Genetic disorders II Flashcards
What is a multigenic phenotype?
A phenotype which is controlled by multiple genes
What did RA Fischer say about mendelian units?
Several mendelian units contribute additively to the phenotype of a trait
What did Fischer say about dominance/recessiveness?
No alleles display dominance/recessiveness, though different alleles can have different sized effects on the phenotype
What is a consequence of Fischers model regarding siblings inheritance of diseases?
The proportion of siblings within families being affected by the same disease wwould be much lower than for mendelian models
What is the disease threshold?
Only when genotypes sum to reach a certain threshold can a disease manifest
What is the Carter effect?
Some complex diseases display sex dimorphisms
How has the effect of an individuals environment on the severity of a disease been studied?
Using twin studies
How has it been proven that some environmental factors are involved in the inheritance of diseases?
There is not a 100% concordance between monozygotic twins of inheriting the disease
What two things can phenotypic variance be affected by?
heritable genetic variance and environmental variance
What is broad sense heritability?
The proportion of phenotypic variance attributable to genetic causes
What is narrow sense heritability?
The proportion of phenotypic variance attributable to additive gene effects
What level of significance are somatic mutations thought to play in disease manifestation?
Not a significant one
Why is the effect of a somatic mutation greater if it occurs earlier?
It will affect more cells as it will be passed down via mitosis
Why is the brain susceptible to be more affected by somatic mutations?
Only a small amount of tissue needs to be affected to have a large phenotypic effect
