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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
1. Explain the role of reverse transcriptase in RT-PCR.
Answer
Reverse transcriptase catalyzes the synthesis of complementary DNA (cDNA) from messenger RNA (mRNA) in the reaction mixture. This process is crucial as it converts the RNA template into a stable DNA form that can be amplified during PCR.
Step 2
Step 3
3. Any DNA in the sample is hydrolyzed by enzymes before the sample is added to the reaction mixture. Explain why.
Answer
DNA must be removed to prevent it from being amplified during the PCR process. If present, this DNA could outcompete the RNA template during cDNA synthesis and produce inaccurate results in the quantification of RNA.
Step 4
4. Use this information to calculate the ratio for RNA content in sample A : RNA content in sample B.
Answer
From the graph in Figure 9, to find C for both samples, we determine the number of cycles needed to reach 50% of maximum fluorescence.
- For Sample A, C is approximately 1.5 cycles.
- For Sample B, C is approximately 1.0 cycles.
Thus, the ratio for RNA content in sample A to sample B can be calculated as: