Polygenic inheritance Transitional Reasoning Download PDF

Questions

1. 1.

   A plant geneticist crosses a true-breeding short plant line with a true-breeding tall plant line of the same species, producing uniform intermediate-height offspring in the F1 generation. When individuals from the F1 generation are crossed with one another, the resulting F2 population exhibits a continuous range of heights resembling a normal bell-shaped distribution curve, rather than discrete height classes. Which of the following conclusions is best supported by these experimental observations?

   • A) Plant height is governed by multiple gene loci whose contributing alleles exert cumulative, additive effects on the phenotype.
   • B) Plant height is determined by a single pleiotropic gene that regulates multiple independent developmental pathways.
   • C) Plant height results from complete dominance at a single locus where environmental factors completely override genetic controls.
   • D) Plant height is controlled by two co-dominant alleles at a single locus that segregate into discrete phenotypic categories.