After reading the paragraph below, answer the questions that follow.
While DNA microarrays can be used to determine whether or not a gene is expressed in a cell, quantitative polymerase chain reaction (qPCR) can be used to specifically quantify the extent of gene expression in cells and tissues. To perform qPCR, mRNA is extracted from cells and reverse transcribed to complementary DNA (cDNA). Using fluorescent DNA molecules that recognize specific gene sequences and DNA polymerase, copies of the gene sequence of interest are made. After the copies are made, a fluorescent detector measures the intensity of the fluorescent signal, which is proportional to the number of mRNA transcripts in the cell and corresponds to the level of gene expression in the cell.
A scientist hypothesizes that a new drug turns on a certain gene in a skin cell. Which of the following experiments would be the best to test her hypothesis?
◦ Use qPCR to measure the levels of gene expression in skin cells after exposure to the drug and then add another drug to turn off gene expression and use qPCR to measure the levels of expression.
◦ Use qPCR to measure the initial levels of gene expression in skin cells, treat skin cells with the drug and measure the levels of gene expression, and then compare the two measurements.
◦ Use qPCR to measure the initial levels of gene expression in muscle cells, treat skin cells with the drug and measure the levels of gene expression, and then compare the two measurements.
◦ Use qPCR to measure the levels of gene expression in skin cells after exposure to the drug.
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