Question

A functional genomics experiment is carried out using a DNA microarray to characterize gene expression in cancer cells. First, control RNA is isolated from normal skin cells, reverse transcribed to DNA and labeled with green fluor. Then, RNA is isolated from a melanoma (skin cancer tumor), reverse transcribed, and labeled with red fluor. The samples are mixed and hybridized to the microarray.

What can you conclude about the behavior in tumor cells for any particular gene (spot on the microarray) that fluoresces:

red:

yellow:

green:

Answer 1

The microarray analysis depends on the hybridization of the probes. The complementary nucleotides pair with other by hydrogen bonds. Thus, it is used to know the gene expression level with the help of short sequences called probes.

Red: The red spots indicate that the corresponding gene is highly expressed in the melanoma cancer cells compared to the expression in control.

Yellow: The gene in this case is neither strongly repressed, nor strongly expressed. This shows that the gene expression is equal to the reference sample. In this case, it is cDNA synthesized from normal skin cells.

Green: The green spots depict that the gene was repressed in the cancer cells. Thus, showing lesser expression as compared to the control.