Designing primers
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This needs more work, but wanted to get it started.
General Rules
- Avoid runs over 3 nucleotide (AAAA)
- 18-30bp in length. Molecular Cloning says that 5' tails do not significantly affect annealing.
- Primer pairs should differ in length by less than 3bp.
- 3’ end should be G or C (stronger bond)
- Primer melting temp (Tm) should be 50-60C w/ low FIR difference (<5C, 2C better)
- Molecular Cloning advises GC content between 40% and 60%
- Avoid palindromes and inverted repeat sequences.
- Avoid complementarity between members of a primer pair.
- Check for dimer binding and hairpins in Vector NTI.
- Want to avoid structures with ΔG < -5kcal/mol
Useful Primer Design Tools
- VectorNTI
- Invitrogen
- Primer3
- Austin's clipboard tool - online tool for generating the complement, reverse complement and restriction enzyme site analysis of a DNA sequence. It also translates the sequence and gives the amino acids properties.
