Factors that may effect variables are called

independent variables (IV): These are the factors or conditions that you manipulate in an experiment. Your hypothesis is that this variable causes a direct effect on the dependent variable.

Dependent variables (DV): These are the factor that you observe or measure.

small, big, or no change could occur in the phenotype. it could cause something as simple as a cats ears to curl backwards or something as frighting as death. it could also occur in the protien-coding area and have an effect on that but no effect on the amino acids. what has to occur is a changing in the hox gene or the control gene.