FTM 59 - Multifactorial Inheritance Flashcards
The majority of human genetic disorders are _____________.
Multifactorial
What are the 4 general types of genetic disorders?
Single Gene
Chromosomal Abnormalities
Mitochondrial
Multifactorial
Describe the inheritance pattern of multifactorial diseases.
They do not display a clear Mendelain pattern of inheritance but do show familial aggregation
What can be determined about multifactoral traits from the number of phenotypes present in a population?
The more phenotypes present, the more genes there are that control that phenotype
What is the disease liability/threshold model? What does it attemp to do?
The model asserts that multigenic diseases have a number of factors both genetic and environmental that contribute to a person’s liability of expressing that disease phenotype. It also asserts that multigenic diseases have a theoretical threshold and that individuals with a liability past that threshold are likely to express that disease phenotype. This model attempts to describe a population’s genetic and environmental susceptibility to a disease through the use of bell curves.
Discuss familial relative risk.
What is a relative risk ratio and how is it calculated?
A relative risk ratio is a comparison of the aggregation of a disease in a family vs the prevalence of that disease in the general population.
Discuss cleft lip/palate in relation to the liability threshold model.
The risk of recurrence for this disease is higher in relatives if the disease is more severe in an individual (ie - a bilateral cleft lip and palate instead of just a unilateral cleft lip).
Discuss pyloric stenosis in relation to the liability/threshold model.
Pyloric stenosis is more prevalent in males so if it is present in a female then the recurrence risk of her family members is higher than if it would have been in her brother.
Also boys in the family are more at risk then the girls
What types of studies are done to help separate genetic from the environmental causes of a disease?
How can twins be used to differentiate genetic from environmental causes for a disease?
MZ twins are geneticaly identical. If a disease is concordant between MZ twins then that disease is ~100% genetically determined. If is disconcordant between MZ twins then that disease is <100% genetically determined. The greater the discordance the greater the environmental input.
Discuss what an association study is and how it is used to separate genetic from environmental causes for a disease.
An association study tests the co-occurrence of a specific allele at a marker locus and a trait in a population by comparing the frequency of that allele in a health population versus a diseased population. Association studies do not concern familial inheritance patterns at all.
Which neural tube defects show multifactorial inheritance?
Anencephaly and Spina bifida
What is the evidence that spina bifida is genetically controlled? Environmentally controlled?
