Question

If the initial number of template DNA molecules in a PCR reaction is 1000. What would be the number of product DNA molecules at the end of the 20 cycles closest to?

• A. A) 10
• B. B) 101010101010
• C. C) 101010101010101010
• D. D) 101010101010101010101010

Answer 1

The correct option is B B) 101010101010

Each DNA multiplies in exponents of 2.

Number of C-DNA after n cycles of PCR ( if started from 1 double-stranded DNA )= 2${}^n$

Thus, for 20 cycles each DNA yields 2${}^2$${}^0$ copies.

Thus for 1000 DNA templates, we will have ,

1000 x 2${}^2$${}^0$= 1000 x 1048576 = 10.5 x 10^8 copies at the end of 20 cycles.

So, closest considering is option B i.e., '101010101010'.