Question
How does $\beta$-galactosidase coding sequence act as a selectable marker? Explain. Why is it a preferred selectable marker to antibiotic resistance genes?
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Answer
- Presence of a chromogenic substrate gives blue colour, if the plasmid in the bacteria does not have an insert. (non-recombinants)
- With the insert do not produce any colour, recombinant colonies.
- Selection of recombinants due to inactivation of antibiotics, requires simultaneous plating on two plates having different antibiotics/process is more cumbersome.
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