RNA6B model (Tillier, 94)

The RNA6B model (Tillier, 1994) is formed by restriction of the RNA6A model. The RNA6B model has only 3 rate parameters and 6 frequencies, it uses a rate of single transitions $\alpha_1$ and a rate of double transversions $\alpha_2$. The reference for the rate ratios are the rates of double transition. The transition rate matrix is given in table 2.7.

Table 2.7: RNA6B transition matrix