Multifactorial Inheritance

Question 1

Types of non-Mendelian inheritance

Answer 1

• Polygenic
• Multifactorial (or common complex)
• Maternal mitochondrial

Question 2

How are genetic and environmental influences for multifactorial inheritance identified?

Answer 2

Observational studies of the incidence of diseases in different groups of people

Question 3

How is evidence gathered for observational studies?

Answer 3

• Familial clustering
• Twin studies
• Adoption studies
• Population and migration studies

Question 4

What is empiric risk?

Answer 4

Chance that a disease will occur in a family, based on experience with the diagnosis, past history and medical records rather than theory

Question 5

What is the threshold model of multifactorial inheritance?

Answer 5

• Bell-shaped curve with liability on x-axis and number of affected people on y-axis
• Liability caused by combination of genetic and environmental factors
• Threshold level is the point on the x-axis where the people above it have the disease

Question 6

How are the genetic components of common complex disorders identified?

Answer 6

Genome-wide association studies (GWAS)

Question 7

How does a genome-wide association study work?

Answer 7

• Take thousands of people knowing who does and doesn’t have the disease
• Test up to 500,000 SNPs in each person by microarray analysis
• Identify genetic alterations associated with disease

Question 8

By how much are risks usually increased by specific SNP genotypes?

Answer 8

1.1x - 1.5x