How can I stop mosquitoes from entering my room?

I live with my father and stepmother who insist on leaving the back door open all the time and letting all kinds of flying insects into the house. The most problematic are mosquitoes as they bite me all the time. They seem to be oblivious to the fact that they exist as they say they do not bite them but I am covered in bites all the time. I keep the door to my room shut to keep most of them out but it still does not completely work, is there any way I can stop these bugs from getting in my room?