Nicholas Holmes Scientific Portfolio

This observational study investigated self-reported eye color across three generations of a primary family unit, supplemented by data from unrelated individuals. The initial assessment revealed variation in eye color, even within the core family, suggesting a complex inheritance pattern rather than a simple Mendelian model. The first generation (n=4) exhibited a spectrum of blue, green, and brown eyes. The second generation, comprising five subjects, predominantly displayed blue and green eyes, with only one individual reporting brown eyes. Interestingly, the third generation (n=5) showed a different distribution, with individuals having either blue (n=3) or brown (n=2) eyes, and no reported green eyes in this cohort.

These findings align with the established understanding that human eye color is a polygenic trait, influenced by the interplay of multiple genes rather than a single gene locus (Sturm & Duffy, 2012). The primary genes involved regulate melanin production and distribution in the iris, leading to the observed phenotypic diversity (Sturm & Duffy, 2012). The variation seen within the family, where individuals across generations exhibit different eye colors despite familial relationships, is a hallmark of polygenic inheritance. Each parent contributes a unique set of alleles from these multiple genes, and the specific combination inherited by an offspring determines their eye color. For instance, parents with blue or green eyes can carry alleles that, when combined in their children, may result in brown eyes, or vice versa, depending on the complex interactions of these numerous genetic factors (White & Rabago-Smith, 2011). The shift in observed eye colors between the second and third generations in this study likely reflects the specific allelic combinations passed down, demonstrating how different phenotypic ratios can emerge due to the segregation and independent assortment of multiple contributing genes.