This chapter explains the basics of human chromosomal inheritance, including genes and alleles, genotypes and phenotypes, and dominant and recessive trait inheritance, polygenic inheritance, and disorders associated with genetic variations. Sex-linked (and sex-influenced) qualities and abnormalities are explained. Various autosomal dominant and autosomal recessive disorders are discussed, including Marfan Syndrome, Neurofibromatosis, Huntington’s Disease, cystic fibrosis (CF), Tay Sachs Disease, and albinism. Modern research on epigenetics (indicating effects of the environment on which genes are active or inactive within an individual) is also mentioned, including how trauma and lifestyle can affect individual and offspring genetic outcomes.