First Experiment

1		In this experiment, the purpose of CsCl gradient centrifugation is to
			A)	Denature the DNA
			B)	Separate DNA containing 14N from DNA containing 15N
			C)	Separate replicated DNA from nonreplicated DNA
			D)	Determine the length of DNA fragments
2		What is the purpose of adding EtBr and exposing the gradients to UV light?
			A)	To denature the DNA
			B)	To visualize the DNA
			C)	To convert 14N to 15N
			D)	To lyse the cells
3		What are the expected proportions of light versus half-heavy DNA after four generations according to the semiconservative model?
			A)	1 light : 1 half-heavy
			B)	3 light : 1 half-heavy
			C)	7 light : 1 half-heavy
			D)	15 light : 1 half-heavy
4		If the conservative model had been correct, what would have been the expected results after three generations?
			A)	All light
			B)	3 light : 1 heavy
			C)	7 light : 1 heavy
			D)	7 light : 1 half-heavy
5		If the dispersive model had been correct, what would have been the expected results after three generations?
			A)	All light
			B)	All ¼ heavy
			C)	7 light : 1 half-heavy
			D)	All 1/8 heavy

Second Experiment

6		If the perchloric acid step had been omitted from this experiment, how would that have affected the results?
			A)	More radioactivity in the supernatant
			B)	More radioactivity in the pellet
			C)	Less radioactivity in the supernatant
			D)	No effect on the results
7		If helicase had been omitted from this experiment, new DNA strands could still be made if
			A)	RNase was also added.
			B)	Single-stranded DNA was added.
			C)	More primase was added.
			D)	More DNA polymerase was added.
8		If DNA primase had been omitted from this experiment, new DNA strands could still be made if
			A)	RNase was also added.
			B)	Single-stranded DNA was added.
			C)	Primers were added.
			D)	More helicase was added.
9		The purpose of the centrifugation step is to
			A)	Denature the DNA
			B)	Promote the synthesis of new DNA strands
			C)	Separate the DNA from free nucleotides
			D)	Remove the DNA polymerase
10		Consider the strategy of isolating temperature-sensitive mutants that have defects in particular proteins involved in DNA replication. Let's suppose a ts-mutation affected the functioning of DNA polymerase III and this strain was used to make a cell extract for an in vitro replication system. DNA replication would occur at the higher (nonpermissive) temperature in the in vitro system if
			A)	Purified DNA polymerase was added from a nonmutant strain
			B)	Purified DNA primase was added from a nonmutant strain
			C)	Purified DNA helicase was added from a nonmutant strain
			D)	None of the above