Question

Bacteria are grown in 15N (heavy) medium and then transferred to 14N (light) medium and are allowed to replicate for 1 generation. The DNA is subsequently isolated and centrifuged in a CsCl2 gradient to yield what type of gradient band(s)?a. one intermediate bandb. one heavy and one light bandc. one heavy bandd. one light bande. one heavy and one intermediate band

Answer 1

Answer:

A) one intermediate band

Explanation:

Meselson & Stahl experiment on the E.coli bacteria to identify the mechanism of replication in bacteria.

For this, they grew bacteria in a heavy isotope of the nitrogen ¹⁵N which allowed the bacteria to take ¹⁵N in their DNA. They then grew the bacteria into ¹⁴N which allowed the bacteria now to take ¹⁴N in their DNA.

When they allowed the bacterial population to replicate their genome for one generation they found that their genome contained both types of isotopes of nitrogen in their DNA through centrifugation.

Since after the centrifugation only one band was observed which contains both the form of the nitrogen, therefore, the band was called intermediate band with intermediate density.

Thus, Option-A is the correct answer.