A genetic change that caused a certain Hox gene to be expressed along the tip of a vertebrate limb bud instead of farther back helped make possible the evolution of the tetrapod limb. This type of change is illustrative of a. the influence of environment on development. b. paedomorphosis. c. a change in a developmental gene or in its regulation that altered the spatial organization of body parts. d. heterochrony.

Verified step by step guidance

1. Identify the key concept: The question describes a genetic change affecting the expression of a Hox gene, which influences the development of limb structures in vertebrates.
2. Understand the role of Hox genes: Hox genes are crucial in determining the body plan and the positioning of various structures during embryonic development. They control the anterior-posterior axis formation and help differentiate the types of structures that will form at specific locations.
3. Analyze the options: Option (c) mentions a change in a developmental gene or its regulation that altered the spatial organization of body parts, which directly relates to the role of Hox genes in determining where limbs and other structures develop.
4. Eliminate unrelated options: Options (a), (b), and (d) do not directly address changes in gene expression affecting spatial organization. Option (a) involves environmental influence, option (b) involves retaining juvenile features in adults, and option (d) involves timing changes in developmental processes.
5. Conclude with the correct answer: Based on the role of Hox genes in spatial organization during development, the correct answer is (c) a change in a developmental gene or in its regulation that altered the spatial organization of body parts.