A scientist used a radioactive isotope of nitrogen to label the nitrogenous bases of the DNA in bacterial cells. The labeled cells were then allowed to grow and divide for one generation in a medium of non-radioactive nitrogen. Where is the radioactive nitrogen in the DNA of the bacterial cells? A. distributed evenly among all of the DNA B. in both strands of the DNA of half of the cells C. in one strand of the DNA of half of the cells D. in one strand of the DNA of all of the cells

Explanation:

As given here,

The nitrogenous base of DNA is radio active labeled, and is grown in normal unlabeled medium.

As we know that DNA replication occurs in semi-conservative way, so after one round of replication, one parental strand would be radio active and other newly synthesized strand would be unlabeled.

So here, after one round of replication, one strand of all the newly synthesized DNA would be radio active and other strand would be normal.

b) chemical ( the chemical breakdown of food is accomplished by enzymes. )

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