How many copies could PCR make if we started with one copy of a template and performed 15 cycles of copying? a. A few b. A few hundred c. A few thousand d. Millions

Hi, everybody. Next question says, if you start with 10 copies of a DNA template and perform 10 cycles of PC R, how many copies of the target DNA sequence would you expect to have at the end? A 10 B 100 C 1024 or D 10,240. So we have a formula for this. But let's just think briefly as a gut level check what is going on in terms of how you're amplifying the DNA and PC R, we recall that for each cycle of PC R, we break apart our two DNA strands, once they're separated the primers anneal to each strand and a new strand is synthesized extending from the primer. So that at the end of one cycle, you have two copies of the original DNA. Now imagine in the second cycle, the second, the same thing will happen except you're starting with two copies. Each of those two copies, you'll end up with two copies of those. So at each cycle of PC R, the number of DNA copies doubles, meaning we have exponential growth of the number of copies, which is precisely why PC R is such a powerful technique for DNA amplification. So with that in mind, that leads us to our formula which says that the number of copies at the end equals the initial number of copies multiplied by two to the nth power where N is the number of PCR cycles. So let's fill in those numbers. The number, initial number of copies we have are 1010 copies of the initial DNA template multiplied by two and then we have 10 cycles of PC R. So two to the 10th power that will equal 10 multiplied by 1024 which will equal 10,240. So you can see that's the very highest number here. Choice D choice C 1024 is incorrect because it doesn't account for the fact that we had 10 copies to start with and then choice A 10 and B 100 much too low. Given that we're looking for an exponential growth in the number of copies. So once again, starting with 10 copies and performing 10 cycles of PC R, we expect choice D 10,240 copies of our DNA sequence at the end. See you in the next video.