“Bad Jews” is a full-blooded modern comedy. Long Wharf Theatre’s new production of the 2012 play by Joshua Harmon runs through March 22 and turns a sharp script into a comic tour de force.

For 80 uninterrupted minutes, “Bad Jews” gives the domestic melodrama a humane and uproariously funny update: Four characters sprawl, walk, lounge and lunge across three futons in a studio apartment. The simple set plays host to an intra-family showdown over prized heirlooms and religious identity.

The show’s outrageous turmoil is absent from the opening sequence, which introduces Jonah (Max Michael Miller) and Daphna (Keilly McQuail). They’re Jews, we learn. They’re cousins. They’re college students. They’re in his apartment in Manhattan. They’ve just come back from their grandfather Poppy’s funeral. For this stretch, “Bad Jews” is basically a one-woman show, as Jonah, catatonic, plays video games and says nothing, throwing into relief his cousin, a Vassar student who regales him with her newfound Jewish fanaticism. Daphna plans to become a rabbi, find a vegan mentor, make aliyah to Israel, join the army, marry her Israeli boyfriend, and on, and on, and on.

The force of McQuail’s performance easily sustains the play: She’s an archetypal Jewish-American princess, at once vain, overbearing and sympathetic. She kvells, she kvetches, she pontificates, all with exaggerated Orthodox-Jewish enunciation. Her long, icy glares at Jonah elicit peals of laughter from the audience. She extracts humor from throwaway lines like, “I’m not even saying, I’m just saying!”

Daphna’s presence is a dramatic conflict in itself, capable of keeping the play’s gears in motion, but the impending arrival of Jonah’s brother Liam promises to raise the stakes. Daphna is furious at Liam (Michael Steinmetz) for skipping Poppy’s funeral to go skiing in Aspen with his girlfriend Melody (Christy Escobar).

Also, she wants Poppy’s gold necklace, inscribed with the Hebrew word for “life,” which he carried through the Holocaust. As it happens, Liam intends to propose to Melody with the same necklace.

Murmurs passed through the audience as Liam and his blonde, blue-eyed girlfriend entered. A strong-willed and hardheaded Daphna finds her match in Liam, and from the moment he walks in, the two bicker. She harangues him for missing the funeral; he sneers at her religiosity; she mocks his doctorate in “contemporary Japanese youth culture” and his pert, goyish girlfriend. The stage is set for an epic showdown.

When the men leave for some fraternal bonding, Daphna doesn’t disguise her skepticism of Melody, whom she proceeds to interrogate. The result is an incredible comic bit that touches on Melody’s calf tattoo of a treble clef and moves on to her cultural heritage. Daphna asks what the derivation of the name Melody is, to which Melody replies, “Caucasian.” Prodded about where “her people” are from, Melody offers “Delaware,” setting Daphna on a tirade that ends with: “I’m asking, where did your family come from before they came to Delaware to perpetrate genocide?” It’s a warm first impression for the future in-laws.

(Full disclosure: My dad is Jewish and my mom, originally Episcopalian, is from Delaware. The older woman sitting next to me had recently lost her father, known as Poppy, who had willed his gold “Chai” necklace to a grandchild. We agreed that between us, we could have written the play.)

When the brothers return, Daphna and Liam’s antagonism explodes into a full-fledged screaming match, and the play becomes a glorified exchange of insults. Liam’s five-minute-long verbal takedown of Daphna met with the audience’s sustained applause. When Daphna has her turn to retort, she accuses him of being a self-hating Jew who preys on bimbos.

The male characters’ apathetic, teenage-y mode of social interaction rings true but doesn’t make for gripping theater. The women are more dynamic and fortunately get the lion’s share of stage time.

Everything builds toward the most dysfunctional marriage proposal imaginable, but the play’s underlying tensions over the family’s property and heritage find no real resolution.

Liam and Daphna both command sympathy: Shouldn’t he be free to marry the girl he loves? Isn’t she right to value her culture and religion? Their depth, the cousins’ grief and the recurring mentions of Poppy’s Holocaust experience lend the play moments of seriousness and elevate it above farce.

Does “Bad Jews” trade in stereotypes? Not more than any raucous comedy might. Besides, the characters feel substantial and unpredictable, even when they’re telling jokes and espousing big ideas. (Apparently you don’t have to be Jewish to appreciate “Bad Jews” — out of hundreds of audience members, I was the only one to laugh when Daphna sassily enunciated the Hebrew word for “sorry.”) Daphna and Liam may be bad Jews, but they’re also young people doing their best to grapple with the questions of growing up.