NATS 1690 Lecture Notes - Phenotypic Trait, Pigment, Intellectual Disability
4 Nov 2013
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Document Summary
When a single gene influences multiple phenotypic traits. When a gene codes for a product that is used by various cells, or has a signaling function on various targets. Caused by a deficiency of the enzyme phenylalanine hydroxylase, which converts the essential amino acid phenylalanine to tyrosine. Without the enzyme, levels of phenylalanine and two closely related substances build up in the body. These substances are harmful to the central nervous system and cause brain damage. Phenylalanine is required for production of pigment melanin. When two or more genes govern the same phenotypic trait. The effects of 2 or more genes may be additive on a single phenotypic character in an individual. Controlled by 3 different genes at 3 different loci on 3 different chromosomes. Each of the 3 genes has two alleles (one light and one dark) The dominant alleles contribute to the color. Each of the contributing dominant alleles have additive effects on seed color.
