Domestic Rats Can Have Black,silver,or Light-Gray Patches on Their Necks

Essay

Domestic rats can have black,silver,or light-gray patches on their necks.A pure-breeding silver female was crossed to a pure-breeding black male,and the F₁ was comprised of black females and light-gray males.When F₁ brothers and sisters were mated,the resulting F₂ consisted of about ¼ black females,¼ black males,¼ silver females,and ¼ light-gray males.
Propose a model for the mode of inheritance of patch color in domestic rats.