Protein synthesis in an animal cell occurs -

Which one of the following makes use of RNA as a template to synthesize DNA -

E. coli cells with a mustard z gene of the lac operon cannot grow in medium containing only lactose as the source of energy because -

Using imprints from a plate with complete medium and carrying bacterial colonies, you can select streptomycin resistant mutants and prove that such mutations do not originates as adaptation. These imprints need to be used -