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Molecular Basis of Inheritance · Question 38

NEET (UG) 2022MCQMedium📈 Topic in 88% papers+4−1
1

In an E. coli strain i gene gets mutated and its product cannot bind the inducer molecule. If growth medium is provided with lactose, what will be the outcome?

  1. Only z gene will get transcribed
  2. z, y, a genes will be transcribed
  3. z, y, a genes will not be translated
  4. RNA polymerase will bind the promoter region

Answer

(3) z, y, a genes will not be translated

Solution

As per NCERT, the i gene codes for the repressor of the lac operon. In the absence of an inducer the repressor binds to the operator and prevents RNA polymerase from transcribing the operon. Lactose (allolactose) acts as the inducer: it binds the repressor and inactivates it, so the operator is set free and RNA polymerase transcribes the z, y and a genes.

Here the mutated repressor cannot bind the inducer ⇒ it stays bound to the operator even when lactose is present.

∴ RNA polymerase cannot transcribe the operon; no lac mRNA is formed ⇒ the z, y and a genes will not be translated (no β-galactosidase, permease or transacetylase is made).

Answer: (3)

NEET (UG) 2022

Keep practising — Molecular Basis of Inheritance

2

Ten E. coli cells with 15N-dsDNA are incubated in medium containing 14N nucleotide. After 60 minutes, how many E. coli cells will have DNA totally free from 15N?

  1. 20 cells
  2. 40 cells
  3. 60 cells
  4. 80 cells
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3

In lac operon, z gene codes for

  1. Transacetylase
  2. β-galactosidase
  3. Permease
  4. Repressor
NEET (UG) 2022 (Phase 2)
4

Given below are two statements In the light of the above statements, choose the correct answer from the options given below:

  1. Statement I is incorrect but Statement II is correct
  2. Both Statement I and Statement II are correct
  3. Both Statement I and Statement II are incorrect
  4. Statement I is correct but Statement II is incorrect
NEET (UG) 2022 (Phase 2)
5

Match List - I with List - II. Choose the correct answer from the options given below

  1. (a) - (iii), (b) - (i), (c) - (iv), (d) - (ii)
  2. (a) - (iii), (b) - (ii), (c) - (i), (d) - (iv)
  3. (a) - (iv), (b) - (iii), (c) - (ii), (d) - (i)
  4. (a) - (iv), (b) - (i), (c) - (iii), (d) - (ii)
NEET (UG) 2022 (Phase 2)
6

Match List-I with List-II: Choose the correct answer from the options given below:

  1. (a)-(i), (b)-(ii), (c)-(iv), (d)-(iii)
  2. (a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)
  3. (a)-(ii), (b)-(iv), (c)-(i), (d)-(iii)
  4. (a)-(ii), (b)-(i), (c)-(iv), (d)-(iii)
NEET (UG) 2022 (Phase 2)
7

If DNA contained sulfur instead of phosphorus and proteins contained phosphorus instead of sulfur, what would have been the outcome of Hershey and Chase experiment?

  1. Radioactive phosphorus in bacterial cells
  2. No radioactive sulfur in bacterial cells
  3. Both radioactive sulfur and phosphorus in bacterial cells
  4. Radioactive sulfur in bacterial cells
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8

Against the codon 5' UAC 3', what would be the sequence of anticodon on tRNA?

  1. 5' GUA 3'
  2. 5' AUG 3'
  3. 5' ATG 3'
  4. 5' GTA 3'
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9

If A and C make 30% and 20% of DNA, respectively, what will be the percentage composition of T and G?

  1. T : 20%, G : 20%
  2. T : 20%, G : 30%
  3. T : 30%, G : 20%
  4. T : 30%, G : 30%
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10

Complete the flow chart on central dogma. [figure]

  1. (a) - Transduction; (b) - Translation; (c) - Replication; (d) - Protein
  2. (a) - Replication; (b) - Transcription; (c) - Transduction; (d) - Protein
  3. (a) - Translation; (b) - Replication; (c) - Transcription; (d) - Transduction
  4. (a) - Replication; (b) - Transcription; (c) - Translation; (d) - Protein
NEET (UG) 2021
11

What is the role of RNA polymerase III in the process of transcription in eukaryotes?

  1. Transcribes only snRNAs
  2. Transcribes rRNAs (28S, 18S and 5.8S)
  3. Transcribes tRNA, 5S rRNA and snRNA
  4. Transcribes precursor of mRNA
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