| Term | Definition |
| Punnett square | A chart that can be used to determine the possible outcomes for the offspring between two parents |
| Homozygous | Both alleles for a gene are the same; trait is always seen |
| Heterozygous | Two alleles for a gene are different; one allele is usually dominant and this one is expressed; the recessive allele is not expressed |
| Genotype | The genetic make-up of a person |
| Phenotype | Physical characteristics of an organism due to the genes that it has |
| Autosomes | All non-sex chromosomes |
| Sex chromosomes | 23 pair that determines sex; females have two X chromosomes, males have one X and one Y chromosome |
| Dominance/recessive inheritance | Based on interaction of dominant and recessive alleles |
| Dominant alleles | Traits that include: A. tongue rolling B. widow's peak C. Free (unattached) ear lobe D. interlocking fingers with left thumb on top E. hair on middle segment of finger F. Straight thumb (not "hitchhickers") |
| Huntington's disease | A genetic disorder caused by a dominant alle; caused by a delayed action gene not expressed until age 30 or 40; symptoms are fatal and include mental deterioration, uncontrolled movements, loss of intellectual faculties, and emotional disturbance |
| Cystic fibrosis | Genetic disorder caused by recessive alleles; symptoms include buildup of mucous in the lungs; 1 in 3,500 |
| Phenylketonuria | Caused by recessive alleles; inability to break down phenylalanine - leads to poor mental development |