Concordance When both twins express the same trait

Chapter 5 Human Heredity by Michael Cummings © 2006 Brooks/Cole-Thomson Learning

Survey of Multifactorial Traits • Obesity • Cardiovascular disease • Skin Color • Intelligence

Obesity • Serious health concern • Twin studies estimate heritability close to 70% • Adoption studies estimate heritability around 30% Fig. 5. 11 Chapter 5 Human Heredity by Michael Cummings © 2006 Brooks/Cole-Thomson Learning

Obesity predisposes to higher risks of: Type II diabetes Hypertension Coronary heart disease Osteoarthritis Cancers Measured by BMI = weight (kg)/height (m)2 >30 BMI considered obese Chapter 5 Human Heredity by Michael Cummings © 2006 Brooks/Cole-Thomson Learning

ob/ob mouse Credit: © Dr. Daniel Eitzman/Visuals Unlimited Chapter 5 Human Heredity by Michael

Experiments with parabiotic mice Chapter 5 Human Heredity by Michael Cummings © 2006 Brooks/Cole-Thomson

ob - Leptin db - Leptin receptor Chapter 5 Human Heredity by Michael Cummings

Weight homeostasis Chapter 5 Human Heredity by Michael Cummings © 2006 Brooks/Cole-Thomson Learning

P=G+E Chapter 5 Human Heredity by Michael Cummings © 2006 Brooks/Cole-Thomson Learning

Genes for Obesity • Several identified genes in mice Weight controlling hormone leptin • Human genes – Gene for leptin maps to chromosome 1 p 31 – Mutations account for small percentage (~5%) of obesity cases – Important genes for obesity are located on numerous chromosomes Chapter 5 Human Heredity by Michael Cummings © 2006 Brooks/Cole-Thomson Learning

Gut flora affecting obesity? nature. com Chapter 5 Human Heredity by Michael Cummings ©

Gut flora affecting obesity? Bacteria digest complex polysaccharides Make more nutrients (i. e. more calories) available to host Lean mice/humans More Bacteroidetes , Less Firmicutes Obese mice/humans More Firmicutes, Less Bacteroidetes Inject gut flora from lean mice to obese mice - get leaner!!! Chapter 5 Human Heredity by Michael Cummings © 2006 Brooks/Cole-Thomson Learning

Risk Factors for Cardiovascular Disease – Heredity – Male – Hypertension – High LDL or low HDL – Smoking – Obesity – Lack of exercise – Stress http: //academic. brooklyn. cuny. edu/biology/bio 4 fv/page/ldl. gif Chapter 5 Human Heredity by Michael Cummings © 2006 Brooks/Cole-Thomson Learning

Genetic Disorders Associated with Cardiovascular Disease • Angiotensinogen gene • Familial hypercholesterolemia Autosomal dominant defective or absent LDL receptors • Numerous others Chapter 5 Human Heredity by Michael Cummings © 2006 Brooks/Cole-Thomson Learning

Atherosclerosis Credit: © Carolina Biological/Visuals Unlimited Chapter 5 Human Heredity by Michael Cummings ©

Skin color • Controlled by more than two genes Fig. 5. 18 Chapter 5

Skin Color Fig. 5. 19 Chapter 5 Human Heredity by Michael Cummings © 2006

Intelligence • Intelligence quotient (IQ) • Currently no objective way to quantify components of intelligence • IQ values are heritable – Heritability for IQ range 0. 6 to 0. 8 • General cognitive ability • Quantitative trait loci (QTLs) Chapter 5 Human Heredity by Michael Cummings © 2006 Brooks/Cole-Thomson Learning