Final answer:
Epistatic genes are involved in interactions that can mask or modify the expression of other genes, often within gene pathways, affecting phenotype. On the other hand, pleiotropic genes have the ability to influence multiple phenotypic traits from a single gene. Both concepts illustrate the complexity of genetic influence beyond simple Mendelian inheritance.
Step-by-step explanation:
The differences and similarities between epistatic genes and pleiotropic genes center on how these genes interact within an organism's genome to influence phenotypes. Epistatic genes are involved in interactions where one gene's expression may mask or modify the expression of another, leading to phenomena where the effect of one gene is dependent on the presence of another. This is commonly seen in genetic pathways where genes work in a sequence to produce an effect. An example is how multiple genes contribute to eye color in humans, and how some genes can mask the effect of others in this process. On the other hand, pleiotropy describes the ability of a single gene to affect multiple phenotypic traits. Such a gene has multiple, sometimes unrelated, effects on the phenotype. This means that one gene can contribute to several characteristics, which can be quite distinct from each other.
Both pleiotropy and epistasis illustrate the complexity of genetic relationships and challenge the simpler Mendelian concept wherein each trait is controlled by a single gene. In summary, the key similarity is that both involve genes that affect phenotypes in more than a straightforward, single-trait manner. However, they differ in their mechanisms: epistasis involves interactions between different genes, while pleiotropy involves multiple effects of a single gene.