An EColi Cell Whose DNA Contains N¹⁴ Is Placed in Media

question 39

Multiple Choice

An E.coli cell whose DNA contains N¹⁴ is placed in media with dNTPs containing a heavy isotope of nitrogen,N¹⁵,which incorporates into newly synthesized DNA.After one cell division,what will the DNA in the daughter cells look like?

• A) One cell will have both strands of the helix N14; the other cell will have both strands of the helix N15.
• B) One cell will have mostly N14 with a little bit of N15; the other cell will have mostly N15 with a little N14.
• C) Each cell will have one strand of N14 and one strand of N15.
• D) It is impossible to predict what the DNA in the daughter cells will look like.

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