Unformatted text preview: Complex Patterns of Inheritance
Chapter 5 Discontinuous or Continuous Phenotype Discontinuous variation = Continuous variation = Fig. 5.2 Continuous Variation in Humans Fig. 5.1 Terms Polygenic traits = Multifactorial traits = Complex traits = Polygenic Inheritance Phenotype due to two or more genes Range of phenotypes Better analyzed in populations than individuals Example: human eye color Loci = More loci = more Fig. 5.5 phenotypes Fewer differences between phenotypes Multifactorial Traits Genotype does not change except by... Phenotype can change throughout life Environment = genetic and nongenetic factors Polygenic (meaning) Genes act additively Characteristics of Multifactorial Traits Phenotype = genotype and environment Gene interactions may be unclear Phenotypic Variation
Two sources of phenotypic variation: Genotypes Environmental variation Heritability = Phenotypic Variation
Measured with correlation coefficients (r) If r = 1 high correlation If r = 0 low correlation Correlation does NOT equal causation! Twin Studies Monozygotic twins = Dizygotic twins = Concordance = Share how many of their genes? Share how many of their genes? Fig. 5.10 Survey of Multifactorial Traits Obesity Cardiovascular disease Skin Color Obesity Fig. 5.11 Twin studies 70% heritability Adoption studies 30% heritability Genes for Obesity Leptin = hormone helps control fat production Made by fat cells Mutations only account for ~5% of obesity Many genes control obesity Leptin Fig. 5.13 Risk Factors for Cardiovascular Disease Heredity Being male Hypertension High blood cholesterol Obesity Environmental factors: Smoking Lack of exercise Stress Genetic Disorders Associated with Cardiovascular Disease Angiotensinogen gene Familial hypercholesterolemia Autosomal dominant defective or absent LDL receptors Genetics of Skin Color ...
View Full Document
- Fall '07
- Genetics, Multifactorial traits, Survey of Multifactorial Traits