Pleiotropy

pleiotropy

mutation in one gene that causes a disease with a wide range of symptoms, phenomenon in which a single gene contribution to multiple phenotypic traits

pleiotropic genes

genes that affect multiple, apparently unrelated, phenotypes

single gene may be involved in many pathways

tyrosine, needed for protein synthesis and is a precursoe for several NT, hormone thyroxine, and melanin
mutations in any one of the genes that affect tyrosine synthesis or metabolism may affect multiple body systems

indirect or secondary pleiotropy

single gene that effects widespread phenotypic effects

pigmentation and deafness

Waardenburg syndrome
gene is pleiotropic because the genes responsible for both the pigmentation and deafness phenotype
mutations of PAX3, encodes a transcription factor involved in neural crest dev.

antagonistic pleiotropy

the expression of a single gene causes competing effects, some of which are detrimental to the fitness of an organism
while some genes increase fitness early in life, they decrease fitness later in life
because the gene's harmful effects appear after repr

p53, antagonistic pleiotropy

gene directs damaged cells to stop reproducing, resulting in cell death, gene helps avert cancer by preventing cells with DNA damage from dividing, but can also suppress the division of stem cells, which allow the body to renew and replace deteriorating t

antagonistic pleiotropy can be a tradeoff between beneficial and detrimental effects

aging in drosophila evolved in response to damaging effects of reproduction earlier in life
flies with high fecundity earlier in life had decreased lifespan

Marfan Syndrome

FBN1 is responsible for a constellation of symptoms, including thinness, joint hypermobility, limb elongation, lens dislocation, and increased susceptibility to heart disease

Holt-Oram Syndrome

mutation in the gene that codes for transcription factor TBX5 cause cardiac and limb defects

Nijmegen breakage syndrome

mutation in the gene that codes for DNA damage repair protein NBS1 leads to microcephaly, immunodeficiency, and cancer predisposition

PKU

deficiency of pheynylalanine hydroxylase, that convert phenylalainine to tyrosine
defect in single gene that codes for enzyme causes multiple phenotypes, including mental retardation, eczema, and pigment defects, those affected, have lighter skin