Dioxin is a chemical byproduct made during manufacturing. Animal testing has shown that it can have negative effects on organisms such as birth
defects, liver damage, and immune suppression. However, the effects vary
greatly between species. A mouse may be able to handle a higher dose than a
cat. Dioxin enters a cell and binds to a receptor protein, which then attaches
to the cell's genetic material. How does dioxin's mechanism contribute to its
variable effects on different organisms?
A. Organisms that do not require receptor proteins to initiate genetic
expression are not affected by dioxin.
B. Dioxin only binds to receptor proteins that affect particular genes
in particular species.
C. Dioxin may bind to receptor proteins that inhibit expression in
some genes and promote expression in others.
O D. Genes that are inhibited by receptor proteins are not affected by
dioxin since they are not expressed anyway.