Biology Practice Problems History of Genetic Research Practice Problems Solution: Which of the following would correctly describe th...

Solution: Which of the following would correctly describe the results of Meselson and Stahl's famous experiment after one cycle of replication in 14N medium, if DNA was conservative?A. DNA molecules containing two 14N-DNA strands only.B. DNA molecules containing one strand of 15N-DNA and one strand of 14N-DNA.C. DNA molecules containing two 15N-DNA strands only.D. DNA molecules containing individual strands composed of a mixture of both 14N-DNA and 15N-DNA.E. An equal number of DNA molecules containing two 15N-DNA and DNA molecules containing 14N-DNA strands.

Problem

Which of the following would correctly describe the results of Meselson and Stahl's famous experiment after one cycle of replication in 14N medium, if DNA was conservative?

A. DNA molecules containing two 14N-DNA strands only.

B. DNA molecules containing one strand of 15N-DNA and one strand of 14N-DNA.

C. DNA molecules containing two 15N-DNA strands only.

D. DNA molecules containing individual strands composed of a mixture of both 14N-DNA and 15N-DNA.

E. An equal number of DNA molecules containing two 15N-DNA and DNA molecules containing 14N-DNA strands.

Solution

The experiment of Matthew Meselson and Franklin Stahl showed the mechanism of DNA replication by growing a culture of E. coli for several generations. They first grew the microorganisms in a medium with 15N-labeled nucleotide precursors. They then transferred it to a medium with 14N precursors. 

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