p.3
Concordance Rates and Heritability Estimation
How is heritability estimated in twin studies?
By using concordance rates and correlation coefficients in MZ and DZ twins.
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Twin Studies in Genetics
What can affect the genetic identity of MZ twins?
Somatic mutations or differences in methylation patterns.
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Recurrence Risks for Multifactorial Diseases
What are recurrence risks derived from?
Large family studies and vary between populations.
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Twin Studies in Genetics
What is a challenge in twin studies regarding MZ twins?
Environmental similarity can inflate estimates of genetic influence.
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Principles of Multifactorial Inheritance
What defines multifactorial traits?
Traits influenced by both genetic and environmental factors, such as height and blood pressure.
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Principles of Multifactorial Inheritance
What are quantitative traits?
Traits measurable on a continuous scale, often following a normal distribution, like blood pressure and height.
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Principles of Multifactorial Inheritance
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.
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Concordance Rates and Heritability Estimation
What do correlation coefficients measure in twin studies?
They are used for quantitative traits, indicating genetic influence based on higher correlation in MZ twins.
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Principles of Multifactorial Inheritance
What are polygenic traits?
Traits influenced by multiple genes, each contributing a small effect and following Mendelian inheritance.
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Twin Studies in Genetics
What do separated MZ twin studies provide?
Insights by reducing shared environmental factors, though they are rare and have limitations.
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Examples of Multifactorial Birth Defects
What is Clubfoot (Talipes Equinovarus)?
A congenital deformity resulting in the foot being twisted out of shape or position.
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Examples of Multifactorial Birth Defects
What is Congenital Hip Dislocation?
A condition where the hip joint dislocates due to abnormal development.
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Examples of Multifactorial Birth Defects
What are Neural Tube Defects?
Defects that occur when the neural tube fails to close completely during early embryonic development.
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Recurrence Risks for Multifactorial Diseases
What is the sibling recurrence risk related to population prevalence?
Approximately equal to the square root of the population prevalence.
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Principles of Multifactorial Inheritance
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.
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Twin Studies in Genetics
What do concordance rates measure in twin studies?
Whether both twins in a pair share a trait.
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Recurrence Risks for Multifactorial Diseases
How do recurrence risks for multifactorial diseases compare to single-gene disorders?
Generally much lower and depend on population data.
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Recurrence Risks for Multifactorial Diseases
What increases the recurrence risk for multifactorial diseases?
Having more than one affected family member.
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Recurrence Risks for Multifactorial Diseases
How does the severity of expression in the proband affect recurrence risk?
More severe expression increases the recurrence risk for relatives.
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Principles of Multifactorial Inheritance
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.
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Recurrence Risks for Multifactorial Diseases
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.
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Twin Studies in Genetics
How do MZ twins' concordance rates compare to DZ twins for genetically determined traits?
MZ twins should be concordant more often than DZ twins.
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Principles of Multifactorial Inheritance
What are Quantitative Trait Loci (QTLs)?
Loci that contribute to quantitative traits, identified through studies like genome-wide association studies (GWAS).
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Principles of Multifactorial Inheritance
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.
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Principles of Multifactorial Inheritance
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.
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Principles of Multifactorial Inheritance
What does the threshold of liability indicate?
Disease manifests only when a certain threshold is crossed on the liability curve.
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Twin Studies in Genetics
What are monozygotic (MZ) twins?
Identical twins originating from a single embryo that splits.
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Twin Studies in Genetics
What are dizygotic (DZ) twins?
Fraternal twins resulting from two separate eggs fertilized by different sperm.
