While DNA Microarrays Can Be Used to Determine Whether or Not

question 62

Multiple Choice

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.
-In a muscle cell, the contractile protein myosin is present in larger quantities than the structural protein actin. Which of the following qPCR results would support this observation?

• A) The fluorescent signal for myosin is higher than that of actin.
• B) The fluorescent signal for actin is higher than that of myosin.
• C) The fluorescent signals for myosin and actin are equal.
• D) The fluorescent signal for myosin is large and is zero for actin.

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