Question

A scientist is using an ampicillin-sensitive strain of bacteria that cannot use lactose because it has a nonfunctional gene in the lac operon. She has two plasmids. One contains a functional copy of the affected gene of the lac operon, and the other contains the gene for ampicillin resistance. Using restrictions enzymes and DNA ligase, she forms a recombinant plasmid containing both genes. She then adds a high concentration of the plasmid to a tube of the bacteria in a medium for bacterial growth that contains glucose as the only energy source. This tube ( ) and a control tube (-) with similar bacteria but no plasmid are both incubated under the appropriate conditions for growth and plasmid uptake. The scientist then spreads a sample of each bacterial culture ( and -) on each of the three types of plates indicated below.

1. If no new mutations occur, it would be most reasonableto expect bacterial growth on which of the following plates?
a) 1 and 2only
b) 3 and 4 only
c) 5 and 6 only
d) 4, 5, and 6 only
e) l, 2, 3, and 4only

Answer 1

E: 1, 2 3, and 4 will all grow.

Step-by-step explanation:

E: 1, 2 3, and 4 will all grow.

This is because the plasmid gave the bacteria resistance to ampicillin and allowed it use lactose.

The fact that the plasmid had a functional +lac gene was not relevant because glucose was present in all cases, so that lactose was not used as a means of selection. Only ampicillin resistance was a means of selection in this experiment, which is why #5 and #6 were susceptible.