Question

In an experiment, you are trying to pull down the site where guanyl transferase binds by co-immunoprecipitation. You run a gel and autoradiograph to see a band denoting GSK-RNA pol II (phosphorylated). What will you see when you perform the same experiment with overexpression of GSK in one setup and overexpression of unlabelled GSK-RNA pol II in the other setup?

(a) Band is observed in both cases

(b) Band in 1^st case no band in 2^nd

(c) No band in 1^st case and band in 2^nd

(d) No band in both cases

I got this question by my school principal while I was bunking the class.

The origin of the question is Post-Transcriptional Modification in chapter Gene Expression : Transcription Prokaryotes of Cytogenetics

Answer 1

Correct option is (a) Band is observed in both cases

The explanation is: There will not be any change in the intensity of the 1^st band as GT is not binding to GSK tag. The 2^nd case also doesn’t change the intensity of the band as GT binds to phosphorylated –GSK-RNA pol II, so no GT bound unlabelled RNA exists to compete with the labeled band and decrease its intensity.