Why GC pairs more suitable than AT in creating primers?

[niel23]

Having more GC pairs in a primer means a greater Tm.

Likewise, I read that having more GC are more prone to errors in PCR.

However, the answer to this question, without explanation, says having more GC pairs is more suitable and when it flanks the 5' and 3' ends.

Thoughts?

Thank you!

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[theonlytycrane]

A - T has 2 H bonds and G - C has 3 H bonds. Remember this for pretty much every variation of these types of questions.

You want the primers to stick and 3 h-bonds is more stable than 2.