One way is to use Value Labels, a column property. It is easy to do manually for a limited number of values, but can also be done with JSL.
For example:
dt = Current Data Table();
// Make list of value label "assignments"
vl = Repeat(
i = 0;
{i++ ; Eval Expr(Expr((:DNA2[i])) = Expr(Char(:DNA1[i]) || Char(:DNA2[i])))};,
N Row(dt)
);
// Set value label property
:DNA2 << Value Labels(vl);
// Make chart
dt << Chart(X(:Batch), Y(:DNA2), Label by Value, Show Labels, Bar Chart(1));