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

1) NA will have more colonies because it supports the growth of both transformants as well as non-transformants.

2) NA-AMP will have fewer colonies because only transformants will grow.

3) by plating E. coli cells on both plates we may able to check the transformant and already resistant E. coli cells.

and with the help of colony counter under UV light we can differentiate between natural AMp resistant cells v/s pGRN transformed E.coli cells on NA-AMP plate.