Swallowtail butterfly tiger swallowtail), Y-linkage determines whether the females are either wild-type (yellow and black) or melanic (dark melanin replaces the yellow background). This genetic difference stems from the fact that melanism is controlled by a single gene, which controls the level of dopamine in the organism. The enzyme BAS, which assists dopamine in producing the yellow pigmentation, normally found on the wings' background, is suppressed. Without the pigmentation, the butterfly appears mostly black (the melanic form) and is a Batesian mimic of "Battus philenor", the pipevine swallowtail. There are also "Papilio glaucus" that are not wholly black; several possess an intermediate
Comma "coordinate adjectives" (i.e., adjectives that directly and equally modify the following noun). Adjectives are considered coordinate if the meaning would be the same if their order were reversed or if "and" were placed between them. For example: Some writers precede quoted material that is the grammatical object of an active verb of speaking or writing with a comma, as in "Mr. Kershner says, "You should know how to use a comma."" Quotations that follow and support an assertion are often preceded by a colon rather than a comma. Other writers do not put a comma before quotations unless one would