Polymerase chain reaction (PCR) is a technique used to amplify (copy) DNA. Suppo
ID: 853536 • Letter: P
Question
Polymerase chain reaction (PCR) is a technique used to amplify (copy) DNA. Suppose a single linear molecule of double stranded DNA (dsDNA) is amplified by PCR.
1. After one PCR cycle, how many molecules of dsDNA would there be?
2. After three PCR cycles, how many molecules of dsDNA would there be?
3. After 30 PCR cycles (a typical number of cycles), how many molecules of dsDNA would there be? Choices are 60, 120, 625, 900, ~34 million, ~1 billion.
4. Consider that in a typical PCR you do not start with "a single molecule" of template DNA, but rather something in the range of 25 nanomoles of template DNA. What does this tell you about the potential of PCR to amplify DNA? (Choose A or B)
A. PCR is an efficient technique with the potential to produce a large amount of DNA
B. PCR is an inefficient technique with the potential to produce a small amount of DNA
Hint: Template DNA is incubated with primers, nucleotides, and a thermostable polymerase in a buffer with Mg2 ions (required for polymerase activity). PCR reaction: There is an initial denaturation step at 95
Explanation / Answer
1. 2^1 = 2
2. 2^3 = 8
3. 2^30 = ~1 billion
4. A. PCR is an efficient technique with the potential to produce a large amount of DNA