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Molecular Basis of Inheritance

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

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, and the active repressor–co-repressor complex then 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)

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Ques. 2AIPMT 2001

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
Ques. 3AIPMT 2001

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

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

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
Ques. 5AIPMT 2000

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

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

Which of the following is initiation codon?

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

Anticodon occurs in:

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

Length of one loop of B-DNA:

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

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

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

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
Ques. 11AIPMT 2000

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

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