Draw the colonies AND answer the mutiple choice question bel

Draw the colonies AND answer the mutiple choice question below:

The experiment demonstrates that:

a. A new environment (antibiotic) creates beneficial mutation in all individuals.

b. A new environment creates beneficial mutation in some indivuduals

c. The beneficial mutation must have existed prior to enviorment change.

5. (3 pts) In the experiment shown below, several replica plates containing the antibiotic were made from the \"No anti biotic\" plate. Replica Plate A shows the colonies that grew. Carefully draw the colonies that will grow on Replica Plates B, C and D. (All of the replica plates have antibiotic) Replica Plate B No antibiotic Replica Plate A Replica Plate D Replica Plate C

Solution

Choice b is correct.

Reason: In a microbiological assay, antibiotic treatment is applied to ascertain the antibiotic resistance of a microbe. In such experiments, initially no antibiotic is applied in the master culture and it is subcultured into three or four plates. The sub-culture plates are then incubated with various dilutions of an antibiotic and allowed to grow. These plates are then observed for changes in pattern of growth. Using different dilutions of the antibiotic, one can investigate whether the antibiotic is able to kill the microbes or not. If the antibiotic is capable of killing the microbes, the exact dilution of this antibiotic can also be determined since different dilutions of antibiotics have been applied in different sub-culture plates.

Now according to the question, a master plate without antiobiotic treatment is replicated and plate A contains antiobiotic where some colonies appeared. Importantly, antibiotic treatment was also applied in rest of the plates and no colonies appeared in them. This observation clearly states that colonies appearing on plate A were resistant to this antibiotic whereas absence of colonies in rest of the plates clearly shows that remaining colonies were susceptible to this antibiotic. Thus, no colony will appear in any of the plates B,C or D. This also depicts that the antibiotic treatment created a beneficial mutation for some of the colonies just after application of antibiotic. This is why some colonies could grow in antibiotic treatment whereas some could not.