| A | B |
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| True Breedings | If an organism has a certain characteristic that is always passed on to all of its offspring, we say that this organism bred true with respect to that characteristic. |
| Allele | One of a pair of genes that occupies the same position on homologous chromosomes. |
| Genotype | Two-letter set that represents the alleles an organism possesses for a certain trait. |
| Phenotype | The observable expression of an organism's genes. |
| Homozygous | A genotype in which both alleles are identical. |
| Heterozygous | A genotype with two different alleles. |
| Dominant Allele | An allele that will determine phenotype if even one is present in the genotype. |
| Recessive Allele | An allele that will not determine the phenotype unless the genotype is homozygous with that allele. |
| 1. | The traits of an organism are determined by its genes. |
| 2. | Each organism has two alleles that make up genotype of a given trait. |
| 3. | In sexual reproduction, each parent contributes ONLY ONE of its alleles to the offspring. |
| 4. | In each genotype, there is a dominant allele. If it exist in an organism, the phenotype is determined by that allele. |
| Pedigree | A diagram that follows a particular species' phenotype through several generations. |
| Monohybrid Cross | A cross between two indivisual concentrating on only one definable trait. |
| Dihybrid Cross | A cross between two indivisuals concentrating on two definable traits. |
| Autosomes | Chromosomes that do not determine the sex of an individual. |
| Sex Chromosomes | Chromosomes that determine the sex of an indivisual. |
| Autosomal Inheritance | Iheritance of a genetic trait not on a sex chromosome. |
| Genetic Disease Carrier | A person who is heterozygous in a recessive genetic disorder. |
| Sex-linked Iheritance | Inheritance of a genetic trait located on the sex chromosomes. |
| Mutation | A radical chemical change in one or more alleles. |
| Change In Chromosome Structure | A situation in which the chromosome loses or gains genes during meiosis. |
| Change In Chromosome Number | A situation in which abnormal cellular events in meiosis lead to either none of a particular chromosome in the gamete or more tha one chromosome in the gamete. |
