NCERT Class 12 Biology: Chapter – 6 Molecular Basis of Inheritance Part 2 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Question 10:

With regard to mature mRNA in eukaryotes:

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: (b)

Question 11:

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

a. Chromosome 21 and Y

b. Chromosome 1 and X

c. Chromosome 1 and Y

d. Chromosome X and Y

Answer: (c)

Question 12:

Who amongst the following scientists had no contribution in the development of the double helix model for the structure of DNA?

a. Rosalind Franklin

b. Maurice Wilkins

c. Erwin Chargaff

d. Meselson and Stahl

Answer: (d)

Question 13:

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?

a. Replace purine with pyrimidines

b. Remove/Replace group in deoxy ribose

c. Remove/Replace group with some other group in deoxy ribose

d. Both ‘B’ and ‘C’

Answer: (b)

Question 14:

Discontinuous synthesis of DNA occurs in one strand, because:

a. DNA molecule being synthesised is very long

b. DNA dependent DNA polymearse catalyses polymerisation only in one direction

c. it is a more efficient process

d. DNA ligase has to have a role

Answer: (b)

Question 15:

Which of the following steps in transcription is catalysed by RNA polymerse?

a. Initiation

b. Elongation

c. Termination

d. All of the above

Answer: (b)

Question 16:

Control of gene expression takes place at the level of:

a. DNA-replication

b. Transcription

c. Translation

d. None of the above

Answer: (b)

Question 17:

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?

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)

Question 18:

Which was the last human chromosome to be completely sequenced:

a. Chromosome 1

b. Chromosome 11

c. Chromosome 21

d. Chromosome x

Answer: (a)