MCDB 101A Summer 2023 Exam 1.

In this set of multiple-choice questions, the following answers were selected: The process that requires RecA is the formation of an Hfr strain, a specialized transducing phage, and an F prime strain (e. b, c, and d). The primary factor that determines the possibility of measuring cotransduction frequency between two genetic markers is the number of homologous regions located between the markers (a). The process that plays the most significant role in the formation of multi-drug-resistant plasmids is conjugation (e). The ordered clone method of genomic sequencing involves fragmenting the genome into small pieces, sequencing all cloned fragments, and using restriction enzyme mapping for physical mapping of the entire genome (c). Recombination events during transduction will fail to yield viable cells if there are an odd number of crossover events (b). An Hfr strain is produced by the integration of an F plasmid into the E. coli genome (d). The transfer of gal genes from one genome to another by λdgal occurs through specialized transduction (d). Resolvase is utilized in the transfer of F plasmid DNA during conjugation and integration of Hfr DNA into a new host genome (e). Additionally, the class of mutations resulting from the insertion of a transposon into a gene is frameshift/insertion mutation. The autoradiogram of a DNA sequencing gel suggests an imprecise transposition event as there are no directly repeated sequences or direct repeats at the transposon location. In the given cotransduction problem, the A-C cotransduction frequency (0.678) is higher than the D-C cotransduction frequency (0.600), indicating that the markers A and C are closest to each other. This is because cotransduction frequency is inversely proportional to distance. Lastly, the plasmid map constructed based on the given fragments shows the distances between the restriction sites for enzymes A and C relative to the site for enzyme B. Overall, these questions cover various topics such as genetic processes, sequencing methods, transposons, and mapping techniques.