Question

You design a microarray experiment to determine the difference in gene expression patterns between normal and cancerous lung tissue from humans. You label the cDNA derived from a lung tumor with a red fluorescent dye and the cDNA derived from normal lung tissue with a green fluorescent dye. You hybridize the cDNA to a microarray chip in which each spot corresponds to a DNA sequence from a different human gene.

a. What can you infer about a particular gene’s expression if it’s corresponding spot fluoresces:

Green?

Red?

Yellow?

Black (no fluorescent signal)?

b. If you were searching for an anticancer drug that would inactivate a protein whose activity contributes to cancer, which of the genes represented on the microarray encode proteins you would most likely chose as a potential target? Green, Red, Yellow, or Black? Briefly explain.

Answer 1

Answer:-

According to the above question, In order to determine the difference in gene expression patterns between normal and cancerous lung tissue from humans by microarray experiment. The cDNA which is being labelled is basically coded mRNA from normal and abnormal lung tissue. cDNA from lung tumor is labelled with red fluorescent dye and DNA from normal lung tissue is labelled with green fluorescent dye. The the cDNA is subjected to the microarray, where binding of cDNA with its complementary base pairs on each spot takes place. After hybridization, scanning is done with the help of laser in order to see visible results.

(a) (1) If there's a Green fluorscence of a particular gene's expression that means the gene is highly repressed and is not expressed in cancer cells. It may be possible that the gene is playing role in inhibiting cancer.

(2) If there's a Red fluorescence of a particular gene's expression that means the gene is highly expressed in cancer cells and not expressed in the normal cells of human. This gene is responsible for causing cancer.

(3) If a spot appears with yellow fluorescence that means it has both red and green cDNA which are bound at the same spot. This gene is not strongly expressed nor strongly repressed in normal and cancerous cell of human. This gene is not involved in causing cancer.

(4) If there's a black spot which means that there is no binding of cDNA takes place with correspond DNA in that particular spot which results that means in normal and cancerous cell, there is no such activated gene present. This gene is also not involved in cancer production.

(b) Based on the above information provided in (a), we can say that if we are searching an anticancer drug, that would inactivate a protein whose activity contributes to cancer, so the genes which are represented by the red spots would be chosen as potential target for the same. As the gene present in the red spot are strongly expressed in the cancerous cell and causing cancer by producing proteins that contributes to the cancer. The anticancer drug would help in inactivation of these proteins by inducing cytotoxic effects with various molecular targets.

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