Practice Questions

B. The enzyme has to make specific interactions with one or all of the DNA template strand, the initiating ribonucleotide, and the second ribonucleotide—holding one (or all) rigidly in the correct orientation to allow chemical attack on the incoming NTP.

C. The structure of the open complex shows that the s region 3/4 linker interacts with the template strand, organizing it in the correct conformation and location to allow initiation.

D. Consistent with this, in experiments using an RNA polymerase containing a s70 derivative lacking this part of s, initiation requires much lower than normal concentrations of one or both of the first two ribonucleotides.

TLS Online TPP Program

#Question id: 13059

#Unit 13. Methods in Biology

Precision will be reduced, but yield will be increased

Optimisation of a PCR reaction is often a compromise between the competing demands for precision, efficiency and yield. Although the specific effects may vary, generally, increasing the annealing temperature will increase non-specific primer binding and reduce precision. Increasing the length of the elongation phase will reduce the proportion of incomplete newly-synthesised strands and therefore increase yield. In this case, the potential effect on efficiency is unclear. Increasing the elongation phase would increase the reaction time, but the time taken to ramp down to a lower annealing temperature would be reduced.

Efficiency during ligation of blunt ended insert and vector cannot be cannot be enhanced by means of…..

TLS Online TPP Program

#Question id: 13083

#Unit 13. Methods in Biology

The genomic DNA of an organism is digested with two restriction enzymes; one of the, PstI (CTGCA/G), while the other., MseI (T/TAA). This would generate the following 3 types of DNA fragments:

(1) both ends cleaved by PstI (Pst-Pst),

(2) both ends cleaved by MseI (Mse-Mse), and