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 2
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 2
Step 1
Explain the role of reverse transcriptase in RT-PCR.
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Answer
Reverse transcriptase is an enzyme that synthesizes complementary DNA (cDNA) from a template of messenger RNA (mRNA). This conversion is essential for amplifying RNA sequences in the RT-PCR process.
Step 2
Explain the role of DNA polymerase in RT-PCR.
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Answer
DNA polymerase is responsible for synthesizing new DNA strands by adding nucleotides to the growing cDNA during the PCR amplification process, thus allowing the exponential increase of DNA.
Step 3
Explain why any DNA in the sample is hydrolyzed by enzymes before the sample is added to the reaction mixture.
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Answer
DNA is hydrolyzed to prevent it from being amplified during RT-PCR, as the presence of DNA would compete with the target RNA for amplification and could lead to inaccurate results.
Step 4
Use this information to calculate the ratio for RNA content in sample A: RNA content in sample B.
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Answer
To calculate the ratio of RNA content, identify the cycle numbers where the fluorescence levels reach 50% of the maximum for samples A and B from Figure 9. Let's assume A required 15 cycles and B required 20 cycles. Thus, the RNA content ratio is calculated as:
Suggest one reason why DNA replication stops in the polymerase chain reaction.
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DNA replication stops due to a limited amount of primers or nucleotides, which become exhausted as the reaction progresses.
Step 6
Explain why the scientists produced a variety of primers for this procedure.
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Answer
The scientists produced a variety of primers to ensure specificity for different RNA viruses, allowing them to detect multiple viral targets in patients suffering from respiratory diseases.
