Answer the following in regard to multifactorial traits in human twins. If the trait is produced with little contribution from genetic variation, what would you expect to see if you compared the concordance rates of MZ twins versus DZ twins? Explain your reasoning.

Key Concepts

Concordance Rates

Concordance rates refer to the likelihood that both twins in a pair exhibit the same trait. In twin studies, these rates are compared between monozygotic (MZ) twins, who share nearly identical genetic material, and dizygotic (DZ) twins, who share about 50% of their genes. Higher concordance rates in MZ twins suggest a stronger genetic influence on the trait, while similar rates in both types of twins indicate a greater role for environmental factors.

Multifactorial Traits

Multifactorial traits are characteristics influenced by multiple genetic and environmental factors. Unlike single-gene traits, these traits do not follow simple Mendelian inheritance patterns. Examples include height, intelligence, and susceptibility to diseases. Understanding that these traits arise from the interplay of various influences is crucial for interpreting twin studies and their findings.

Genetic Variation

Genetic variation refers to the differences in DNA sequences among individuals, which can affect traits and predispositions to certain conditions. In the context of the question, if a trait shows little contribution from genetic variation, it implies that environmental factors play a more significant role. This would likely result in similar concordance rates for MZ and DZ twins, as the trait's expression is less dependent on genetic similarity.