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Cell Biology: DNA and Viruses

1. Bacteriophage M13 infects E. coli differently from the way bacteriophage T2 does. The M13 coat is removed in the inner membrane of the bacterial cell, where it is sequestered during phage replication. It is subsequently used to package the newly replicated phage DNA to create progeny phage. Why would this make M13 less suitable than T2 for the Hershey and Chase experiment?

2. Adenovirus has a double-stranded linear DNA genome that measures 12.2 m in length. How many base pairs make up the adenovirus genome?

3. A DNA is found to exhibit a melting point of 75C in 0.1 M NaCl. What effect would each of the following have on the malting point of the DNA?

a. Increased NaCl
b. Decreased DNA concentration
c. Adding 1% formamide

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Solution Preview

I will answer your molecular biology questions with a little bit of background so that you can understand the important concepts.

#1. To understand this question it is important to understand the "Hershey Chase" experiment. This experiment set out to determine what was the unit of heredity in a cell: nucleic acid or protein? Now of course we know that the answer is nucleic acid (specifically DNA), but this experiment came at a time when this was still being determine.
In 1952, A.D Hershey and Martha Chase performed this following historic experiment:
Using bacteriophage (virus that infects bacteria) T2 (which ONLY contains DNA and protein), they set out to determine whether the genes reside in the DNA of the protein. They ...