Linked genes and recombination Original Scenario-Based Practice

Questions

1. 1.

   Dr. Vane crosses a true-breeding starlight beetle displaying shimmering wings and emerald bioluminescence with a true-breeding matte, sapphire-glowing strain to produce heterozygous F1 hybrids. When these F1 beetles are mated to homozygous matte, sapphire partners in a testcross, the resulting 1,000 offspring consist of 405 shimmering emerald, 395 matte sapphire, 105 shimmering sapphire, and 95 matte emerald individuals. Dr. Vane evaluates these phenotypic ratios to determine the physical relationship between the two trait-determining loci. Which conclusion correctly accounts for the genetic mechanism and map distance underlying these results?

   • A) The two gene loci assort independently on separate non-homologous chromosomes, deviating from an equal ratio solely due to environmental temperature shifts during larval development.
   • B) The genes exhibit complete linkage on the same chromosome with no homologous exchange, so the novel phenotypes arose exclusively via somatic mutations.
   • C) The genetic distance between the two loci is 40 map units because the recombination frequency must be calculated by summing each parental class independently.
   • D) The two loci reside on the same chromosome approximately 20 map units apart, and crossing over during prophase I generated the recombinant phenotypes.

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