CBSE - Molecular Basis of Inheritance Questions and Answers of Class 12 Biology

91 In a DNA strand the nucleotides are linked together by:

1 glycosidic bonds

2 phosphodiester bonds

3 peptide bonds

4 hydrogen bonds

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Answer: phosphodiester bonds

92 A nucleoside differs from a nucleotide. It lacks the:

1 base

2 sugar

3 phosphate group

4 hydroxyl group

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Answer: phosphate group

93 One of the following is true with respect to AUG

1 It codes for methionine only

2 It is also an initiation codon

3 It codes for methionine in both prokaryotes and eukaryotes

4 All of the above

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Answer: All of the above

94 The human chromosome with the highest and least number of genes in them are respectively:

1 Chromosome 21 and Y

2 Chromosome 1 and X

3 Chromosome 1 and Y

4 Chromosome X and Y

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Answer: Chromosome 1 and Y

95 Control of gene expression takes place at the level of:

1 DNA-replication

2 Transcription

3 Translation

4 None of the above

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Answer: Transcription

96 Which was the last human chromosome to be completely sequenced:

1 Chromosome 1

2 Chromosome 11

3 Chromosome 21

4 Chromosome x

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Answer: Chromosome 1

97 23. 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;

1 5′ – A U G A A U G – 3′

2 5′ – U A C U U A C – 3′

3 5′ – C A U U C A U – 3′

4 5′ – G U A A G U A – 3′

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Answer: 5′ – A U G A A U G – 3′

98 The amino acid attaches to the tRNA at its:

1 5′ – end

2 3′ – end

3 Anti codon site

4 DHU loop

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Answer: 3′ – end

99 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?

1 Replace purine with pyrimidines

2 Remove/Replace 2′ OH group with some other group in deoxy ribose

3 Remove/Replace 3′ OH group in deoxy ribose

4 Both ‘2’ and ‘3’

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Answer: Remove/Replace 3′ OH group in deoxy ribose

100 The promoter site and the terminator site for transcription are located at:

1 a. 3′ (downstream) end and 5′ (upstream) end, respectively of the transcription unit

2 5′ (upstream) end and 3′ (downstream) end, respectively of the transcription unit

3 the 5′ (upstream) end

4 the 3′ (downstream) end

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Answer: 5′ (upstream) end and 3′ (downstream) end, respectively of the transcription unit

101 The fact that a purine base always paired through hydrogen bonds with a pyrimidine base leads to, in the DNA double helix:

1 the antiparallel nature

2 the semiconservative nature

3 uniform width throughout DNA

4 uniform length in all DNA

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Answer: uniform width throughout DNA

102 Regulatory proteins are the accessory proteins that interact with RNA polymerase and affect its role in transcription. Which of the following statements is correct about regulatory protein?

1 They only increase expression

2 They only decrease expression

3 They interact with RNA polymerase but do not affect the expression

4 They can act both as activators and as repressors

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