The E. coli chromosome contains approximately 4 × 10⁶ nucleotide pairs and replicates as a single bidirectional replicon in approximately 40 minutes under a wide variety of growth conditions. The largest chromosome of D. melanogaster contains about 6 × 10⁷ nucleotide pairs.

(a) If this chromosome contains one giant molecule of ONLINE_DNA that replicates bidirectionally from a single origin located precisely in the middle of the DNA molecule, how long would it take to replicate the entire chromosome if replication in Drosophila occurred at the same rate as replication in E. coli? 

(b) Actually, replication rates are slower in eukaryotes than in prokaryotes. If each replication bubble grows at a rate of 5000 nucleotide pairs per minute in Drosophila and 100,000 nucleotide pairs per minute in E. coli, how long will it take to replicate the largest Drosophila chromosome if it contains
a single bidirectional replicon as described in (a) above?
(c) In Drosophila embryos, the nuclei divide every 9 to 10 minutes. Based on your calculations in (a) and (b) earlier, what do these rapid nuclear divisions indicate about the number of replicons per chromosome in Drosophila?