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Molecular Basis of Inheritance · Question 145

AIPMT 2003MCQHard📈 Topic in 38% papers+4−1
1

During translation initiation in prokaryotes, a GTP molecule is needed in:

  1. Association of 30S-mRNA with formyl-met-tRNA
  2. Formation of formyl-met-tRNA
  3. Association of 50S subunit of ribosome with initiation complex
  4. Binding of 30S subunit of ribosome with mRNA

Answer

(1) Association of 30S-mRNA with formyl-met-tRNA

Solution

Initiation of translation in prokaryotes:

(i) The 30S subunit binds the mRNA (with IF-3) — no GTP needed.

(ii) Initiation factor IF-2, bound to GTP, brings the initiator formyl-met-tRNA to the AUG codon of the 30S–mRNA complex, forming the 30S initiation complex — GTP is needed here.

(iii) The 50S subunit then joins, the GTP is hydrolysed and the initiation factors are released.

∴ GTP is required for association of the 30S–mRNA complex with formyl-met-tRNA.

Answer: (1)

AIPMT 2003

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2

Which one of the following triplet codes, is correctly matched with its specificity for an amino acid in protein synthesis or as 'start' or 'stop' codon?

  1. UUU – Stop
  2. UAC – Tyrosine
  3. UGU – Leucine
  4. UCG – Start
AIPMT 2003
3

During transcription, the DNA site at which RNA polymerase binds is called:

  1. Receptor
  2. Regulator
  3. Enhancer
  4. Promoter
AIPMT 2003
4

Degeneracy of a genetic code is attributed to the:

  1. Second member of a codon
  2. Third member of a codon
  3. First member of a codon
  4. Entire codon
AIPMT 2003
5

In the genetic code dictionary, how many codons are used to code for all the 20 amino acids:

  1. 64
  2. 20
  3. 60
  4. 61
AIPMT 2003
6

In a DNA percentage of thymine is 20% then what is the percentage of guanine : -

  1. 40%
  2. 20%
  3. 30%
  4. 60%
AIPMT 2002
7

Transformation experiment was first performed on which bacterium : -

  1. Diplococcus pneumoniae
  2. Pasteurella pestis
  3. E. coli
  4. Salmonella
AIPMT 2002
8

Jacob and Monod studied lactose metabolism in E. coli and proposed operon concept. Operon concept is applicable for :

  1. All prokaryotes and all eukaryotes
  2. All prokaryotes and some protozoans
  3. All prokaryotes
  4. All prokaryotes and some eukaryotes
AIPMT 2002
9

In E. coli, during lactose metabolism repressor binds to : -

  1. Promoter gene
  2. Operator gene
  3. Structural gene
  4. Regulator gene
AIPMT 2002
10

Out of 64 codons, 61 codons code for 20 types of amino acids; it is called : -

  1. Wobbling of codon
  2. Universality of codons
  3. Overlapping of gene
  4. Degeneracy of genetic code
AIPMT 2002
11

Which of the following reunites the exon segments after RNA splicing ?

  1. RNA polymerase
  2. RNA proteases
  3. RNA primase
  4. RNA ligase
AIPMT 2002

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