Biology Life on Earth Study Set 1
Quiz 12 :
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Q96 Q96 Q96
Suppose a scientist working on a new drug for cancer developed a chemical that irreversibly breaks the hydrogen bonds in the DNA molecules within cancerous cells but leaves all of the covalent bonds intact. Hydrogen bonds are relatively weak compared to covalent bonds, and they are routinely broken and reformed as the DNA molecule is replicated in a normal cell. Their stability is nonetheless critical for maintaining certain aspects of the structure and function of the DNA molecule. Based on this scenario and your knowledge of DNA, how would this newly discovered chemical affect the ʺmolecule of heredityʺ in a human cancer cell?
Q97 Q97 Q97
Bacterial cells have only one DNA molecule, which is double stranded and is replicated in essentially the same fashion as in eukaryotes. Imagine that, following the techniques of other scientists studying DNA, you created a bacterial cell that contains only radioactive nitrogen in its DNA. You then place the cell in a culture medium containing only ʺregularʺ (nonradioactive) nitrogen. Based on this scenario and your knowledge of DNA structure and replication, how many cells will contain some DNA with radioactive nitrogen after four rounds of cell replication?