Question

To do a semi-quantitative PCR analysis, you measured the intensity of bands on your gel (mean pixel intensity – unitless number) and got the following results: NMDA (control) 15, GAPDH (control) 300, NMDA (experimental) 50, GAPDH (experimental) 250. By what factor did the expression of NMDA change from control to experimental?

Answer 1

Ans: Since the numbers we have here are pixel densities of bands on a gel, which are commonly measured by freely available softwares developed by companies who supply densitometers. These numbers are unitless as mentioned and different softwares may generate different numbers but ratios should remain same.

So here the control NMDA is 15 which increases to 50 under experimental conditions-

Therefore 50/15= 3.3333

So an increase of ~3.333 times