Before You Begin
Question #47712
The Question
A researcher uses the pBR322 plasmid vector to clone a foreign gene, ligating the insert specifically at the Pst I restriction site. After the transformation of competent E. coli cells, the researcher directly plates the entire mixture onto an agar medium containing only ampicillin to isolate the recombinants. Which of the following will be the exact outcome of this plating strategy?
Options
- A.
Only the recombinant transformants will form colonies, as they possess the foreign DNA.
- B.
Both recombinant and non-recombinant transformants will form colonies due to the presence of the plasmid.
- C.
Only non-recombinant transformants will form colonies, while the desired recombinants will perish.
- D.
Neither recombinants nor non-recombinants will grow, as tetracycline is required for plasmid replication.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Regulatory_Failure
Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.
Concepts Behind This Question
DNA Ligase Polarity|Restriction Enzyme Cleavage Physics|Plasmid vs Chromosomal DNA
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize that 'plasmids confer antibiotic resistance' and mistakenly assume that plating on the corresponding antibiotic selects FOR the recombinant.
They fail to synthesize that insertional inactivation destroys that specific resistance, turning the antibiotic into a lethal trap for the desired recombinants.
To recover recombinants in this scenario, one must first plate on tetracycline (to eliminate non-transformants) and then replica-plate on ampicillin (where recombinants are identified by their inability to grow).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biotechnology : Principles and Processes - Class 12 |
| Concept | DNA Ligase Polarity |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |