Biotechnology- Principles and Processes Question 26
26. The colonies of recombinant bacteria appear white in contrast to blue colonies of nonrecombinant bateria because of: [NEET 2013]
(a) Insertional inactivate of alphagalactosidase in non-recombinant bacteria
(b) Insertional inactivation of alphagalactosidase in recombinant bacteria
(c) Inactivation of glycosidase enzyme in recombinant bacteria
(d) Non-recombinant bacteria containing beta-galactosidase
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Answer : d
Hints & Solutions
(d) Alternative selectable markers have been developed which differentiate recombinant from non-recombinants on the basis of their ability to produce colour in the presence of chromogenic substrate. In this, a recombinant DNA is inserted within the coding sequence of an enzyme $\beta$-galactosidase. This results into inactivation of the enzyme, which is referred to as insertional inactivation. The presence of chromogenic substrate give blue coloured colonies of the plasmid in the bacteria does not have an insert. Presence of insert results into insertional inactivation of the galactosidase and the colonies do not produce any colour, these are identified as recombinant colonies. Insertional inactivation is a technique used in recombinant DNA technology and involves inactivation of a gene by inserting a fragment of DNA into the middle of its coding sequence.
