Quantitative Genetics 2: Twin Studies

A represents additive genetic effects, C represents shared environmental effects, and E represents non-shared environmental effects.

An ADE model is favored when the condition rMZ > 2rDZ is met.

For rMZ = 0.75 and rDZ = 0.10, A = 1.30, C = -0.55, and E = 0.25.

<p>The letter D denotes dominant genetic effects in the ADE model.</p> Signup and view all the answers

<p>When rMZ is greater than rDZ, it suggests that genetic factors contribute more to the variance than environmental factors, indicating a need for an ADE model.</p> Signup and view all the answers

<p>MZ twins are genetically identical while DZ twins share approximately 50% of their genetic variance.</p> Signup and view all the answers

<p>Twin studies compare MZ and DZ twin correlations to assess the genetic contribution to trait variance in a population.</p> Signup and view all the answers

<p>Heritability is the proportion of trait variance in a population that can be attributed to genetic variation.</p> Signup and view all the answers

<p>'A' represents additive genetic effects in Falconer's formula.</p> Signup and view all the answers

<p>Africa has the highest twinning rates, ranging from 18 to 30 pairs per 1,000 births.</p> Signup and view all the answers

<p>The components of variance are additive genetic effects (A), common/shared environment effects (C), and non-shared environmental effects (E).</p> Signup and view all the answers

<p>In Falconer's formula, the MZ correlation (rMZ) equals A + C, while the DZ correlation (rDZ) equals 0.5A + C.</p> Signup and view all the answers

<p>It is important to understand these rates to investigate genetic and environmental factors that contribute to twinning.</p> Signup and view all the answers

<p>rMZ represents the correlation between monozygotic twins, while rDZ represents the correlation between dizygotic twins.</p> Signup and view all the answers

<p>A is calculated using the formula $A = 2(rMZ - rDZ)$.</p> Signup and view all the answers

<p>Vp stands for phenotypic variance, which is the total variance in a trait observed in a population.</p> Signup and view all the answers

<p>E is computed using the formula $E = 1 - rMZ$.</p> Signup and view all the answers

<p>A = 0.20, C = 0.60, E = 0.20.</p> Signup and view all the answers

<p>A high rMZ correlation relative to rDZ suggests a strong genetic influence on the trait being studied.</p> Signup and view all the answers

<p>If rMZ and rDZ are the same, it indicates that the additive genetic effect (A) is zero and the common environmental effect (C) is equal to that correlation.</p> Signup and view all the answers

<p>A high value of E indicates significant non-shared environmental effects, suggesting that individual differences are largely due to unique experiences.</p> Signup and view all the answers

The correlation between monozygotic (MZ) twins on a trait.

The correlation between dizygotic (DZ) twins on a trait.

A statistical model used in twin studies to estimate the influence of additive genetic effects (A), shared environment (C), and unique environment (E) on a trait.

A statistical model used in twin studies to estimate the influence of additive genetic effects (A), dominant genetic effects (D), and unique environment (E) on a trait.

The condition when the correlation between monozygotic twins (rMZ) is greater than twice the correlation between dizygotic twins (rDZ), suggesting that dominant genetic effects might play a significant role in the trait.

The extent to which genetic factors contribute to a trait, calculated as twice the difference between MZ and DZ twin correlations

The extent to which factors shared by twins in the same environment contribute to a trait

The extent to which unique experiences and influences not shared by twins contribute to a trait

To calculate the contribution of each factor (A, C, and E) to a trait's variation, we utilize the MZ and DZ twin correlations. These correlations are influenced by both genetic and environmental factors.

The specific formula for calculating A using the MZ and DZ twin correlations. It reflects the difference in genetic similarity between MZ and DZ twins.

The specific formula for calculating C using the MZ twin correlation and the calculated additive genetic effect (A). It emphasizes the shared environment's influence on the trait.

The rate of twin births varies across the globe, with Africa having the highest rate and Asia having the lowest.

Identical twins, also known as monozygotic twins, arise from a single fertilized egg that splits, resulting in two individuals with identical genetic makeup.

Fraternal twins, also known as dizygotic twins, develop from two separate fertilized eggs, making them genetically siblings.

Twin studies are a valuable tool in genetics, comparing MZ and DZ twins to estimate heritability, which is the proportion of trait variance in a population attributed to genetic variation.

Twin studies analyze the correlations between MZ twin pairs and DZ twin pairs to understand the relative influence of genetics and environment on traits.

Falconer's formula is a mathematical model that uses twin data to estimate the influence of genetics (A), shared environment (C), and non-shared environment (E) on a trait.

The common environment effects (C) represent the shared environmental factors that influence twins similarly.