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Molecular Basis of Inheritance · Question 161

AIPMT 2001MCQHard📈 Topic in 75% papers+4−1
1

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

Answer

(1) Both strains have different cistrons

Solution

As per NCERT, a cistron is a segment of DNA coding for a polypeptide.

∵ The R-II region of T4 has two cistrons (A and B), each coding for a polypeptide needed to lyse the host.

⇒ If R-IIX is mutated in one cistron and R-IIY in the other, then in a mixed infection each strain supplies the functional polypeptide that the other lacks (complementation test of Benzer).

∴ Together they lyse E. coli, which shows that the two strains have mutations in different cistrons.

Answer: (1)

AIPMT 2001

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2

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
3

Which of the following is initiation codon?

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

Anticodon occurs in:

  1. DNA
  2. r-RNA
  3. t-RNA
  4. m-RNA
AIPMT 2000
5

Length of one loop of B-DNA:

  1. 20 nm.
  2. 10 nm.
  3. 3.4 nm.
  4. 0.34 nm.
AIPMT 2000
6

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

  1. E-shaped
  2. L-shaped
  3. S-shaped
  4. Y-shaped
AIPMT 2000
7

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
8

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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