PCR primers

[dxu425]

---

Members don't see this ad.

Hi all, just a quick question about a mol bio technique. I understand the concept behind PCR and how it works, but I don't get why there are references to a 5' primer and a 3' primer, like say in experiments with yeast. I know each new DNA strand is elongated off the primer 5'-->3'. So which strand does the 5' primer anneal to and which strand does the 3' primer anneal to?

Thanks!

 

[Sterling Archer]

Hi all, just a quick question about a mol bio technique. I understand the concept behind PCR and how it works, but I don't get why there are references to a 5' primer and a 3' primer, like say in experiments with yeast. I know each new DNA strand is elongated off the primer 5'-->3'. So which strand does the 5' primer anneal to and which strand does the 3' primer anneal to?

Thanks!

When you're interested in replicating a gene, you need two primers. Both primers still prime in the 5'->3' direction, but in between your primers is your gene of interest so you have a primer "in front" of your gene (5' primer) and the other primer "at the end" of your gene (3' primer)

 

[dxu425]

Thanks for the reply! So the way you're describing it makes it seem like the DNA is single-stranded. For a double-stranded piece of DNA, doesn't each primer anneal to a separate strand and extend 5' to 3'? Which parent strand of DNA do you look at to determine which primer is in front and which primer is at the end? Thanks!

 

[Sterling Archer]

It's still double stranded. 5' and 3' primer conventions are based on your sense strand usually. Think of it more as a pair of primers, one in the forward direction and the other in the reverse direction.