Question

When biologists conduct transformation experiments, they are concerned that the cells receiving the plasmid could already be resistant to the antibiotic used. For example, in this experiment, it is possible that a small fraction of the E. coli cells were already resistant to ampicillin. If true, the colonies seen on the NA-AMP plates in part A would NOT be actual transformants, but rather – just natural variants of the E. coli cells. Due to this concern, experimental controls are performed: in this case, to check on whether there are any ampicillin–resistant E. coli before adding the pGRN plasmid. As you were performing the above transformation experiments, you have followed the same procedure, except you have replaced the pGRN plasmid with water. Predict what you might expect to see if you plate these reactions on NA and NA- AMP plates.

	Colony count (0, 50, or 10,000)	Colony Color under UV
NA
NA-AMP

Which plate, according to your prediction, will have more colonies, NA or NA-AMP? Why?

Do you expect to see colonies on NA-AMP plates? Why or Why not?

What information can you gather by plating E. coli cells on NA and NA-AMP?

Answer 1

Which plate, according to your prediction, will have more colonies, NA or NA-AMP? Why?

Ans: The NA plate will have more colonies because all E.coli will grow on it. NA-AMP plates will have fewer colonies because only few natural variant E.coli might show AMP resistance among all E.coli plated

Do you expect to see colonies on NA-AMP plates? Why or Why not?

Ans: If any natural variant E.coli already having AMP resistance, I expect to see colonies, if no AMP resistance characteristic no colonies will be seen

What information can you gather by plating E. coli cells on NA and NA-AMP?

Ans: By plating on NA and NA-AMP we can get the information of how many bacteria (colonies) are natural varients for AMP resistance and how many are not. By sustracting NA-NA-AMP will get the natural trvarients for AMP resistance. On NA plate all e.coli will grow, from the table let’s say 10,000 colonies, on NA-AMP let’s say 50 colonies grown, now we can say that 9950 colonies are normal without AMP resistance and among 10000 colonies 50 are naturally AMP resistant.