Question

Please explain which one I missed, I got a 8/10. Might be the last question that I missed!

ament Quiz -U01-202020 Fund of Biology | The Meselson-Stahl experiment demonstrated that DNA replication produces two DNA molecules each composed of _? Select one a One Old stand of nucleotides and One new strand of nucleotides b. A varying number of strands of old and new nucleotides Two strands of old and new nucleotides mixed d. Two new strands of nucleotides e. Two old stands of nucleotides What will E. coli cells produce in an experiment testing bands produced in density gradient centrifugation and starting with 'N DNA, after THREE generations in the medium? Select one a one band of light DNA and one band of DNA with medium density b three bands corresponding to DNA of light, medium and heavy density c. a single band of DNA with medium density d. one band of heavy DNA and one band of light DNA e one band of heavy DNA and one band of DNA with medium density Starting with 'N DNA, and after ONE generation in the "'N medium, E.col cells subjected to density gradient centrifugation will produce a single band of DNA with medium density Select one True d) 521 PM

Answer 1

Answer :

All your responses are correct, except the last one.

It is given that what would the result be if replication were conservative. In conservative replication, when a parent cell divides into two daughter cells, then one of the daughter cell contains both parental DNA strands, whereas the other daughter cell contains a completely newly synthesized DNA duplex.

Hence, when a bacteria with 15N15N is grown for one generation in 14N medium, then after one round of (conservative) replication daughter cells will be of the following two types :

One daughter cell with 15N15N (completely parental) and other daughter cell will be 14N14N (completely new).

Hence, we will observe one heavy band (15N15N) and one light band (14N14N).

Correct choice:

d. two bands, one heavy and one light.

All the best!!