| A | B |
|---|
| DNA | macromolecule; condenses around histones to create chromosomes |
| chromosome | a unit of DNA wound around histone proteins |
| homologous | members of a pair of chromosomes; hold same genes but not necessarily the same trait for which the gene codes |
| allele | alternate forms of a gene at a given loci; ex. B or b |
| homozygous | when the alleles for a given gene are the same; ex. BB or bb |
| genotype | actual alleles for a given gene |
| phenotype | the expressed trait determined by the pair of alleles for a gene |
| dominant | the allele that is expressed in a heterozygous situation |
| recessive | the allele that is not expressed in a heterozygous situation |
| autosome | any chromosome of the first through twenty-second pairs |
| sex chromosome | the 23rd pair of chromosomes |
| heterozygous | when the alleles for a given gene are the same; ex. Bb |
| autosomal recessive | a condition that presents itself only when both recessive genes are present and located on an autosome (ex. cystic fibrosis, tay-sachs) |
| autosomal dominant | a condition that presents itself when a dominant gene is present and located on an autosome (ex. Huntington's, Marfan's) |
| sex-linked | a condition whose genes are located on the sex chromosomes (probably the X); expressed more frequently in males |
| gene | a unit of DNA that codes for a trait |
