Hox genes are sometimes called "master switches". They have acquired this nickname because a single Hox gene will turn on (or off) several related genes. That means that a single Hox gene cannot have a large effect on phenotype.

A. True

B. False

B. False

Explanation:

“Hox” genes are a highly conserved group of genes, all of whose products are transcription factors bearing a specific domain (called a ”homeodomain”). The transcriptional activity of a large amount of genes relevant to embryonic development is controlled by regulatory sites which are able to bind to this domain. Changes in the transcriptional activity of even a single Hox gene may thus have dramatic downstream effects on the phenotype, as this will result in several further genes having their transcription either enhanced or suppressed.

"a.) well–developed vascular system."