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.
E) gene duplication.

Question

Quizplus · Accepted Answer

The genetic change that caused a Hox gene to be expressed differently is an example of a change in a developmental gene or its regulation, which altered the spatial organization of body parts. This is known as a cis-regulatory change and can lead to the evolution of novel features or structures in organisms.

Answer: D
 Heterochrony refers to changes in the timing of developmental events, such as the rate of growth or the onset of maturation. While this type of change can also contribute to the evolution of new features, it is not the most relevant concept for this particular example, in which a change in Hox gene expression altered the spatial organization of body parts.

Answer: A, B, E
 None of these choices accurately describes the genetic change that helped make the tetrapod limb possible. Environmental influences on development, paedomorphosis, and gene duplication can all be important factors in evolution, but they are not specifically relevant to this example.

A Genetic Change That Caused a Certain Hox Gene to Be