Question

1a) If the PCR begins with 1 nanogram of target DNA, calculate how many grams of DNA would be present after 10 cycles of PCR.

1b) About how many DNA copies were made from the original DNA target if it were to go through 10 cycles of PCR. Answer in scientific notation.

Answer 1

1a) the PCR progress geometrically.

if we are starting with x amount of DNA

x, 2x, 4x, 8x....

this is like 1,2,4,8,16,32,64,128,256,512,1024

so after 10 cycles the amount of DNA=1024x

so amount of DNA after 10 cycles= 11024=1024 nanogram.

1b) If the PCR starts with 1 DNA molecule

the PCR progress as

1,2,4,8.....

this follows a geometric progression, the r=nth term/n-1 th term=4/2=2

number of DNA molecules after n cycles= n+1 th term

in a geometric progression n+1 th term = ar^n+1-1=ar^n

a is the first term, a=1

number of DNA molecules after 10 cycles= 12^10=1024

so the number of DNA molecules after 10 cycles of PCR if we are starting with 1 molecule of DNA = 1024=1.02410^3