G5- Multifactoral disorders Flashcards
Name 4 types of genetic disease.
- chromosomal
- single gene
- multifactorial
- somatic mutation
Discuss heritability studies.
Features: more common in relatives
Not explainable by simple mendelian segregation
How is heritability assessed?
monozygotic/dyzygotic twins
parent/offspring correlation coefficients , correlation coefficients within sibling pairs
what is multifactorial inheritance?
- Continuous e.g. Height
- Features: normal distribution in the population
- Explainable by interaction of many genes
- Examples: stature, intelligence, cholosterol
- Discontinuous e.g. Orofacial clefting
what causes multifactorial disorders?
- interactions of variations in multiple genes and environmental factors
- The genes involved may make a person susceptible to the disorder, and the environmental factors may trigger the occurrence
which individuals will exhibit the phenotype?
Only individuals with enough genetic liability (multiple genes) who are in the presence of certain environmental factors
what do multifactorial disorders include?
heart disease, diabetes, asthma, and many birth defects, such as cleft lip +/- cleft palate
Describe the determination of recurrence risk.
- Usually derived directly from studies of affected families
- Risk in close relatives usually less than those observed with single gene disorders
- Risk sharply lower for second degree relatives
- Greater risk with greater number of family members affected
- Risk increases with severity
- Gender effect in disorders with gender bias
In the MFT model, what effect does the 3rd degree relatives have?
has barely any effect
Is there any effect on cleft lip from socio-economic status?
There is an association between increased deprivation and cleft lip
what environmental factors increased CL/P?
- Smoking
- Nutrition
- Teratogens (e.g. phenytoin)
- Geography
- Social class
- Alcohol
what does smoking amount women increase risk of CLP by?
30%
what role does folic acid have?
has an essential role in cell replication, it might be expected that insufficiency during early embryonic development could contribute to the aetiology of certain birth defects, including orofacial clefts
what is complexity in determination of environmental factors due to?
- Confounding evidence in the literature
- Maternal memory recall bias
- Threshold effects rather than presence/absence
- Relative effect of illness or disease/medication
- Differences in maternal metabolism
- Gene/environment interaction
what is gene/environment interaction?
‘A different effect of an environmental exposure on disease risk in persons with different genotypes’
what is epigenetics?
- Changes in phenotype or gene expression caused by mechanisms other than changes in the underlying DNA sequence (environment)
- Non-genetic factors cause the organism’s genes to behave (or “express themselves”) differently
what is an example of epigenetic?
cellular differentiation
Discuss dietary supplementation.
- Total population intervention with specific nutrients
- Targeted intervention preceded by screening
what is the translation to public health?
- Genetic counselling -> risk assessment
- Primary prevention -> to reduce occurrence and recurrence
what are the genetics of common dental disorders?
- Specifically genetic
- Genetic predisposition
- Tangible environmental influence
- Environment determines prevalence and severity
- Specifically environmental
Name an example of specifically genetic (1).
ectodermal dysplasia
Name an example of genetic predisposition (2).
cleft lip and palate
Name an example of evironment has an influence only in certain genotypes (3).
periodontal disease :
-Predisposition to periodontitis determined by smoking, bacterial deposits and host genetic factors
- Periodontal disease may
persist or progress even in the absence of environmental risk factors (good oral health)
Name an example of environment determines prevalence/severity (4)
long face “syndrome”
Name an example of environment only (5).
trauma
