A PCR starts with one molecule of the target…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A PCR starts with one molecule of the target.
- How many millions of copies are there after 30 cycles, if every molecule is copied in every cycle?
- How many millions of copies are there after 30 cycles at an efficiency of 90 per cent?
- At least how many cycles are needed to make a million copies, with a perfect doubling?
- How many double strands with exactly the length of the target are there after 6 cycles of perfect doubling?
Need a reminder? The key ideaShow
In a gel, the size of a fragment falls in a straight line against the distance on a log scale. A ring cut at sites gives pieces, and a straight DNA gives . In PCR, copies are made from one molecule in cycles. The Wallace rule is in degrees Celsius.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. One molecule, 30 cycles.
Plan. Use , and .
Step 1. (a) , which is million.
Step 2. (b) , which is million.
Step 3. (c) is too small. is enough. So 20 cycles.
Step 4. (d) .
Answer: million; million; ; .
Check. The loss of 10 per cent in each cycle cuts the result by a factor of about 5, because .
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