Variable expressivity - Variable expressivity Same genotype...

Variable expressivity
Same genotype but expressed a little bit different
Ex: Lobe Eye
Ex: Bar eye
: correlation of temperature and expression
Pleiotropy: gene causes a change
-Phenylketonuria
*The metabolic pathway of phenylalanine
Excess Phenylalanine turns into Tyrosine
Gene: inability to metabolize phenylalanine which gives a defect in myelin sheet which gives a
person mental retardation
Excess amounts of Tyrosine it gets converted to Acid and gets eliminated very quickly
Albinism: lack of pigmentation: Tyrosinase turns into Melanin
Melanin absorbs ultraviolent light
Environmental alteration;
-In some cases, altering the environment can cause phenotypes to change – Phenocopies
*Himalayan coat pattern in mice and rabbits
Dark fur conserves the heat of the appendages
Black fur associated with skin temperature
Altering the environment we can alter the phenotype
*Siamese cats
Gene-gene interactions

9:3:3:1- genes that are assorted independently
 Epistasis is the condition in which one gene can control whether another is expressed
 In general we refer to any condition controlled by two genes as being epistatic