Question

A eukaryotic gene has "sticky ends" produced by the restriction endonuclease EcoRI. The gene is added to a mixture containing EcoRI and a bacterial plasmid that carries two genes conferring resistance to the antibiotics ampicillin and tetracycline. The plasmid has one recognition site for EcoRI located in the tetracycline resistance gene. This mixture is incubated for several hours, exposed to DNA ligase, and then added to bacteria growing in nutrient broth. The bacteria are allowed to grow overnight and are streaked on a plate using a technique that produces isolated colonies that are clones of the original. Samples of these colonies are then grown in four different media: nutrient broth plus ampicillin, nutrient broth plus tetracycline, nutrient broth plus ampicillin and tetracycline, and nutrient broth without antibiotics. Bacteria containing a plasmid into which the eukaryotic gene has been inserted would grow in which of the following conditions?A) in the nutrient broth plus ampicillin, but not in the broth containing tetracycline. B) only in the broth containing both antibiotics. C) in the broth containing tetracycline, but not in the broth containing ampicillin. D) in all four types of broth. E) in the nutrient broth without antibiotics only.

Answer 1

D) in all four types of broth

Step-by-step explanation:

as the plasmid have antibiotic resistance gene for both the antibiotics, so the bacteria transformed with the plasmid gene will show resistance against ampicillin and not tetracycline because there is restriction site for EcoR1 inside the tetracycline resistance gene and after ligation inside this region will inhibit the resistance to tetracycline. but the plasmid without gene of interest will grow in media containing tetracycline and ampicillin resistance.

1. Nutrient broth plus ampicillin ( as plasmid have an ampicillin resistance gene)

2. nutrient broth plus tetracycline ( as plasmid without insert have an tetracycline resistance gene)

3. nutrient broth plus ampicillin and tetracycline ( as plasmid have resistance gene for both)

4. nutrient broth without antibiotics ( if there is no antibiotic, the bacteria with plasmid transformed and without transformed will both grow)