2’-deoxyInosine (dI)

2’-deoxyInosine is a naturally occurring nucleotide, which forms stable base pairs with all four deoxynucleotides in the DNA duplexes. Thus, inosine is also known as "universal" or "neutral" base. Hence, stability varies in the following order: dI:dC > dI:dA > dI:dG ~dI:dT. Due to integration of an inosine nucleotide to the sequence of a primer, the primers obtain "variable" bases. Incorporation of dI in primers (so called degenerate primers) allows simultaneous amplification of homologous sequences, for example, close strains, poor conserved regions, etc. While using degenerate primers in PCR, proof-reading DNA polymerases have been reported to fall off the DNA as soon as they meet wobble bases in the sequence of the primer [DOI: 10.1101/gr.2.4.346], so we recommend to use common Taq or Pfu DNA polymerases.