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One way to detect and measure accurately the amount of RNA in a tissue sample is by RT-PCR (reverse transcriptase-polymerase chain reaction) - AQA - A-Level Biology - Question 8 - 2017 - Paper 1
Question 8
One way to detect and measure accurately the amount of RNA in a tissue sample is by RT-PCR (reverse transcriptase-polymerase chain reaction). RT-PCR uses a reaction... show full transcript
Worked Solution & Example Answer:One way to detect and measure accurately the amount of RNA in a tissue sample is by RT-PCR (reverse transcriptase-polymerase chain reaction) - AQA - A-Level Biology - Question 8 - 2017 - Paper 1
Step 1
Explain the role of reverse transcriptase in RT-PCR.
Answer
Reverse transcriptase is an enzyme that synthesizes complementary DNA (cDNA) from the messenger RNA (mRNA) template. This process is essential for the RT-PCR technique, as it allows the initial RNA to be converted into a DNA form that can be amplified through the PCR process.
Step 2
Explain the role of DNA polymerase in RT-PCR.
Answer
DNA polymerase is responsible for joining nucleotides to form complementary strands of DNA during the PCR amplification process. It facilitates the replication of DNA by adding nucleotides to the growing DNA strand based on the template provided.
Step 3
Explain why any DNA in the sample is hydrolyzed by enzymes before the sample is added to the reaction mixture.
Answer
The DNA in the sample is hydrolyzed prior to the reaction mixture addition to ensure that it does not interfere with the RT-PCR process. This removal is crucial because any pre-existing DNA could potentially act as a template, skewing results and leading to inaccurate measurements of the RNA content.
Step 4
Use this information to calculate the ratio for RNA content in sample A : RNA content in sample B.
Answer
From the graph, if it is determined that the number of cycles required to reach 50% maximum concentration of DNA for samples A and B are 20 and 30, respectively, the calculation for the RNA content would be as follows:
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Calculate C values: For sample A, C is 20, and for sample B, C is 30.
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Thus, the ratios can be calculated as:
- Sample A: ( \frac{1}{C_A} = \frac{1}{20} )
- Sample B: ( \frac{1}{C_B} = \frac{1}{30} )
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Therefore, the ratio for RNA content in sample A : RNA content in sample B is ( \frac{1/20}{1/30} = \frac{30}{20} = 1.5:1 ).