To prove that DNA carries genetic information, a transformation experiment on E

Question

To prove that DNA carries genetic information, a transformation experiment on E coil was performed using a plasmid, pGLO which has an ampicillin resistant gene and a green fluorescent (GFP) gene. Transformed cells (indicated by pGLO +) were plated on LB containing ampicillin (LB amp) and on LB containing ampicillin and arabinose (LB amp ara). A control experiment was performed without plasmid. pGLO. After overnight incubation of E coil cells, growth of experiments and phenotypic change of transformed cells were recorded in the Table below. Provide an explanation for the results on each plate in the space provided in right side column.

Explanation / Answer

Answer:

Based on given information:

Explanation for results:

1) pGLO- , LB, Heavy growth: In this case, there is no ampicillin added to LB media. Even though transformation has not taken place, still E.coli can grow easily in LB. Since doubling time of E.coli is short (~20min in optimal condition s) therefore after overnight incubation lot of colonies will be observed.

2) pGLO-, LB-Ampicllin, No bacterial growth: In this case, since the media LB contains ampicillin and the transformation didnot occur, therefore the E.coli cells do not have ampicillin resistant gene. In the presence of antibiotic ampicillin there will be no growth.

3) pGLO+, LB-Ampicillin, A few colonies: In this case, cells have acquired ampicillin resistant genes from the plasmid pGLO after successful transformation. Since e.coli cells are now resistant to ampicillin therefore few colonies have grown.

4) pGLO+, LB-Ampicllin-Arabinose, A few colonies producing green bright light on UV exposure: In this case, the transformed cells contains genes for both GFP and Ampicillin. In the presence of Arabinose the transcription of GFP occurs as a result of binding of RNA polymerase to Promoter (induced by change in shape of AraC protein). Due to GFP production, the colonies appear bright green upon exposure to UV light.

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