See the explanation below.
Work Step by Step
Take notice that hox genes are valueable for the development of a basic body plan in several organisms. If any mutations in such an important gene loci occurred, it would result in severe abnormalities. This is manifested in their evolutionary conserved sequences. Mutations such as insertion of transportable elements would cause the reduction or loss in the expression of these genes. Therefore, such mutations are eliminated by cleansing the selection during the course of evolution.