When one slide of a gene masks the presence of the other allele what form can be seen in the phenotype?

When one allele masks the presence of another, the phenotype is typically determined by the dominant allele. This phenomenon is known as complete dominance, where the dominant allele's traits are expressed in the phenotype, while the recessive allele's traits are not visible. Consequently, individuals with at least one dominant allele will display the dominant phenotype, regardless of whether they are homozygous or heterozygous for that trait.