Answer: Option D
:
D
1) The polymerase chain reaction (PCR) is a technique used to amplify a single copy or a few copies of a piece of DNA to millions of copies of that particular DNA sequence.
2) RT-PCR is a technique where a mRNA is taken and then reverse transcriptase acts on it and a cDNA is created which then further acts as a template to PCR
3) Gel electrophoresis is a method for separation and analysis of macromolecules (DNA, RNA and proteins) and their fragments, based on their size and charge.
4) The mRNA from a person is isolated and then a single stranded radiolabelled cDNA is synthesized.This radiolabelled cDNA is then allowed to hybridize with single stranded DNA attached to a solid surface.This DNA on the solid surface of the chip is specific(specified by researcher) .This whole process is called DNA microarray. Therefore the image in question that discribes the statement above is the 4th one that belongs to a DNA microarray. The colors represent relative gene expression.