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Question
Why is the coding sequence of an enzyme β - galactosidase a preferred selectable marker in comparison to the ones named above?
Solution
The gene for the enzyme β-galactosidase is an alternative selectable marker. When the foreign gene is inserted within the β-galactosidase gene, the enzyme β- galactosidase gets inactivated. Then the bacteria are grown on a chromogenic substrate. Non-recombinants will produce blue-coloured colonies, while recombinants will produce colourless colonies.
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