Exam review 2 - Bio 133 Multifactorial traits Feb 15, 2008...

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Bio 133 Feb 15, 2008 Multifactorial traits Variation Genes and Environment o Mendelian Traits: Due to a single trait Either/ or pattern of inheritance Pea plants (purple or white) Huntington’s Disease (Have it or not) o Multifactorial Trait: Traits that are influenced by the environment Heart Disease Intelligence Skin Color Height Weight o Polygenic traits: Due to activity of more than one gene Varies continuously Bell Curve distribution of phenotypes Empiric Risk Predictions of recurrence based on the trait’s incidence in a specifc population Incidence- Rate at which an event occurs o They base this on observations and epidemiological studies Heritability Percent of phenotypic variation due to genes o H=1 Genes only o H=o Environment only Correlation coefficient: Proportion of genes relative share Proportion of people sharing a trait compared to proportion predicted to share trait o Example 100 pairs of siblings Mendelian Trait: Expect in for 50 sibling pairs If trait is only observed in 37 pairs Heritability is .37/.50= .74 o Heritability id a component of Phenotype attributed to genes Its easy to determine heritability in animals and plants Its not so easy for humans Adoption Studies Adopted people share the environment but not the genes of their adoptive parents They share the genes but not the environment with their biological parent Twin Studies Provides better information that adoption studies
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Concordance: Percent of pairs in which both twins express the trait SNP (Single Nucleotide ) Nucleotide with more that one allele is a polymorphism Site is polymorphic if allele is present in more that 1% of the population o On average between two random individuals, there is one SNP in every 100 bases o 3 Million differences Association Studies Studies which compare groups of interest to control group for presence of SNP Controls are matched with age, ethnicity, Gender and Environment
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This note was uploaded on 03/30/2008 for the course BIOL 133 taught by Professor Cloud during the Spring '08 term at Pennsylvania State University, University Park.

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Exam review 2 - Bio 133 Multifactorial traits Feb 15, 2008...

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