Homeotic genes contain a homeobox sequence that is highly conserved among very diverse species. The homeobox is the code for the domain of a protein that binds to DNA in a regulatory developmental process. Which of the following statements is therefore correct regarding homeotic genes?
A) Homeotic genes are selectively expressed as an organism develops.
B) Homeoboxes cannot be expressed in nonhomeotic genes.
C) Homeotic genes in apes and humans are very different.
D) All organisms must have homeotic genes.

Question

Quizplus · Accepted Answer

Homeotic genes are selectively expressed during an organism's development, as they play a critical role in determining the identity of body segments and structures. The highly conserved homeobox sequence is necessary for the protein to bind to DNA and carry out regulatory functions. Therefore, the correct answer is A. B is incorrect because homeoboxes can be found in other genes, but they are not considered homeotic genes unless they are involved in developmental regulation. C is incorrect because despite some variation, the homeobox sequence is highly conserved in apes and humans, and homeotic genes have been identified and studied extensively in both species. D is incorrect because there are some organisms without homeotic genes, but they are relatively rare and have highly simplified body plans (such as sponge).

Homeotic Genes Contain a Homeobox Sequence That Is Highly Conserved