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What is a DNA probe? A DNA probe is a short, single-stranded segment of DNA that is complementary to a specific DNA sequence or allele - AQA - A-Level Biology - Question 8 - 2019 - Paper 1
Question 8
What is a DNA probe? A DNA probe is a short, single-stranded segment of DNA that is complementary to a specific DNA sequence or allele. It is used to detect the pre... show full transcript
Worked Solution & Example Answer:What is a DNA probe? A DNA probe is a short, single-stranded segment of DNA that is complementary to a specific DNA sequence or allele - AQA - A-Level Biology - Question 8 - 2019 - Paper 1
Step 1
Describe how the DNA is broken down into smaller fragments.
Answer
The DNA is broken down into smaller fragments by the action of restriction endonucleases, which are enzymes that cut the DNA at specific recognition sites. This enzymatic action produces various-sized DNA fragments that are suitable for later separation and analysis.
Step 2
The DNA on the nylon membrane is treated to form single strands. Explain why.
Answer
The DNA on the nylon membrane is treated to form single strands to allow the DNA probes to bind effectively. Single strands provide accessible complementary sequences for the probes, facilitating the detection of specific DNA sequences.
Step 3
Suggest and explain how the sizes of the different viral fragments were determined.
Answer
The sizes of the different viral fragments were determined by comparing the viral DNA fragments to a standard lane that contains DNA fragments of known sizes. By running electrophoresis, the distance each fragment travels can be measured, allowing for size estimation based on their relative positions.
Step 4
Which volunteers had at least one of the viral DNA fragments with 250 base pairs or 535 base pairs?
Answer
Volunteers 3, 4, and 5 had at least one of the viral DNA fragments with either 250 base pairs or 535 base pairs. This information can be deduced as their sample results matched the respective sizes.