The probability of a switch from AT to GC is 0.002, while a switch from GC to

Question:

The probability of a switch from AT to GC is 0.002, while a switch from GC to AT occurs with probability 0.001.
In DNA, there are four nucleotides: A, T, C, and G. A pairs with T, and C pairs with G. In many organisms, mutations that change an AT pair into a GC pair are more common than those that change a GC pair into an AT pair. Write down Markov chains describing the above situation.