| Term | Definition |
| Incomplete dominance | Neither of the two allele is dominant over the other; e.g. RR-red, rr-white, Rr-pink |
| Sickle cell anemia | Disease that produces an abnormal form of hemoglobin; sickle-shaped; an example of incomplete dominance |
| Multiple allele inheritance | When a gene has more than two alleles; e.g. blood type A, B, and O (3 alleles); four possible phenotypes AB, A, B, O |
| Polygenic inheritance | Whena trait is controlled by more than one gene; e.g. eye, skin, hair color, height, metabolic rate |
| Sex-linked traits | Some genes found only in x-chromosomes; e.g. color blindness, hemophilia |
| Hemophilia | Failure of blood to clot; lacks clotting factors |