DNA is ATTCGATG , then the sequence of bases in mRNA will be :
( A ) TAAGCTAC
( B ) UAAGCUAC
( C ) ATTCGATG
( D ) AUUCGAUG
Answer- ( D )
50. RNA is the genetic material in
( A ) Prokaryotes
( B ) Eukaryotes
( C ) TMV
( D ) E Coil
Answer- ( C )
51. Khorana was a awarded Nobel Prize for :
( A ) Discovering DNA
( B ) Discovering RNA
( C ) Chemical synthesis of gene
( D ) Discovering DNA polymerase .
Answer- ( C )
52. Nucleosome contains :
( A ) Histone molecules
( B ) Nucleotides
( C ) Nucleoplasmin
( D ) Nuclear pore complex
Answer- ( A )
53. Continuously functional genes are :
( A ) Gene battery
( B ) Luxury genes
( C ) Mild genes
( D ) House keeping genes
Answer- ( D )
54. The ultimate source of variations is :
( A ) natural selection
( B ) sexual reproduction
( C ) mutations
( D ) hormonal actions
Answer- ( C )
55. Purine base of DNA molecule has
( A ) A and C
( B ) C and T
( C ) A and G
( D ) None of these
Answer-( C )
56. Which Nitrogenous base is not present in RNA ?
( A ) Thymine
( B ) Uracil
( C ) Adenine
( D ) Guanine
Answer-( A )
57. which base is present in RNA but absent in DNA ?
( A ) uracil
( B ) Guanine
( c ) Cytosine
( D ) Thymine
Answer-( A )
58. Nallisomie organism will have a genetic complement of :
( A ) 2n – 1
( B ) 2n – 2
( c ) 2n + 1
( D ) 2n + 2
Answer-( B )
59. Nucleic acid are strong acids . The acidity is due to :
( A ) phosphates
( B ) sugar
( C ) nitrogen bases
( D ) H – bonds
Answer-( A )
60. Which of the following is involved in transcription of tRNA , 5Sr RNA and Sn RNA of eukaryotes ?
( A ) RNA polymerase I
( B) RNA polymerase II
( C ) RNA polymerase III
( D ) All of these
Answer-( C )
