Chop is a Rottweiler and Franklin will be able to use him in many missions when he is with him. During some missions you will be able to switch to Chop so that you can find certain packages and people.
In Franklin's House, Chop is shown to be attacking D; leading to the conclusion that he can help Franklin during fights. However, it is unknown if other dogs will do the same. Chop can also help the player to find hidden packages. There will be a throwable ball in the character's weapon menu, allowing you to be able to throw the ball for Chop to catch.
It was said in a interview with a Japanese magazine that Chop can be killed in gunfights. Chop can also be customized. Change the collar color to the player's liking or even give him a bandanna if they wish. Unfortunately, this is all unconfirmed and was taken from a source of unknown reliability.