Question

In a Drosophila polytene chromosome just before molting you add green labelled antibody against unphosphhorylated RNA pol II CTD and red labelled antibody against phosphorylated RNA pol II CTD. These give fluorescence on adding the respective substrates. What will be the colour in gene 74 EF and 75 B?

(a) Red

(b) Green

(c) Yellow

(d) Magenta

This question was addressed to me by my college director while I was bunking the class.

Query is from Transcription in Eukaryotes : RNA Polymerases in division Gene Expression : Transcription Prokaryotes of Cytogenetics

Answer 1

Correct answer is (a) Red

To elaborate: The 74EF and 75B genes are highly transcribed during and before molting. Thus, there would be many RNA pol II with phosphorylated CTD there which will bind the red labelled antibody. Yellow colour is seen when red and green fluorescence mix.