Question

a.) Explain the role of positively charge ions (e.g. Ca²⁺, Li⁺) used during chemical transformation of E. coli and yeast.

b.) What is the role of i) PEG (Polyethylene glycol) and ii) carrier DNA in yeast transformation?

c.) What is phenotypic expression time in transformation procedure? Explain biological background of it.

d.) Briefly describe two groups of selection markers used for microbial transformation: chemical (antibiotic) resistance and auxotrophic. Explain main principles and selection requirements for each group.

e.) Is phenotypic expression time essential in all transformations? Explain using examples for E. coli ampicillin vs kanamycin, for yeast auxotrophic vs antibiotic resistance markers.

f.) While selecting transgenic plants (Arabidopsis) from transformed seeds, we plated/seeded them directly on selective media plates without phenotypic expression time. However we are looking for antibiotic (hygromycin) resistance. Explain why selection from plant seeds does not require phenotypic expression time.