Genetic Basis of Multifactorial disease Flashcards
Describe the contribution of genetic and environmental factors
Some diseases are almost exclusively genetic (eg, cystic fibrosis) some diseases are a combination of both genetic and environmental (eg, heart disease) and some are almost exclusively environmental (eg, trauma) but still has some genetic factors
What is quantitative inheritance?
Complex disorders and continuous traits which are influenced by multiple genes and multiple environmental factors
What are single gene disorders?
Deterministic
What are complex traits?
Even if you have all susceptibility alleles, disease still depends on environmental hazards.
What is the liability threshold model?
Where all the factors which influence the development of a multifactorial trait/disorder can be considered as a single entity
What is to the right of the threshold on a liability curve?
The incidence of disease in the general population
What is the familial incidence?
The proportion above the threshold on a liability curve
What is heritability of a trait/disease?
It is the proportion of the total variance that is genetic
What is the overall variance of a phenotype?
The sum of the environmental and genetic variance.
What is polymorphism?
Any variation in the human genome that does not cause a disease on its own but can predispose to a common disease.
What is synonymous polymorphism?
Changes in DNA sequence that doesn’t change the amino acid or subsequent protein
What is non-synonymous missense polymorphism?
Changes in the DNA sequence and amino acid and protein produced
What is non-synonymous nonsense polymorphism?
Changes to DNA sequence to code for a premature stop codon.
What are some of the limitations of family studies?
It does not take into account the risk caused by shared environment such as a familial predilection for hamburgues in siblings
How will the liability curve appear for affected relatives?
It will shift to the right as the familial incidence is higher than the general population