In the following table, average differences of height, weight, and fingerprint ridge count between monozygotic twins (reared together and apart), dizygotic twins, and nontwin siblings are compared: 

Based on the data in this table, which of these quantitative traits has the highest heritability values?

Verified step by step guidance

1. Step 1: Understand the concept of heritability in this context. Heritability measures the proportion of phenotypic variation in a trait that is due to genetic differences among individuals. Lower average differences between genetically identical individuals (like monozygotic twins) compared to less genetically related individuals (like dizygotic twins or siblings) suggest higher heritability.
2. Step 2: Compare the average differences for each trait between monozygotic (MZ) twins reared together and apart, dizygotic (DZ) twins reared together, and siblings reared together. Smaller differences in MZ twins relative to DZ twins and siblings indicate stronger genetic influence.
3. Step 3: For each trait (height, weight, ridge count), observe the pattern of differences: the smaller the difference in MZ twins compared to DZ twins and siblings, the higher the heritability. For example, height shows very small differences in MZ twins (1.7 and 1.8) compared to larger differences in DZ twins (4.4) and siblings (4.5).
4. Step 4: Note that weight shows a larger difference in MZ twins reared apart (4.5) compared to reared together (1.9), which suggests environmental factors also play a role. Ridge count differences are generally smaller but the difference between MZ and DZ twins is less pronounced.
5. Step 5: Conclude which trait has the highest heritability by identifying the trait with the greatest difference between MZ twins and DZ twins/siblings, indicating the strongest genetic influence.

Key Concepts

Heritability

Heritability measures the proportion of observed variation in a trait among individuals that can be attributed to genetic differences. It ranges from 0 to 1, where higher values indicate a stronger genetic influence. Heritability is often estimated by comparing trait similarities between relatives with different genetic relatedness.

Twin Studies

Twin studies compare monozygotic (MZ) twins, who share nearly 100% of their genes, with dizygotic (DZ) twins, who share about 50%. Differences in trait similarity between these groups help estimate genetic and environmental contributions. MZ twins reared apart provide insight into genetic effects independent of shared environment.

Quantitative Traits and Environmental Influence

Quantitative traits, like height, weight, and fingerprint ridge count, vary continuously and are influenced by multiple genes and environmental factors. Comparing trait differences among relatives reared together or apart helps distinguish genetic effects from environmental ones, clarifying the trait's heritability.