Multifactorial Inheritance

Question 1

What are the characteristics of diseases and other traits that demonstrate multifactorial inheritance?

Answer 1

• Variable disease progression (depending on other factors)
• Different alleles in same gene with varying levels of severity
• Increased risk to relatives without consistent pattern of (Mendelian mode of) inheritance within families
• No simple relationship between genetic variant and trait when looking at the population

Question 2

What is a specific example of diseases and other traits that demonstrate multifactorial inheritance?

Answer 2

• Some cancers
• Schizophrenia
• Diabetes
• Cleft lip/palate
• Hypertension
• Alzheimer disease
• Rheumatoid arthritis
• Inflammatory bowel disease
• Asthma

Question 3

What are the strategies used to determine the relative importance of genetic v. non-genetic factors in contributing to the variation of a complex trait?

Answer 3

• Twin studies
• Adoption studies
• Immigration studies

Question 4

What are some reasons that it is difficult to quantify the role of genetic factors in contributing to risk of disease at both population and individual levels?

Answer 4

• Have to distinguish b/w clustering in families due to genetics and those due to shared environmental factors
• Incomplete penetrance, variable expressivity, heterogeneity, and presence of phenocopies
• The role of non-genetic factors in contributing to variation in complex traits will vary from trait to trait and from individual to individual