If you watch Degrassi, they have gay, lesbian, bisexual, and even transgnder persons on there that are main characters.
Marco is a gay guy. He comes onto the show in the second season (when it was known as Dehrassi: The Next Generation).
Paige finds out she is bisexual in season 5.
Alex (female) realizes she is a lesbian in season 5 and ends up dating Paige.
Fiona, who came on the show in season 8 or 9 (I think) is a lesbian.
Imogen, who came on the show in season 10 I think it was, is I think bisexual. (she had a crush on and dated Eli for a little bit, but then after they broke up, she started dating Fiona)
Adam, who came on the show in season 9 or 10, is a transgender. He was born a female named Gracie, but dresses and acts like a male.
All of the people listed above are/were main characters on the show. Marco, Paige, and Alex are now off the show aince the writers decided to focus more on Eli, Dave, Claire, and all of the other people who came onto the show from seasons 7 8 and 9.