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Molecular Basis of Inheritance · Question 119

AIPMT 2009MCQMedium📈 Topic in 25% papers+4−1
1

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

Answer

(1) Nirenberg and Matthaei

Solution

As per NCERT, Marshall Nirenberg's cell-free system for protein synthesis (with Heinrich Matthaei) and Severo Ochoa's enzyme (polynucleotide phosphorylase) helped in polymerising RNA of defined sequences, which finally deciphered the code.

⇒ Poly-U RNA gave polyphenylalanine, and such experiments with synthetic RNAs established that a codon is a triplet of bases.

Morgan and Sturtevant – linkage and gene mapping; Hershey and Chase – DNA is the genetic material; Beadle and Tatum – one gene–one enzyme.

Answer: (1)

AIPMT 2009

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2

Semi-conservative replication of DNA was first demonstrated in:

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

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
4

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
5

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
6

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
7

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
8

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
9

One gene-one enzyme hypothesis was postulated by -

  1. A. Garrod
  2. Hershey and Chase
  3. Beadle and Tatum
  4. R. Franklin
AIPMT 2006
10

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
11

Which antibiotic inhibits interaction between tRNA and mRNA during bacterial protein synthesis?

  1. Neomycin
  2. Erythromycin
  3. Tetracycline
  4. Streptomycin
AIPMT 2006

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