Mutational Signatures (v3.1 - June 2020)

Doublet Base Substitution (DBS) Signatures

Doublet base substitutions (DBS) are generated after the concurrent modification of two consecutive nucleotide bases. There are 78 strand-agnostic DBS mutation types, enumerated here.

More specifically, there are 16 possible source doublet bases (4 x 4). Of these, AT, TA, CG, and GC are their own reverse complement. The remaining 12 can be represented as 6 possible strand-agnostic doublets. Thus, there are 4+6=10 source doublet bases. Because they are their own reverse complements, AT, TA, CG, and GC can each be substituted by only 6 doublets. For the remaining doublets, there are 9 possible DBS mutation types (3 x 3). Therefore, in total there are 4 x 6 + 6 x 9 = 78 strand -agnostic DBS mutation types.

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