In the study of mutationmechanism, it was found in 6 cases that there were gains and losses of sites due to nucleotide substitution.
在研究突变机制时，发现有6例由于核苷酸的替换引起了限制性位点的增减。
2
The second mechanism is a more gradual process of adaptive mutation, whereby the capability of the virus to bind to human cells increases during subsequent infections of humans.
The new mathematical results allow calculation of this mechanism when the fitness function and the mutation, recombination and horizontal gene transfer rates are known.