The bacteriophage lambda chromosome has several A:T-rich segments that denature when exposed to pH 11.05 for 10 minutes. After such partial denaturation, the linear packaged form of the lambda DNA molecule has the structure shown in Figure 10.9a. Following its injection into an E. coli cell, the lambda DNA molecule is converted into a covalently closed circular molecule by hydrogen bonding between its complementary singlestranded termini and the action of DNA ligase. It then replicates as a q-shaped structure. The entire lambda chromosome is 17.5 mm long. It has a unique origin of replication located 14.3 mm from the left end of the linear form shown in Figure 10.9a. Draw the structure that would be observed by electron microscopy after both (1) replication of an of the lambda chromosomal DNA molecule (in vivo) and (2) exposure of this partially replicated DNA molecule to pH 11.05 for 10 minutes (in vitro), 

(a) If replication had proceeded bidirectionally from the origin, and 

(b) If replication had proceeded unidirectionally from the origin.approximately 6-mm-long segment