Question

Describe Meselson and Stahl’s experiment that was carried in 1958 on E.Coli. Write the conclusion they arrived at after the experiment.

Answer 1

semiconservative mechanism of E. Coli.

meson and stahl experiment that was carried out in 1958 :

• they grew e-coli in a medium containing isotopic nitrogen and as the only source of nitrogen for many genrations of E- coli.

• as, a result isotopic nitrogen was incorporated into newly synthesied DNA and the newly formed DNA could be seprated from the original one due to pressence of isotopic nitrogen.

• then they transfered the cells in a medium containing normal nitrogen and took samples at regular intervals , seprated various samples on caseium chloride density gradient to measure densities of DNA.

• the DNA extracted from culture one generation after the transfer of isotopic nitrogen to normal nitrogen medium found to have a hybrid or intermediate densities.

• DNA extracted from culture after another generation was composed of equal amounts of hybrid DNA and light DNA.