• Breeding Value ($A$) in Quantitative Genetics:
• The breeding value of an individual represents the value of its genes transmitted to its offspring.
• Formally defined by Falconer & Mackay as the sum of the average effects of the alleles an individual carries across all loci influencing the quantitative trait:

• In terms of progeny testing, an individual's breeding value equals twice the expected mean deviation of its progeny from the population mean when mated randomly to a representative sample of the population.
• nalysis:
• (Sum of the average effect of alleles): Correct fundamental definition of breeding value.
• & 3: Progeny deviation is half the breeding value, not equal to or twice.

Correct option: (1) Sum of the average effect of alleles