Question

A comparative microarray hybridization experiment was performed between normal and cancerous cells. How will you interpret the result obtained on a microarray, if red and green coloured fluors were used for labelling the cDNA probes of normal and cancerous cells respectively?

Hint:

In microarray analysis, red indicates gene expression higher in normal cells, green indicates higher expression in cancerous cells, and yellow means equal expression.

Answer 1

In a comparative microarray experiment, cDNA from normal and cancerous cells is labelled with different fluorescent dyes — red for normal cells and green for cancerous cells — and hybridized to the microarray spots containing gene-specific probes. Interpretation of colors observed on the microarray:

• Red spots: Genes expressed more in normal cells than in cancerous cells (higher red fluorescence).
• Green spots: Genes expressed more in cancerous cells than in normal cells (higher green fluorescence).
• Yellow spots: Genes expressed equally in both normal and cancerous cells, resulting from the overlap of red and green signals.
• Black or no color: Genes not expressed or below detection level in both cell types.

Thus, the color pattern on the microarray helps identify genes that are upregulated, downregulated, or unchanged in cancerous cells compared to normal cells.