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.

What would the expected effect be on a PCR reaction if the primers used were slightly shorter and more variable than the intended oligonucleotide sequences?

#Question id: 4507

#Unit 3. Fundamental Processes

A group of introns that-unlike those we have considered thus far-can splice themselves out of pre-mRNA without the need for the spliceosome, they are called

#Question id: 4508

#Unit 3. Fundamental Processes

Statement: In the case of group II introns, the chemistry of splicing and the RNA intermediates produced are the same as those for nuclear pre-mRNA.

 Explanations: I. The intron uses an A residue within the branch site to attack the phosphodiester bond at the boundary between its 5’ end and the end of the 5’ exon-that is, at the 5’ splice site. This reaction produces the branched lariat.

II. A second reaction in which the newly freed 3’ -OH of the exon attacks the 3’splice site, releasing the intron as a lariat and fusing the 3’ and 5’ exons.

#Question id: 4509

#Unit 3. Fundamental Processes

Which group of introns contain an “internal guide sequence”

#Question id: 4510

#Unit 3. Fundamental Processes

Which statements are true about group I and group II introns,

A. Group I (and II) introns are not enzymes because they have a turnover number of only 1.

B. A third transesterification reaction can occur to cyclize the intron.

C. They cannot be readily converted into ribozymes.

D. It is similar to the way that the self-cleaving Hammerhead could be converted to a ribozyme by separating the active site from the substrate

#Question id: 4511

#Unit 3. Fundamental Processes

The proteins are not needed for the splicing reaction itself, because

#Question id: 4512

#Unit 3. Fundamental Processes

Some pre-mRNAs can be spliced in more than one way. Thus, mRNAs containing different selections of exons can be generated from a given pre-mRNA, called