Question

what are advantages and disadvantages of primers using long length

Answer 1

Explanation:

The possible reasons behind choosing primer length exceeding 30 base pairs could be:

1) Mispairing of primer to site other than target site.

2) Forward primer might anneal to the strand of reverse primer, if more than 4-5 base are exactly same in the sequence forming primer dimer.

(It is therefore advised to avoid repetitive long repeats of bases while designing primer)

3) Primer might also bend and pair with the bases in the same strand forming hairpin loop structure.

Any of the above reasons could decrease the efficiency of your PCR !

Answer 2

Answer:

The short length primers bind more efficiently to the targeted DNA, but lacks specificity. Whereas the long length primers shows greater specificity when it comes to binding of enzymes to the primers or differentiating the process of DNA replication between close species.