Transcript Chapter 1 A Perspective on Human Genetics

Concordance
When both twins express the
same trait
Chapter 5 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning
Chapter 5 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning
Chapter 5 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning
Survey of Multifactorial Traits
• Obesity
• Cardiovascular disease
• Skin Color
• Intelligence
Chapter 5 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning
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 Cummings ©2006 Brooks/Cole-Thomson Learning
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Experiments with parabiotic mice
Chapter 5 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning
ob - Leptin
db - Leptin receptor
Chapter 5 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning
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
1p31
– 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 ©2006 Brooks/Cole-Thomson Learning
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
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Heredity
Male
Hypertension
High LDL or low HDL
Smoking
Obesity
Lack of exercise
Stress
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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 ©2006 Brooks/Cole-Thomson Learning
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Skin color
• Controlled by more
than two genes
Fig. 5.18
Chapter 5 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning
Skin Color
Fig. 5.19
Chapter 5 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning
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
Correlation in IQ Measurements
Fig. 5.21
Chapter 5 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning