Q. Why Meselson and Stahl took ¹⁵N instead of ¹⁴N for their experiment to prove semiconservative replication in E. coli?
A) ¹⁵N is a radioactive isotope and can be easily detected in newly synthesized DNA.
B) ¹⁵N is a heavy isotope of ¹⁴N and it can be separated from ¹⁴N based on density during centrifugation.
C) Only ¹⁵N has the ability to form complementary strands with E. coli template strands.
D) ¹⁴N do not exist in nature while ¹⁵N is found in abundance.
Explanation
¹⁵N is a heavy isotope of ¹⁴N and they both can be separated based on their densities by density gradient centrifugation. In such way, heavy DNA containing ¹⁵N could be distinguished from normal DNA.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.