*****Multifactorial Inheritance

Question 1

Identify and describe the characteristics of diseases and other traits that demonstrate multifactorial inheritance

Answer 1

When there is an increased risk to relatives, but there is no consistent pattern of inheritance within families.
Thus: assume multiple genes and environmental factors contribute to disease susceptibility, but these genes may or may not include the genes that cause the disease in patients showing Mendelian inheritance.
To add to the complexity, the same disease may be the outcome of different multifactorial pathways.
While inheritance of the disease may indeed follow such Mendelian patterns, it is often the case that the manifestation of the disease shows great variability among those with the same genetic risk factor(s)
Likely due to variants in multiple genes and non-genetic factors that may interact
No simple relationship between genetic variant and trait when looking at the population
Incomplete penetrance
Variable expressivity
Heterogeneity – allele and locus
Presence of phenocopies

Question 2

Give specific examples of diseases and other traits that demonstrate multifactorial inheritance

Answer 2

Some cancers
Diabetes
Alzheimer's
IBD
Schizophrenia
Cleft lip / palate
Hypertension
Rheumatoid arthritis
Asthma

Question 3

Describe the strategies used to determine the relative importance of genetic vs. non-genetic factors in contributing to the variation in a complex trait

Answer 3

Raised together: MZ > DZ = Genetic
Raised apart: If MZ still have similarities = Genetic
Look at adoption: If biosib1 = biosib2 (even though raised apart), it’s genetic. If adopted sibs are same, it’s environment.