Polygenic inheritance Original Scenario-Based Download PDF

Questions

1. 1.

   In an isolated subterranean cavern, researchers study the luminous pulse duration of a newly discovered crystal beetle. Genetic analysis shows that pulse duration is a polygenic trait controlled by three independently assorting, unlinked gene pairs ($A$, $B$, and $C$), where each uppercase allele adds an equal increment of 10 seconds to a baseline duration of 20 seconds. When two moderately luminous beetles with the genotype $AaBbCc$ are crossed, which prediction accurately characterizes the pulse durations among their progeny?

   • A) Progeny will separate into distinct phenotypic categories following a strict 9:3:3:1 ratio because dominant alleles at the first locus mask the remaining loci.
   • B) Exactly half of the progeny will display the baseline phenotype of 20 seconds due to incomplete dominance across the three pairs of alleles.
   • C) Progeny will display a bell-shaped distribution of durations ranging from 20 to 80 seconds, with the intermediate duration of 50 seconds occurring most frequently.
   • D) All progeny will express an identical 50-second duration because polygenic mechanisms suppress phenotypic variation in filial generations.