Best primers for the PCR reaction?

Question

The best primers for the PCR reaction have the following feature:

a) They have a high G-C content.

b) They have a high A-T content.

c) They should be palindromic.

d) The AT/GC ratio does not matter.

e) They should anneal rapidly, before the larger DNA strands reanneal.

Answer 1

The answer is e.  You want the primers to anneal to the single-stranded DNA template and don't want the template to re-anneal to itself.  As for the other answers, here is why they are incorrect:

Answers a, b and d:  The AT/GC content matters and the GC content should generally if at all possible be 40%-60% (thus meaning that the AT content conversely should be 60%-40%).  The GC content should not be high (and thus the AT content should not be low and vice versa).

Answer c:  If the primers are palindromes then they would very likely simply anneal to themselves and no priming would occur.

Answer 2

e) They should anneal rapidly, before the larger DNA strands reanneal.