Hi @Earendur ,
If you use the Mut 1 and Mut 2 columns, JMP will never put them in the same graph for the ANOVA analysis. You could however graph them together in Graph Builder. It'll group them, but nest the X-axis in a nice graphical way, but doesn't really do much for a proper analysis that you might be after.
DiedrichSchmidt_0-1613680301681.png
JMP treats the "A, B", "A, D", and "G, I" mutations as a single "factor" if you do a one-way with the Mut and Y columns. If certain mutations always occur as specific pairs (like with DNA pairs), then you would not want to split out the mutations into separate columns (I'd think), as the unique pairing is what is special, not each one individually so much.
JMP is doing the right thing in each case. A one-way/ANOVA might not be the right analysis you're after either -- you might be better off with a logistic analysis or doing a least squares fit to the data. (I added more rows by copy/pasting the Mut column at the end of the table.)
DiedrichSchmidt_1-1613681080996.png
A lot of this comes back to what @ron_horne was saying about how to structure your data for the right kind of analysis that you are trying to do.
Hope this helps!,
DS