own demise.

Some might argue that Desdemona also shows a possibility of deceitful behaviour when she elopes in the opening of the play with Othello.  It would have been highly improper and presumptuous for Desdemona to marry (from her station in society) without first obtaining her father's blessing and permission.  This, one could argue, makes her open to question later in the play.  If she made a move for love behind her father's back, mightn't she also do so behind Othello's back?  It does potentially leave her behaviour open to question and is worth considering.

However, it is the interesting part that the handkerchief plays in Othello, and even Desdemona's own part in the events surrounding it, that push Othello over the edge and lead to the play's tragic ending.

Desdemona is light and good, almost a Christ figure at the end.  She is the one character that Iago cannot corrupt.  Desdemona tells Emilia in Act 4 that Othello's unkindness may take her life but it will never "taint her love" for him.  These words prove to be true at the end of the play when Othello does indeed take Desdemona's life.  Desdemona dies still loving Othello. Her last words are "Commend me to my kind lord," even as she tries to absolve him from blame, claiming that she herself took her own life.

Othello has to choose between good (Desdemona) and evil (Iago).  A good and honorable man, Othello is convinced that Desdemona is evil and that Iago is good.  In Act 3, Othello severs his bond with Desdemona and in almost a parody of a wedding scene pledges his loyalty and love to Iago, swearing that he take revenge on Desdemona and Cassio.

In this way, Desdemona contributes to the tragedy.  Othello's wrong choice of Iago over Desdemona is his downfall.  All falling acting results from this decision.

But perhaps you were asking if Desdemona is in some way responsible for the tragedy.  Some would say her innocence and blindness to Othello's changing loyalties contribute to the tragedy.  But she is hardly to be faulted in her love for Othello and her inability to see him other than the honorable soldier who courted her and won her love.  You can see her innocence when Othello tells Desdemona that her hand is hot and moist--a double entendre in which he is suggesting that Desdemona is promiscuous.  Desdemona responds with "It was the hand that gave my heart away."  She does not understand his coarse language.  Another example of her innocence and naivete is when she asks Emilia if there are some women who do cheat on their husbands.  Emilia responds in the affirmative.  Desdemona replies that she would not cheat on Othello for the whole world.

I hope these examples help.

Desdemona's weaknesses are, ironically, related to her strengths. She is a strong, wilful young woman who defies her father in choosing to marry Othello. Having made her choice, she remains loyal to her husband even after he turns against her due to Iago's vile machinations. She continues to proclaim her love, come what may. Desdemona stands up for what she believes in, whether it's her love for Othello or her championing of Cassio's cause. Unfortunately, this creates problems for her, leading eventually to her downfall. In showing loyalty to both Othello and Cassio, Desdemona has inadvertently made it easier for Iago to destroy her. Perhaps Desdemona's greatest weakness is also one of her most admirable qualities—her ability to stand up to Iago:

O fie upon thee slanderer. (Act II Scene I).

Sadly, Desdemona's courage ultimately avails her nothing. She is too much of an individual, too loyal to her principles and the people she loves to survive in such a harsh, brutal environment.

Desdemona is Othello's loving wife, who was born to a Venetian senator. Although Othello is not of nobel birth, a Moor and probably dark-skinned, Desdemona loves Othello simply for who he is. This allows Iago to place suspicion in Othello's mind about how faithful she is. Her role is to serve as a catalyst for Othello's jealousy and eventual downfall, which is engineered by Iago. Desdemona seems clueless that she is being manipulated by Iago and cannot imagine that Othello would mistrust her because she has done nothing to deserve his mistrust. However, Othello,like many self-made men, is still insecure in his success and is therefore open to Iago's suggestions that Desdemona is unfaithful, Othello kills his wife in a fit of jealousy and then is so remorseful and dishonored that he kills himself.

Short answer: To the extent that Desdemona becomes submissive and allows herself to be victimized, as well as her lying about the loss of the treasured handkerchief that Othello gives her, she contributes to her tragic end.

It is so often one of the great ironies of marriages that what first attracts people to one another and leads to their engagement and wedding often becomes the same element that effects the undoing of those marriages. Desdemona's attraction to the great warrior who tells her exciting tales of battle excites her to a desire to be part of his life. He, in turn, may well be attracted by her fierce independence in her conviction to marry him against the social prejudices of her Venetian society, as well as her allegiance to him when she speaks to her father who demands her obedience:

I am hitherto your daughter. But here’s my husband.

And so much duty as my mother showed

To you, preferring you before her father,

So much I challenge that I may profess

Due to the Moor my lord. (1.3.186-190)

EMILIA.    Here's a change, indeed,
DESDEMONA.  'Tis meet I should be used so, very meet.
               How have I been behaved that he might stick.
               The small'st opinion on my least misuse. (4.2.111-114) 

Desdemona becomes an innocent victim of Iago's malicious manipulation. Since the devious and vengeful ancient knew much about her nature, he could easily target what he believed were weaknesses that he could exploit. He states at one point:

...For 'tis most easy
The inclining Desdemona to subdue
In any honest suit:

Iago knows that Desdemona would help anyone if she could. At this particular point, Cassio had been dismissed by Othello and Iago had advised the distraught ex-lieutenant to approach Desdemona and ask her to speak to her husband on his behalf. Iago told him that since Desdemona had so much influence on her husband, he would more than likely listen to her.

Iago had plotted to use Cassio's pleas to Desdemona to spur Othello's jealousy. He would tell him that his wife's constant request regarding Cassio was because she wished to satisfy her lust for the young Florentine. The good-natured Desdemona falls easily into Iago's trap. When Cassio approaches her with his request, she says:

Be thou assured, good Cassio, I will do
All my abilities in thy behalf.

She guarantees that her appeal on his behalf will be successful:

O, that's an honest fellow. Do not doubt, Cassio,
But I will have my lord and you again
As friendly as you were.

I know't; I thank you. You do love my lord:
You have known him long; and be you well assured
He shall in strangeness stand no further off
Than in a polite distance.

When Othello and Iago approach, Cassio slips away, prompting Iago to make the following remark:

Ha! I like not that.

When Othello wishes to know the reason for his retort, Iago acts as if he had not said anything inappropriate, making Othello even more suspicious. When Othello asks whether it is Cassio he is speaking about, he says:

Cassio, my lord! No, sure, I cannot think it,
That he would steal away so guilty-like,
Seeing you coming.

This makes the general even more suspicious and when Desdemona does approach him and asks about Cassio, he becomes quite irritated with her. She tells him:

How now, my lord!
I have been talking with a suitor here,
A man that languishes in your displeasure.

Desdemona's word choice actually adds fuel to the fire. Calling Cassio a suitor would later prove to have been an inappropriate term. She then requests that Othello give Cassio a hearing, but he says that he does not have the time. Unknowingly, since she thinks that she is doing Cassio a favor, Desdemona's repeated nagging about the matter irritates Othello even further and would eventually make it easy for Iago to convince him that the two are, indeed, lovers. She is unwittingly digging her own grave.

Desdemona's carelessness with the handkerchief Othello gave her also leads to her being implicated later. When she lets the handkerchief fall, she makes no attempt to recover it, giving Emilia the opportunity to take it and later give it to Iago. When Othello later asks for it, she can only say that she has lost it.

The handkerchief becomes ocular proof for Othello in proving her betrayal later, for Iago takes the handkerchief and places it in Cassio's rooms, where he finds it and later asks Bianca to remove the embroidery, an act witnessed by Othello. He immediately believes that Desdemona gave his most precious gift to her lover.

Throughout the period that Othello suspects her of an affair with Cassio, Desdemona does not challenge her husband enough to present evidence to support his accusations. She is almost apathetic about it. She only denies his accusation that she is a prostitute:

No, as I am a Christian:
If to preserve this vessel for my lord
From any other foul unlawful touch
Be not to be a strumpet, I am none.

When he smacks her in public, she does not confront him about his actions and is rather accepting, almost servile. She says that she would not stay to offend him and walks away.

Another aspect which one might consider is Desdemona's easy acquiescence to her husband's threat that he is going to kill her. She does not cry out for help nor make any attempt to escape. She almost willingly accepts that she has to die. She only asks the Lord to have mercy on her and again denies having an affair.

And have you mercy too! I never did
Offend you in my life; never loved Cassio
But with such general warranty of heaven
As I might love: I never gave him token.

Othello then strangles or suffocates her, and she later dies.

Desdemona has many positive qualities. She is a beautiful, charming young woman who proves she has a mind of her own when she marries the man of her choice and not any of the various suitors that her family propose for her. Indeed, she goes against all the conventions of her society in marrying a man not of her own race. She proves to be an utterly loyal wife to him, but this very loyalty proves her undoing in the end, as she never for a moment believes that he could ever turn against her, and so makes her an all-too easy target for his wrath. Or maybe it would be more accurate to say that she is simply too trusting, always ready to believe the best of everyone. Therefore she generally comes across as someone who is scarcely aware of the evils in the world. Perhaps her initial happiness with Othello helps to make her too complacent. She is pure and innocent, but too naive.