Question

Explain, using examples, how pleiotropy can constrain an evolutionary response to a new environmental challenge to an organism.

Answer 1

Phenylketonuria is an example for pleiotropy ,an inherent disorder that effects the level of phenylalanine in the human body.This not only effect humans ,but also animals such as chickens and laboratory house mice.Pleiotropic gene action can limit the rate of multivariate evolution when natural selection ,sexual selection or artificial selection on one trait favors one allele,while selection on other traits favors a different allele.some genee evolution is harmful to an organism.Genetic correlations and responses to selection most often exemplify pleitropy.Other examples are albinism,autism and schizophrenia,,sicle cell anemia,mafran syndrome etc.In above all situations evolutionary constraint refers to a situation in which mutation in genes shared among traits that are not directly exposed to selective challenge show a correlated response.such response is deletrous ,it may constraint the trait from evolving.We know that gene effects are inherent to alleles and thus invarient across genetic and environmental backgrounds.Evidence from some studies involving genetic effects on multiple traits ,observed across diffrent genetic backgrounds and environments,supports the genes effect on traits change.Cosequently pleiotropy also varie across backgrounds.