How is heritability estimated in twin studies?
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By using concordance rates and correlation coefficients in MZ and DZ twins.
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How is heritability estimated in twin studies?
By using concordance rates and correlation coefficients in MZ and DZ twins.
What can affect the genetic identity of MZ twins?
Somatic mutations or differences in methylation patterns.
What are recurrence risks derived from?
Large family studies and vary between populations.
What is the recurrence risk for Autosomal Dominant diseases if fully penetrant?
50%.
What is a challenge in twin studies regarding MZ twins?
Environmental similarity can inflate estimates of genetic influence.
What defines multifactorial traits?
Traits influenced by both genetic and environmental factors, such as height and blood pressure.
What are quantitative traits?
Traits measurable on a continuous scale, often following a normal distribution, like blood pressure and height.
What are additive effects in the context of multifactorial inheritance?
The collective influence of many genes and environmental factors on a trait, resulting in a normal distribution.
What do correlation coefficients measure in twin studies?
They are used for quantitative traits, indicating genetic influence based on higher correlation in MZ twins.
What are polygenic traits?
Traits influenced by multiple genes, each contributing a small effect and following Mendelian inheritance.
What do separated MZ twin studies provide?
Insights by reducing shared environmental factors, though they are rare and have limitations.
What percentage of birth defects result from multifactorial inheritance?
Approximately 20-25%.
What is a common example of a multifactorial birth defect?
Cleft Lip and Palate.
What is Clubfoot (Talipes Equinovarus)?
A congenital deformity resulting in the foot being twisted out of shape or position.
What is Congenital Hip Dislocation?
A condition where the hip joint dislocates due to abnormal development.
What are Neural Tube Defects?
Defects that occur when the neural tube fails to close completely during early embryonic development.
What is the sibling recurrence risk related to population prevalence?
Approximately equal to the square root of the population prevalence.
What is sibling recurrence risk in multifactorial diseases?
The risk of disease in relatives influenced by the sex of the proband and their liability threshold.
What do concordance rates measure in twin studies?
Whether both twins in a pair share a trait.
What is the recurrence risk for Autosomal Recessive diseases if both parents are carriers?
25%.
How do recurrence risks for multifactorial diseases compare to single-gene disorders?
Generally much lower and depend on population data.
What increases the recurrence risk for multifactorial diseases?
Having more than one affected family member.
How does the severity of expression in the proband affect recurrence risk?
More severe expression increases the recurrence risk for relatives.
How do sex-dependent thresholds affect disease manifestation?
Different sexes may have different thresholds for disease manifestation, such as pyloric stenosis having a lower threshold in males.
How does recurrence risk for multifactorial diseases differ from single-gene diseases?
Recurrence risk for multifactorial diseases is more complex due to the involvement of multiple genes and environmental factors.
How do MZ twins' concordance rates compare to DZ twins for genetically determined traits?
MZ twins should be concordant more often than DZ twins.
What are Quantitative Trait Loci (QTLs)?
Loci that contribute to quantitative traits, identified through studies like genome-wide association studies (GWAS).
What is the threshold model in multifactorial inheritance?
A model where some diseases are either present or absent, influenced by multiple factors rather than following a normal distribution.
What is the liability distribution in the threshold model?
A curve representing varying levels of genetic and environmental risk for a disease in the population.
What does the threshold of liability indicate?
Disease manifests only when a certain threshold is crossed on the liability curve.
What are monozygotic (MZ) twins?
Identical twins originating from a single embryo that splits.
What are dizygotic (DZ) twins?
Fraternal twins resulting from two separate eggs fertilized by different sperm.
