Selection of recombinants due to inactivation of antibiotics is a cumbersome procedure because it requires simultaneous plating on two plates having different antibiotics. Therefore, alternative selectable markers have been developed which differentiate recombinants from non-recombinants on the basis of their ability to produce colour in the presence of a chromogenic substrate.WHAT DOES IT MEAN ?
- After the insertion of alien DNA, the recombinant plasmids lose the antibiotic resistance, that is they get inactivated. Whereas the non recombinants still have both the antibiotic resistance genes.
- So now we know the difference between the recombinants and the non-recombinants, but to check this we need to plate these at the same time in different plates with the different antibiotic resistance genes.
- We need to observe what is growing where and what is not growing so this is quite a tiring or time-consuming procedure.
- Hence, other selectable markers have been developed which are much easier to use.
- Since, they easily differentiate recombinants from the non-recombinants as the recombinants do not have the ability to produce colour in presence of a chromogenic substrate. Non-recombinants can produce colour.