8.1: Human Genetics - Terms and Concepts
| Chromosome | One of 46 strands of DNA in a human nucleus. |
| Gene | A unit of heredity located on a chromosome. Example: eye color gene |
| Allele | An alternate form of a gene. Example: blue eyes |
| Homologous Chromosome | Homologous chromosomes contain the same genes at the same location; however, the alleles may differ. |
| Dominant allele | The dominant allele masks the recessive allele. Example: people with dominant allele, B, make brown eye pigment. Both genotypes BB and Bb give brown eyes. Use an uppercase letter for the dominant allele. |
| Recessive allele | The recessive allele is masked by the dominant allele. People bb have blue eyes. Use a lowercase letter for the recessive allele. |
| Homozygous | The two alleles on homologous chromosomes are the same Example: BB = two brown eye alleles bb = two blue eye alleles |
| Heterozygous | The alleles on homologous chromosomes are different. Ex: Bb |
| Genotype | The genetic makeup of an individual. Example: BB, Bb, or bb |
| Phenotype |
The appearance of the individual Ex: brown eyes, blood
type A |
| Punnett Square | Diagram used to illustrate transmission of traits through generations |
| Autosomes | Chromosome pairs 1 – 22 are not different in males and females |
| Sex Chromosomes | Sex chromosome pairs are shown last in the karyotype. Females possess 2 large X chromosomes while males possess one X chromosome and a smaller Y chromosome. |