Answer: Wednesday expresses the mutant allele while Morticia does not express it.
Step-by-step explanation:
The allele being present in both Wednesday and Morticia, have varying expressions phenotypically. It can easily be told, looking at Wednesday's feet that she carries the allele for a longer second toe while looking at Morticia, one could assume she doesn't carry the mutant allele. However, genotypically, she is a carrier just as Wednesday is.