Bio221 Exam 4

Bio221 Exam 4 - Bio 221 Evolution Exam 4 2 Major Challenges...

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Bio 221 Exam 4 Evolution 2 Major Challenges o o Conserved Common Design Evolutionary change in genes regulating development Evolution from fish to land animals (Devonian) o Proximal limbs homologous to tetrapod o Distal elements not homologous to tetrapod Evolution of Digits Caused by new distal pattern of Hox gene expression late in limb development Signaling of FGF & SHH in fish stopped early causing lack of distal bones & excess ectodermal tissue o Hoxa-11: Develops carpal bones o Hoxd-13: Formation of asymmetric digits Morphological Diversity of Limbs Experiment of Hampé on chicks o Normal chicks stop signaling early causing inhibited growth of fibula and fusion of ankle o Embryonic inhibition of inductive signal Reduction of Vertebrate Limbs o Late/Distal elements lost first o Nature Nurture Important Definitions Population: Interbreeding group of individuals Effective Population Size: # breeding individuals (N e ) Gene Pool: All alleles in a population Polymorphic Locus: A gene locus with two or more alleles Allele Frequency: Relative frequency of a particular allele (proportion 0-1) Genotype Frequency: Relative frequency of a particular genotype (proportion 0-1) Evolution: Genetic change in a population over time
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Quantitative Genetics Quantitative traits: continuously variable (height/seed production) Variations in quantitative traits resemble bell-shaped curve = normal distribution Characteristics: o Polygenic o o Phenotypic variation = Genetic variation + Environmental variation Heritability: Proportion of total phenotypic variation (v p ) due to genetic variation (v g ) h 2 = v g /(v g + v e ) where h 2 varies 0 – 1 (all or none of phenotype is due to genetics) h 2 Artificial Selection: o o Offspring/parents = realized heritability Depends on environment in which it is measured Measuring Genetic Variability
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This note was uploaded on 04/29/2008 for the course BIO 221 taught by Professor Welsh during the Spring '08 term at Allegheny.

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Bio221 Exam 4 - Bio 221 Evolution Exam 4 2 Major Challenges...

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