Final answer:
Homeobox genes, containing homeodomains, serve as transcription factors that regulate gene expression during early embryo development by binding to DNA and controlling the activity of other genes.
Step-by-step explanation:
Homeobox Genes and Early Embryo Development
The regulatory genes responsible for activation during early embryo development are homeobox genes. These genes are critical for ensuring that the correct genes are expressed in particular cells at the right time for normal development of organs and organ systems. Homeobox genes encode for homeodomains, which are sequences of 60 amino acids that enable proteins to bind to DNA and function as transcription factors. This binding influences the activities of other genes, effectively turning them on or off during the embryonic stage. In humans, approximately 235 homeobox genes have been identified, which play a vital role in dictating the developmental processes of an organism.
In summary, homeobox genes contain instructions for making chains of amino acids that create homeodomains, and the proteins containing these homeodomains act as transcription factors to control the expression of other important developmental genes.