I have some somatic SNP data for multiple tumour normal comparisons that I'm exploring in plots such as this

This plot shows the contribution each mutation in a given trinucleotide context makes to the total mutation load. For example I find 2155 somatic snvs across all samples, and 19 of these are `A>C`

transversions in a trinucleotide context of `AAA`

(top left of the plot), so this particular class of mutation contributes 0.009 (19/2155) of the total mutations.

As there are 12 possible mutation class `A>G, A>C, A>T, G>C, G>T, G>A, C>A, C>G, C>T, T>A, T>C, T>G`

and for each mutation class there are 16 (2^4) possible trinucleotides e.g. `A>G`

in an `AAA`

context, I have plotted these separately.

However, most papers I see discussing the mutational spectrum (e.g. figure; paper) only refer to the following nucleotide changes: `C>A, C>G, C>T, T>A, T>C, T>G`

. Why is this? This suggests that a `C>A`

is **directly** equivalent to the complementary `G>T`

? Is this really the case?

If so, should I simply lump `C>A`

and `G>T`

transversions together when plotting?