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The genome of a small virus is depicted below, showing the positions of cutting sites (P and Q) for two restriction enzymes - VCE - SSCE Biology - Question 20 - 2008 - Paper 1
Question 20
The genome of a small virus is depicted below, showing the positions of cutting sites (P and Q) for two restriction enzymes. The length of DNA fragments obtained wh... show full transcript
Worked Solution & Example Answer:The genome of a small virus is depicted below, showing the positions of cutting sites (P and Q) for two restriction enzymes - VCE - SSCE Biology - Question 20 - 2008 - Paper 1
Step 1
If both EcoR1 and BamHI are used together on this viral DNA, the length of fragments obtained would be.
Answer
To determine the length of DNA fragments when both EcoR1 and BamHI are used together, we can analyze the lengths obtained from each enzyme.
From the table, EcoR1 at cutting site Q produces fragments of lengths 3 kB and 7 kB. BamHI at cutting site P produces fragments of lengths 8 kB and 2 kB.
When these enzymes act together, the possible lengths of the DNA fragments can be calculated by combining the lengths from each enzyme:
- EcoR1 (3 kB) + BamHI (8 kB) = 11 kB
- EcoR1 (3 kB) + BamHI (2 kB) = 5 kB
- EcoR1 (7 kB) + BamHI (8 kB) = 15 kB
- EcoR1 (7 kB) + BamHI (2 kB) = 9 kB
Thus, the possible lengths for the resulting fragments when both enzymes are used are: 3, 8, 2, where 8 kB obtained from BamHI stands alone. According to the marking scheme, the correct combination of lengths is presented in option D, which states: 3, 7, 2.