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Molecular Basis of Inheritance · Question 118

AIPMT 2010 (Prelims)MCQMedium📈 Topic in 88% papers+4−1
1

Select the two correct statements out of the four (A–D) statements given below about lac operon. The correct statements are :

  1. B and D
  2. A and B
  3. B and C
  4. A and C

Answer

(1) B and D

Solution

A – Incorrect: as per NCERT, lactose (more precisely its isomer allolactose) acts as the inducer; it binds the repressor and inactivates it. Glucose or galactose cannot act as inducers of the lac operon.

B – Correct: in the absence of an inducer (lactose), the repressor protein binds to the operator region and prevents RNA polymerase from transcribing the operon.

C – Incorrect: the z gene codes for β-galactosidase; permease is coded by the y gene (a codes for transacetylase).

D – Correct: the lac operon was elucidated by François Jacob and Jacques Monod.

∴ B and D are correct.

Answer: (1)

AIPMT 2010 (Prelims)

Keep practising — Molecular Basis of Inheritance

2

Whose experiments cracked the DNA and discovered unequivocally that a genetic code is a "triplet"?

  1. Nirenberg and Matthaei
  2. Morgan and Sturtevant
  3. Hershey and Chase
  4. Beadle and Tatum
AIPMT 2009
3

Semi-conservative replication of DNA was first demonstrated in:

  1. Drosophila melanogaster
  2. Streptococcus pneumoniae
  3. Salmonella typhimurium
  4. Escherichia coli
AIPMT 2009
4

Removal of introns and joining the exons in a defined order in a transcription unit is called:

  1. Transformation
  2. Capping
  3. Splicing
  4. Tailing
AIPMT 2009
5

What is not true for genetic code?

  1. It is nearly universal
  2. A codon in mRNA is read in a noncontiguous fashion
  3. It is degenerate
  4. It is unambiguous
AIPMT 2009
6

In the DNA molecule:

  1. the total amount of purine nucleotides and pyrimidine nucleotides is not always equal
  2. there are two strands which run antiparallel one in 5' 3' direction and other in 3' 5'
  3. there are two strands which run parallel in the 5' 3' direction
  4. the proportion of adenine in relation to thymine varies with the organism
AIPMT 2008
7

Which one of the following pairs of nitrogenous bases of nucleic acids is wrongly matched with the category mentioned against it?

  1. Thymine, Uracil — Pyrimidines
  2. Guanine, Adenine — Purines
  3. Uracil, Cytosine — Pyrimidines
  4. Adenine, Thymine — Purines
AIPMT 2008
8

Which one of the following pairs of codons is correctly matched with their function or the signal for the particular amino acid?

  1. UUA, UCA — Leucine
  2. AUG, ACG — Start/Methionine
  3. UAG, UGA — Stop
  4. GUU, GCU — Alanine
AIPMT 2008
9

One turn of the helix in a B-form DNA is approximately -

  1. 20 nm
  2. 3.4 nm
  3. 2 nm
  4. 0.34 nm
AIPMT 2006
10

One gene-one enzyme hypothesis was postulated by -

  1. A. Garrod
  2. Hershey and Chase
  3. Beadle and Tatum
  4. R. Franklin
AIPMT 2006
11

Antiparallel strands of a DNA molecule means that-

  1. The phosphate groups at the start of two DNA strands are in opposite position (pole)
  2. One strand turns anti-clockwise
  3. One strand turns clockwise
  4. The phosphate groups of two DNA strands, at their ends, share the same position
AIPMT 2006

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