Polygenic inheritance Original Scenario-Based Practice

Questions

1. 1.

   A marine geneticist explores a newly discovered abyssal lanternfish whose biofluorescent intensity ranges continuously from faint amber to dazzling crystalline blue. Breeding trials reveal that this trait is governed by four independently assorting gene loci, where each dominant allele exerts an equal, cumulative additive effect toward maximum blue brightness. When two moderately luminous fish, each heterozygous across all four gene loci, are mated, their thousands of offspring exhibit a smooth bell-shaped distribution of luminance intensities. Which statement best explains the genetic basis of the extreme phenotypes observed among these offspring?

   • A) The extreme phenotypes result from incomplete dominance at a single master locus that is intermittently modified by maternal cytoplasmic factors.
   • B) Faint amber offspring possess multiple epistatic suppressor alleles that systematically mask the expression of otherwise fully dominant blue alleles.
   • C) Environmental temperatures in the abyssal trench induce non-genetic modifications that determine whether light-emitting proteins fold properly.
   • D) The rarest phenotypes correspond to individuals inheriting either all non-contributing alleles or all additive alleles across the multiple loci.

Answers and step-by-step solutions appear after you finish the test.