Question

A DNA sequence of interest was digested and ligated into the middle of the AmpR gene region of pBR322 vector. The vector also contains a TetR gene which is not interrupted. After introducing the recombinat DNA into bacterial cells, the resulting transformants were tested on a variety of media. Which of the following results would be expected?
A) no growth on either ampicillin or tetracycline containing mediaB) growth on ampicillin but not tetracycline containing mediaC) growth on tetracycline but not ampicillin containing mediaD) growth only on media containing both antibioticsE) growth on both ampicillin containing media and tetracycline containing media

Answer 1

Answer:

B

Explanation:

We know that the AmpR gene region has been interrupted. So this means the AmpR gene will not function in the recombinant DNA.

But the question tells us that the TetR gene is not interrupted, so the TetR gene will still function.

AmpR represses the protein that confers resistance to ampicillin, and AmpR is no longer functional, so the new bacterial cells will be resistant to ampicillin.

TetR represses the protein that causes resistance to tetracyline, and TetR is still functional, so the new bacterial cells will not be resistant to tetracycline.

This means B, there will be growth on ampicillin but not tetracycline containing media.