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Molecular Basis of Inheritance · Question 158

AIPMT 2001MCQMedium📈 Topic in 88% papers+4−1
1

In Negative operon : -

  1. cAMP has negative effect on lac operon
  2. Co-repressor binds with inducer
  3. Co-repressor binds with repressor
  4. Co-repressor does not bind with repressor

Answer

(3) Co-repressor binds with repressor

Solution

In a negatively controlled operon, the repressor protein switches the operon off by binding to the operator.

In a repressible operon (e.g. tryptophan operon) the repressor made by the regulator gene is inactive by itself.

⇒ The end product (e.g. tryptophan) acts as a co-repressor; it binds with the repressor and makes it active.

⇒ The active repressor–co-repressor complex binds to the operator and stops transcription.

cAMP (with CAP) has a positive effect on the lac operon, so option (1) is wrong.

∴ Co-repressor binds with repressor.

Answer: (3)

AIPMT 2001

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2

Gene and cistron words are sometimes used synonymously because : -

  1. One gene contains one cistron
  2. One cistron contains many genes
  3. One gene contains no cistron
  4. One gene contains many cistrons
AIPMT 2001
3

Types of RNA polymerase required in nucleus for RNA synthesis : -

  1. 2
  2. 3
  3. 1
  4. 4
AIPMT 2001
4

A mutant strain of T4 bacteriophage, R-II, fails to lyse E. coli, but when two strains R-IIX and R-IIY are mixed, they lyse E. coli. What may be the possible reason?

  1. Both strains have different cistrons
  2. Both strains have similar cistrons
  3. It is not mutated
  4. Bacteriophage transforms into wild type
AIPMT 2001
5

Method of DNA replication in which two strands of DNA separate and synthesize new strands

  1. Conservative
  2. Non conservative
  3. Dispersive
  4. Semiconservative
AIPMT 2000
6

Which of the following is initiation codon?

  1. AUC
  2. CCU
  3. UAG
  4. AUG
AIPMT 2000
7

Anticodon occurs in:

  1. DNA
  2. r-RNA
  3. t-RNA
  4. m-RNA
AIPMT 2000
8

Length of one loop of B-DNA:

  1. 20 nm.
  2. 10 nm.
  3. 3.4 nm.
  4. 0.34 nm.
AIPMT 2000
9

In three dimensional view the molecule of t-RNA is:

  1. E-shaped
  2. L-shaped
  3. S-shaped
  4. Y-shaped
AIPMT 2000
10

Similarity in DNA and RNA:

  1. Both have similar sugar
  2. Both are genetic material
  3. Both have similar pyrimidine
  4. Both are polymer of nucleotides
AIPMT 2000
11

Which is the most important factor for continuity of a species from evolutionary point of view?

  1. Formation of gametes
  2. Synthesis of proteins
  3. Replication of genetic material
  4. None of these
AIPMT 2000

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