Multifactorial Inheritance Flashcards
familial tendencies in MI
- they do exist but less common
- there is also no set pattern of inheritence
define proband
the first person in the family to be affected by the disease
the role of the environment in multifactorial disorders
it modifies gene expression - Epigenetics
gene effects can be
Protective
Additive
Complex
Synergestic (summative)
environment effects can be
Protective
Accelerate
Trigger
Exacerbate
2 distributions in multifactorial
- continuous - quantitative
- discontinuous - qualitative
continuous distribution - 5
- each gene ha an effect on phenotype
- genes do not have an equal effect
- bell shaped curve around the mean
- cumulative effect is normal distribution
- environmental factors can also have an effect
discontinuous distribution - 4 *
- every factor is a liability
- have a threshold to tolerance
- phenotype is abnormally expressed
- family members are moe liability factors
what is meant by the threshold model of discontinuous?
it means that an individual accumulates genetic and environmental risk factors. If the risks pass the threshold then they get affected
concordance vs discordance
twins have the same disease and traits (similar environment and genes), while in discordance one has it and one doesnt
dizygotic twins
share 50% genetic material, but they share the same lived environment
which set of twins provides more evidence for the genetic component
MZ
if MZ are reared apart
high degree of concordance would suggest significant genetic component
what is acertainment bias
when more notice is given to a condition if more than one twin is affected
common congenital disorders in MD - 4
- cleft lip and palate
- clubfoot
- congenital heart defects
- neural tube defects
Diseases of childhood or adulthood - 4
- HTN
- diabetes
- asthma
- psychiatric disease
hemophilia A penetrance
complete
Breast and Ovarian cancer penetrance
incomplete
identifying genes implicated in multifactorial diseases - TASCG
Twin studies
Adoption studies
Sib pair stdis
Case control
GWAS
GWAS
looks at non patient and patient DNA to find SNPs that can be linked to certain conditions
important points in MI
familial tendencies exist but less than single gene disoders
what is recurrence risk dependant on
on degree of relation to proband
when does neuralation begin
20-28 days post fertilization
which gender is most affected by neural tube defects
FEMALES
