What is the significance of jealousy in Othello?
In addition to the answers above, jealousy is tied to sexism, misogyny and the male and female reputations in the play Othello. The double standards of this patriarchal honor culture are such: males had the right to be jealous of women, but women had no right to be jealous of men. More, men were jealous of each other's rank, status and reputation.
I believe Othello is more jealous of Cassio than he is of Desdemona. Cassio is the ideal male, and he represents everything that Othello is not. He is young, white, Christian, well-spoken, and handsome.
Not only are males jealous of other males, but females are jealous of each other. Emilia and Bianca are jealous of Desdemona. Why do you think Emilia steals the handkerchief from Desdemona? Why do you think Bianca gives it back to Cassio? They hate what it represents: Desdemona's status as the highest ranking woman.
It is jealously that motivates Iago into his plan of setting everyone up for emotional pain and bringing about destruction to all who are happier than him. This becomes a plan borne out of jealously. It makes sense that Iago understands how jealously can motivate Othello, who is filled with doubt and insecurity regarding his relationship with Desdemona and his position of leadership. Jealously or desire for what someone else has motivates Iago and drives Othello to believe him. I am not sure the plan finds any success and gains traction without the presence of jealously in both of Iago's and Othello's hearts.