Part 1. Bob plans to prepare the TWO kinds of competent cells. DH5a and DH10B. for plasmid transformation. Here is theprotocol he found from cDNA Libeary Protocols. 69.129-137 (1997). He will follow the protocol exactly. Based on the protocol.please answer the following questions. Step 1. Pick a single colony from a plate of cells that have been treshly grown for 16-20 h at 37℃. and transfer it to 50 mL ofLB medium in a sterile 300-mL. flask. Incubate the culture for 16-20 h at 37℃ with moderate shaking. Step 2. Inoculate I mL of the culture into 100 mL. of LB medium in a sterile 500-mL flask. Grow cells at 37℃ for about 3 h withvigorous shaking (300 cycles/min on a rotary shaker).Step 3. Transfer the cells aseptically to two 50-mL prechilled, sterile polypropylene tubes. Leave the tubes on ice (0℃) for 10  min.Step 4. Centrifugc cells at 2400g for 10 min at 4℃. Stcp 5. Pour off the supernatant, resuspend each pellet of cells in 10 mL of ice-cold 0.1M CaCl2, and store on ice. Step 6. Recover the cells by centrifugation at 2400g for 10 min at 4℃. Discard the supernatant. and resuspend each pellet in 10mL of an ice-cold solution of 0.1 M CaCl2. Keep the resuspended cells on ice for 30 min. Step 7. Centrifuge cells at 2400g for 10 min at 4℃. Discard the supernalant. and resuspend cach pellet in 2 mL of the ice-coldsolution of 0. 1M CaCl2 Step &. Dispense cells and aliquot them (250 μL/tube) into prechilled. sterile polypropylene tubes. Frecze immediately at -70℃.
【題組】1. How many flasks will Bob use while preparing TWO competent cells? (3%)
(A) 2
(B) 4
(C) 6
(D) 8