Acell contains two sets of dna. if the gene on one molecule
ofdna has a mutation, how will that affect the gene on the
othermolecule of dna?

The DNA is the genetic material of almost all the living organisms and perform the important functions of the cell. Any mutation in DNA can be lethal for the organisms.

The cells that has the two sets of the DNA, they might be identical. The mutation in one gene can be sensed by the other DNA as well. The normal DNA will able to perform the function of the mutated DNA. In case of the silent mutation, the functioning of the DNA will not get affected.