Question

You generate a fluorescent probe against a gene that has been deleted. You expose the DNA to the probe and observe it under fluorescent microscope. What will you see?

(a) Fluorescence will correspond to the gene of interest

(b) There will be a number of regions that emit fluorescence

(c) Most parts of the chromosome emits fluorescence

(d) Nothing is seen under fluorescence microscope

I had been asked this question in semester exam.

This is a very interesting question from Chromosomal Abnormalities : Deletion topic in division Chromosomal Basis of Inheritance of Cytogenetics

Answer 1

Right answer is (d) Nothing is seen under fluorescence microscope

Easiest explanation: The gene corresponding to the probe labeled with fluorescence is deleted. Thus, probe can’t bind the DNA. In this case no fluorescence should be seen on the chromosome.