Question

You want to find out which of the consequent gene X or Y is being transcribed. For this you do a hybridization competition analysis and plot the radioactivity curve with increasing concentration of the competitor unlabelled mRNA. If the transcribed gene was X, which observation fits your result?

(a) The radioactivity of y decreases while that of x remains the same

(b) The radioactivity of x decreases while that of y remains the same

(c) The radioactivity of x and y decreases

(d) The radioactivity of y decreases while x increases

This question was addressed to me in an online interview.

My enquiry is from Transcription in Prokaryotes : Initiation topic in portion Gene Expression : Transcription Prokaryotes of Cytogenetics

Answer 1

The correct answer is (b) The radioactivity of x decreases while that of y remains the same

Best explanation: As the unlabelled mRNA against X will compete with the labeled one for hybridization the intensity of radioactivity will gradually decrease with increased concentration. But as it will not bind to Y gene the Y labeled mRNA faces no competition and its intensity remains same.