A DNA fragment of 5000 bp needs to be isolated from E. coli (genome size 4 × 103 kb) genomic library. Q.52 The minimum number of independent recombinant clones required to represent this fragment in a genomic library are: (A) 16 × 102 (B) 12 × 102 (C) 8 × 102 (D) 1.25 × 102

A DNA fragment of 5000 bp needs to be isolated from

E. coli (genome size 4 × 103 kb) genomic library.

Q.52 The minimum number of independent recombinant clones required
to represent this fragment in a genomic library are:

  • (A) 16 × 102
  • (B) 12 × 102
  • (C) 8 × 102
  • (D) 1.25 × 102

Minimum Recombinant Clones for 5000 bp DNA in E. coli Library

Calculating the minimum number of independent recombinant clones ensures a specific DNA fragment appears in a genomic library. This problem involves a 5000 bp fragment from E. coli‘s genome, sized at 4 × 103 kb or 4 × 106 bp.

Correct Answer

(C) 8 × 102

Calculation Method

The basic formula for the minimum clones N is genome size divided by insert size: N = G/f, where G is genome size and f is fragment size. Here, N = 4 × 106/5000 = 800 = 8 × 102. This represents the simplest coverage without probability adjustments.

Option Explanations

(C) 8 × 102: Correct, as 4 × 106 bp/5000 bp = 800 provides representation.
(A) 16 × 102: Equals 1600 clones, possibly from doubling for 99% probability using N = ln(1-P)/ln(1 – f/G), but exceeds the minimum need here.
(B) 12 × 102: Equals 1200 clones, an intermediate value without basis in standard formulas for this setup.
(D) 1.25 × 102: Equals 125 clones, akin to reciprocal calculation but ignores full coverage requirements.

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