Question

7. You have performed a cloning experiment in which you digested genomic DNA from starfish cells with an enzyme and ligated the fragments into plasmid vectors digested with the same enzyme. The plasmid you are using contains a gene for ampicillin resistance and an MCS located within the Lacz gene. For the ligation, you added three times as much of the digested plasmid as the insert. After introducing the ligated DNA into cells, you observe 200 blue colonies and 33 white colonies. Describe what these results mean? Would you be satisfied with these results? Explain why or why not. Write your answer in complete sentences. I

Answer 1

Ans- LacZ gene codes for an enzyme $\beta$ -galactosidase which is responsible of breaking substrate X-gal(added to media) and producing colored product i.e blue. If lacZ gene is inactivated, no enzyme will be formed so, there will be no blue color.

Since, the MCS is located in LacZ gene, if our gene of interest is introduced in MCS, lacZ is inactivated leading to white colonies.

Therefore, white colonies indicate recombinant bacteria while blue colonies indicate non-recombinant bacteria. Getting 33 recombinant colonies is good number.

I will be satisfied with results because we have enough recombinant colonies to screen and find the one with our gene of interest.