Gene: segment of DNA that controls design or structure of a trait/characteristic of the cell or organism. In the most multicellular organisms 2 copies of the segment of DNA, termed Alleles, interact to give the particular form of the trait as seen.
Autosomal Gene: Gene located on an autosomal chromosome which is any of the 22 human chromosomes (or 3 Drosophila chromosomes) other than the X or Y. Autosomal genes are never sex-linked.
Sex-linked Gene: Gene located in the unpaired region of the X chromosome or on the Y chromosome. These genes tend to be seen in males.
Mendelian Organism: Organism whose patterns of heredity follow Gregor Mendel's 3 laws and tend to give offspring in phenotypic ratios of 3:1, 1:1, 9:3:3:1, and 1:1:1:1
Mendel's Laws: Laws of Dominance, Law of Segregation of Genes, and Law of Independent Assortment of Genes. Note: Mendel was wrong in his final Law because he did not know about Linkage; it should have read the "Law of Independent Assortment of Chromosomes".
Codominance: Non-Mendelian condition in which there are 3 different alleles for a gene. 2 of these alleles are different dominant versions of the gene. Therefore the possibility of A/B exists giving an AB blood type.
Gene Pool: Total of all alleles for a particular gene in a population. Particular allele/mutation could be rare as in albinism or relatively common as in diabetes or cystic fibrosis.
Down's Syndrome: Partial triploid condition in humans where there are 3 copies of chromosome 21. Unfortunately there are many physical problems (heart, liver, kidney, brain, & facial) that are visible
Turner's Syndrome: Partial haploid condition in humans where there is no pair in the X chromosome (often termed XO). Various physical changes occur in the phenotype including webbing of the neck and sterility.
Klinefelter's Syndrome: Partial triploid...