BIOL 190 Lecture Notes - Lecture 20: Phenylketonuria, Intellectual Disability, Diabetes Mellitus Type 2
Document Summary
A characteristic is determined by 2 or more genes. Examples- eye color, height, skin color: epistasis. One gene affects the expression of another gene, resulting in unique phenotypes: pleiotropy. One gene controls several apparently unrelated characteristics. All forms of albinism are associated with vision problems: environmental effects on gene expression and inheritance. Phenotypes can be affected by the environment in which the gene is expressed. Lack an enzyme that converts the amino acid phe into tyr. If identified at birth- can have a normal phenotype with a simple environmental (dietary) change- no phe in diet. A gene is located on a sex chromosome females - have two copies of x (xx) Males have one x and one y (xy) Males only have one copy- no backup allele.
