First Experiment

1		A Harlequin chromosome is
			A)	A pair of homologous chromosomes
			B)	A pair of sister chromatids
			C)	An unreplicated chromosome during interphase
			D)	None of the above.
2		One round of DNA replication in the presence of BrdU produces one sister chromatid in which one DNA strand contains BrdU and the other sister chromatid with
			A)	Both strands containing BrdU
			B)	Neither strand containing BrdU
			C)	Only one strand containing BrdU
			D)	None of the above
3		In the absence of crossing over, two rounds of DNA replication in the presence of BrdU produce one sister chromatid in which one DNA strand contains BrdU and the other sister chromatid with
			A)	Both strands containing BrdU
			B)	Only one strand containing BrdU
			C)	Neither strand containing BrdU
			D)	None of the above
4		Hoechst33258 and Giemsa bind
			A)	Equally to both sister chromatids
			B)	More tightly to the chromatid with one DNA strand containing BrdU
			C)	More tightly to the chromatid with both DNA strands containing BrdU
			D)	None of the above
5		Certain types of mutagens increase the rate of sister chromatid exchange. If we assume that a mutagen only exerts its effects for a brief period, when should the mutagen be added to observe sister chromatid exchange according to the procedure described in this experiment?
			A)	Before the first round of DNA replication
			B)	After the first round but before the second round
			C)	After the second round
			D)	After the addition of Hoeschst 33258 and Giemsa

Second Experiment

6		In McClintock's cross in which Ds was inserted into the C gene, most of the kernels had a white background with red sectoring. The red sectoring was due to
			A)	Chromosome breakage
			B)	Excision of Ds and re-ligation of the two ends of the chromosome
			C)	Extrachromosomal inheritance
			D)	None of the above
7		In McClintock's cross in which Ds was inserted into the C gene, the formation of a completely red kernel was due to
			A)	Chromosome breakage during the growth of the kernel
			B)	Chromosome breakage during pollen formation
			C)	Excision of Ds during the growth of the kernel
			D)	Excision of Ds during pollen formation
8		As described in the introduction to this experiment, McClintock had a strain in which Ds was between CI and the centromere. In that strain, red sectoring was due to chromosome breakage. How would the excision of Ds and the re-ligation of the two ends of the chromosome affect the kernel phenotype?
			A)	It would not cause red sectoring.
			B)	It would cause red sectoring.
			C)	It would change the starchy/waxy phenotype.
			D)	It would change the normal/shrunken endosperm phenotype.
9		If McClintock had carried out the exact same cross in which Ds was inserted into the C gene, but the strain was missing the Ac locus, how would that have affected the results?
			A)	There would be no effect.
			B)	The kernels would be all white.
			C)	The kernels would be all red.
			D)	The kernels would have a red background with white sectoring.
10		Evidence that Ds had moved out of the C gene and into another location was
			A)	The red phenotype was stable and chromosome breakage did not occur at a new location.
			B)	The red phenotype was unstable and chromosome breakage occurred at a new location.
			C)	The red phenotype was stable and chromosome breakage occurred at a new location.
			D)	The red phenotype was unstable and chromosome breakage did not occur at a new location.