Question

Looking at the gel electrophoresis of pcDNA vector digestion with no enzyme, Xbal, or EcoRI below, answer the following question (#76). Remember pcDNA vector has both Xbal and EcoRI restriction enzyme sites within the multiple cloning sequence. GELA no enz Xbal Eceri ladder GEL B no enz_Xbal EceRl ladder 76. Which gel showed successful digestion (cutting) of the vector? A. Gel A B. Gel B C. Both A and B D. Neither Gel A or B E. Gel electrophoresis is not an appropriate method to determine if DNA has been cut (or digested) by restriction enzymes. 77. The Tm is A. the temperature at which 12 of dsDNA molecules become ssDNA B. the time it takes for 12 of dsDNA molecules become ssDNA C. the temperature at which all dsDNA molecules become ssDNA D. the temperature at which all ssDNA molecules become dsDNA E, the time it takes for all ssDNA molecules to become dsDNA

Answer 1

76. Gel A represents successful digestion . pcDNA is a plasmid DNA that is circular DNA that move slowly through the gel and when digested with a restriction enzyme become linear so it will move fast and appear low in gel lane . In Gel A both the DNA treated with restriction enzymes become linear and moved faster therefore present at lower position when compared with bands in no enzyme gel.

Gel B : there is no difference in the no enzyme and enzyme treated DNA . Bands in all three lanes are appearing at same position.

77. Tm is the melting temperature at which half of the dsDNA molecules become ssDNA.