• Genetic Basis of Heterosis (Hybrid Vigor):
• According to Falconer & Mackay's quantitative genetics framework:
• When two inbred parental lines differing in gene frequencies ($p_1$ and $p_2$, where $y = p_1 - p_2$) are crossed:
• The amount of heterosis observed in the $F_1$ generation (the deviation of $F_1$ from the mid-parent value) summed across all loci is:

where:

• $d$ = dominance deviation at the locus
• $y = p_1 - p_2$ = difference in allele frequency between the two parental populations
• Heterosis strictly depends on the presence of dominance ($d$) and genetic divergence ($y^2$) between parental lines.
• nalysis:
• (dy^2): Correct formula ($dy^2$, OCR recorded as dy).

Correct option: (2) dy