NEET2026BiologyChapterActual
A foreign DNA fragment was ligated at the BamH I restriction site of the pBR322 cloning vector. The resulting recombinant plasmids were introduced into host E. coli cells. The selection of recombinants was carried out as per the given flowchart. Which of the following correctly represents the growth behavior of the recombinant transformants during this selection process?
Options
- AThey will form colonies on Plate 1 but will not survive on Plate 2.
- BThey will form colonies on both Plate 1 and Plate 2.
- CThey will not survive on either Plate 1 or Plate 2.
- DThey will not survive on Plate 1 but will form colonies on Plate 2.
Correct answer
A. They will form colonies on Plate 1 but will not survive on Plate 2.
Step-by-step solution
The pBR322 cloning vector contains two antibiotic resistance genes: ampicillin resistance ( amp^R ) and tetracycline resistance ( tet^R ). The BamH I restriction site is located within the tetracycline resistance gene ( tet^R ). When a foreign DNA fragment is ligated at the BamH I site, it disrupts the tet^R gene, leading to its insertional inactivation. As a result, the recombinant plasmids lose their resistance to tetracycline but retain their resistance to ampicillin. When these recombinant plasmids are introduc