Gurugrah Questions: Your Source for Thoughtful Queries, Your Gateway to Enlightening Answers.
Sequence No.
BIO-470
Answer the following questions based on Meselson and Stahl’s experiment on E.coli.
(i) Write the name of the chemical substance used as the only source of nitrogen in the experiment.
(ii) Why did they allow the synthesis of the light and the heavy DNA molecules in the organism?
(iii) How did they distinguish the heavy DNA molecules from the light DNA molecules?
(iv) Write the conclusion the scientists arrived at the end of the experiment.
Answer:
(i) Ammonium chloride (NH4Cl) with N14 atom.
(ii) It is show that after one generation E. coli with 15N - DNA in a medium of 18 N, has DNA of intermediate density between the light and heavy DNAs. It shows that of the two strands, only one strand is synthesised newly, using the 14 N - nitrogen source in the medium.
(iii) The heavy and light DNA molecule can be differentiated by centrifugation in a cesium chloride (CsCl) density gradient. The 15N - DNA was heavier then 14N - DNA and the hybrid 15N - 14N - DNA was intermediate between the two newly formed DNA strands.
(iv) Scientists concluded that the DNA replication is semiconservative i. e., at the two strands of DNA, one is the parental strand, while the other is newly synthesised.
Reporting Question Sequence No.
BIO-470
Your Report Has Been Successfully Submitted.
Our Team Will Review It Shortly. Thank You for Your Contribution to our Knowledge Hub!
An error occurred. Try again later