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NATS 1690 (39)


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York University
Natural Science
NATS 1690
Barbara Czaban

Pleiotropy - 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  Sickle-cell disease - Example: Phenylketonuria (PKU)  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 - Multiple phenotypes associated with PKU  Mental retardation  Seizures  Tremors  Eczema  Pigment defects Polygenic inheritance - 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 - Example – Wheat seed color  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)  6 alleles are involved  The do
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