Q40 / 240 · KCET 2026 · Biology
Given below are two statements.
Statement-I: Restriction enzyme BamHI has its recognition site in $R^{tet}$ region of pBR322.
Statement-II: E.coli having pBR322 with a desired DNA if inserted at BamHI site can grow in medium containing tetracycline.
In the light of the above statements, choose the correct answer from the options given below.
Statement-I: Restriction enzyme BamHI has its recognition site in $R^{tet}$ region of pBR322.
Statement-II: E.coli having pBR322 with a desired DNA if inserted at BamHI site can grow in medium containing tetracycline.
In the light of the above statements, choose the correct answer from the options given below.
- ABoth Statement I and Statement II are true
- BBoth Statement I and Statement II are false
- Correct answerCStatement I is true, but Statement II is false
- DStatement I is false, but Statement II is true
Solution
In the plasmid pBR322, the tetracycline resistance gene ($tet^{R}$) contains recognition sites for the restriction enzymes BamHI and SalI. Therefore, Statement-I is true.
When a desired DNA fragment is inserted at the BamHI site, the tetracycline resistance gene gets disrupted due to insertional inactivation. As a result, the recombinant plasmid loses its resistance to tetracycline. Thus, E. coli host cells containing this recombinant pBR322 will not be able to grow in a medium containing tetracycline. Therefore, Statement-II is false.
Answer: Statement I is true, but Statement II is false
When a desired DNA fragment is inserted at the BamHI site, the tetracycline resistance gene gets disrupted due to insertional inactivation. As a result, the recombinant plasmid loses its resistance to tetracycline. Thus, E. coli host cells containing this recombinant pBR322 will not be able to grow in a medium containing tetracycline. Therefore, Statement-II is false.
Answer: Statement I is true, but Statement II is false
Hence, the correct answer is option: 'C'.