| A | B |
|---|
| trait | A characteristic that an organism can pass on to its offspring through its genes. |
| heredity | The passing of traits from parents to offspring |
| genetics | The scientific study of heredity. |
| purebred | An organism that always produces offspring with the same form of a trait as the parent. |
| gene | A segment of DNA on a chromosome that codes for a specific trait. |
| alleles | The different forms of a gene. |
| dominant allele | An allele whose trait always shows up in the organism when the allele is present. |
| recessive allele | An allele that is masked when a dominant allele is present. |
| hybrid | An organism that has two different alleles for a trait; an organism that is heterozygous for a particular trait. |
| probability | The likelihood that a particular event will occur. |
| punnett square | A chart that shows all the possible combinations of alleles that can result from a genetic cross. |
| phenotype | An organism’s physical appearance, or visible traits. |
| genotype | An organism’s genetic makeup, or allele combinations. |
| homozygous | Having two identical alleles for a trait. |
| heterozygous | Having two different alleles for a trait. |
| codominance | A condition in which neither of two alleles of a gene is dominant or recessive. |
| sperm | A male sex cell. |
| egg | A female sex cell. |
| meiosis | The process that occurs in sex cells (sperm and egg) by which the number of chromosomes is reduced by half. |
| mutation | A change in a gene or chromosome. |
| sex-linked gene | A gene that is carried on the X or Y chromosome. |
| carrier | A person who has one recessive allele for a trait and one dominant allele, but does not have the trait |
| pedigree | A chart or “family tree” that tracks which members of a family have a particular trait. |
| genetic disorder | An abnormal condition that a person inherits through genes or chromosomes. |
| selective breeding | The process of selecting a few organisms with desired traits to serve as parents of the next generation |
| clone | An organism that is genetically identical to the organism from which it was produced. |
| gene therapy | The insertion of working copies of a gene into the cells of a person with a genetic disorder in an attempt to correct the disorder. |
| genome | All of the DNA in one cell of an organism. |
