Codominance Original Scenario-Based Download PDF

Questions

1. 1.

   On an expedition to a subterranean crystalline cavern, xenobiologists discover a species of luminous lizard with two pure-breeding strains: one displaying solid silver luminescence ($C^S C^S$) and another displaying solid golden luminescence ($C^G C^G$). Crossing these strains yields $F_1$ offspring that all exhibit discrete, alternating patches of fully radiant silver and gold light rather than an intermediate blended glow. If two of these patterned $F_1$ lizards are mated, which phenotypic ratio will appear in their $F_2$ progeny, and which genetic mechanism accounts for this outcome?

   • A) 3 solid silver : 1 solid gold, because the silver allele exerts complete dominance over the gold allele in all heterozygous combinations.
   • B) 1 solid silver : 2 soft bronze : 1 solid gold, because incomplete dominance causes the two pigment products to mix uniformly in heterozygotes.
   • C) 1 solid silver : 2 mottled silver-and-gold : 1 solid gold, because codominance allows both alleles to be fully and simultaneously expressed in heterozygotes.
   • D) 9 mottled silver-and-gold : 3 solid silver : 3 solid gold : 1 non-luminescent, because the two coloration traits are governed by two independently assorting gene loci.