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Considering the cloning process involving gene ‘G’ and vector ‘V’, the student employed specific restriction enzymes (RE). 

Following the gene and vector cuts with RE1 and RE3. In further addition,  the plasmid L is treated with RE2 and exhibited a band of approximately 6.6 kb. 

The following three propositions were put forth to account for this finding that is,

1. Plasmid L is essentially indistinguishable from vector V since solely the uncut V was introduced into E. coli.

2. Gene G has the RE2 recognition site.

3. The restriction enzymes RE1 and RE2 demonstrate iso-schizomeric properties.

Which of the following combinations is correct?

Option: 1

1 only, neither 2 nor 3

Option: 2

2 only, neither 1 nor 3

Option: 3

Either 2 or 3, but not 1 


Option: 4

3 only, neither 1 nor 2

Answers (1)

  • Proposition 1 suggests that plasmid L is the same as vector V because only the uncut V was transformed into E. coli. However, this proposition does not provide any explanation for the observed band size of approximately 6.6 kb.
  • Proposition 2 states that gene G has the recognition site for RE2. This proposition could explain the observed band size, as cutting plasmid L with RE2 would result in a fragment of approximately 6.6 kb if gene G indeed contains the RE2 recognition site.
  • Proposition 3 claims that the restriction enzymes RE1 and RE2 are iso-schizomeric, meaning they recognize the same DNA sequence and produce identical cut patterns. If this proposition is true, cutting plasmid L with RE2, which is an isoschizomer of RE1, would yield a band of approximately 6.6 kb.
  • Based on the given information, the correct combination is option 3, which suggests that either proposition 2 (gene G has the RE2 recognition site) or proposition 3 (RE1 and RE2 are iso-schizomeric) is correct, while proposition 1 is not supported by the given information.
  • Hence, option 3 is the correct answer.
Posted by

Gautam harsolia

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