You create a hybrid transgene containing DNA from a human and a mouse. Which factor would most strongly affect when, where, and how much protein is expressed from that gene?

The gene's regulatory region

Explanation:

Gene regulatory region contains some gene sequences that control when, where, and how much protein will be expressed from that gene. These gene regulatory regions are found on DNA and RNA which binds with activator or repressor proteins or factors that regulate the transcription or translation genes in both prokaryotes and eukaryotes.

So the expression of genes in a hybrid transgene DNA will be dependent on the gene's regulatory region present in that transgene. The binding and dissociation of regulatory factors with and from the gene regulatory region will strongly affect when, where, and how much protein will be expressed from that gene.