It is discovered that a character, or a baby, has a parent whose identity is not known. Solution? Get a DNA test. Prove beyond [[MamasBabyPapasMaybe a reasonable doubt]] who the father really is, and proceed from there. All the other guys who aren't the dad can go home. Well, unless the real daddy is a GlorifiedSpermDonor and the fake one has actually been there for the kid their whole life. In which case, go take a hike sperm daddy.

This trope can also occur with mothers, but that's a much rarer occurrence (barring a babynapping, a switcheroo with a different newborn, or a delivery while the woman is unconscious, the mother knows the baby she just birthed is her own). This test can also be used indirectly to link siblings together. In any case, how long it takes for the DNA test to get finished typically depends on the speed of the [[TravellingAtTheSpeedOfPlot plot]]. The DNA test is not infallible: if the bad guys know about the test, they may attempt to keep the [[StatusQuoIsGod Status Quo]] by altering the test results (of course, they must [[KeepingSecretsSucks force other characters into secrecy]] about that, and in any case [[TheReveal it won't last for long]]). It is also subject to TheCSIEffect, as the test may be inconclusive if the the potential fathers are closely related (especially brothers), since they already share many of the same genes.

May result in a SurpriseIncest, if the character was in a love relation with an offspring of the man who turned out to be the father.

Almost always happens at some point after a LukeIMightBeYourFather revelation. Also happens if a woman decides to have MySecretPregnancy. The TropeBreaker for MamasBabyPapasMaybe.

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!!Examples:

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[[folder:{{Anime}}]]
* Very irritatingly avoided in ''OnegaiTwins''. They explain that it "costs too much money"... the episode before they win a lot of money and blow it on a HotSpringsEpisode.
* In ''Anime/MobileSuitGundamWing: Endless Waltz'', Mariemaia claims that Treize being her father has been confirmed through DNA testing. We never actually see the results of the test though, and there is considerable doubt on Mariemaia's parentage all the same.
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[[folder:Comic Books]]
* In a story arc in ''Franchise/{{Batman}}: Gotham Knights'' had the villain Bane discovering evidence suggesting that his real father was an American doctor, and, as the doctor has died, seeking a DNA matching test with the doctor's son -- Bruce Wayne.
* A variation in ''ComicBook/HelOnEarth'' When Franchise/{{Superman}} puts his battle-suit on ComicBook/{{Superboy}}, the [[ChestInsignia family crest]] should have changed the instant it identified his Kryptonian bloodline. It stayed the same, confirming Superman's suspicions that Superboy's his clone.
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[[folder:{{Film}}]]
* Done in ''Film/{{Elf}}'' to confirm that Buddy is Walter's son.
* The SoBadItsGood movie ''Une chance sur deux'' (Half a Chance): Alice gets a DNA test to find out who her real father is [[spoiler: but she likes the two possible dads so much that she throws away the results.]]
* In ''WesternAnimation/{{Ratatouille}}'' to see if [[spoiler:Linguini is Gusteau's son.]] The testing hit a slight snag when the first sample was identified as "rodent".
* ''Film/BabyMama'' actually has the inverse with a court ordered maternity test. The premise of the movie was that a surrogate mother is artificially impregnated using the other woman's egg and her own husband's sperm. The test is because she has the child rather late after the egg was inserted and it's unclear who the biological mother is.
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[[folder:{{Literature}}]]
* Plays an important role in the ''Literature/AdrianMole'' series, where a DNA test reveals that Adrian is the father of Glenn Bott, and later that his sister Rosie [[spoiler:is the daughter of their mother's ex-lover Mr Lucas.]]
* The ''Literature/TalesOfKolmar'' series takes place in a medieval world, but it's apparently possible for a demon to confirm who someone's father is.
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[[folder:LiveActionTV]]
* Used to establish that [[spoiler: Christian is the father of Matt]] in ''Series/NipTuck''.
* Series/{{House}} gets a DNA test after his father's funeral, proving that they're not related.
** One episode revolves around House going to great lengths to prove that his patient's father is not the real father and gets both the parents tested. [[spoiler: Turns out both aren't his biological parents and he's adopted.]]
** Another episode has House trying to prove that at least one of Taub's kids isn't his.
* The titular heroine of ''Series/VeronicaMars'' suspects at one point that her real father is her ex-boyfriend Duncan's dad, so she runs a paternity test, which [[UnReveal she shreds without reading]], deciding she doesn't need to know. Later in the season, Keith Mars has his own test done, [[spoiler:which confirms that he is, after all, her real father]].
** Also done, though not with a DNA test, with Trina Echols, who was adopted. Trina claimed publicly that she needed a bone marrow transplant to smoke out her real parents. Her mother came forward. Her father was a JerkAss.
* Dorothy and her mom from ''Series/TheGoldenGirls''.
* Sidney and Jack Bristow from ''Series/{{Alias}}'' had to go through this due to speculation that Sidney's biological father was actually Sloane. [[spoiler:Turns out Jack is her real father]].
* In ''Series/MyTwoDads'', ''the dads'' throw away the results, but they needed a little persuading.
* Often featured on sleazy daytime shows like ''The JerrySpringer Show'', where it's used to determine whether a woman was cheating on her boyfriend/husband with another man or to prove that a man is the father of a child when he denies it.
* These days every other episode of ''Series/{{Maury}}''.
** Led to a CrowningMomentOfFunny when a young mother brought no fewer than a half dozen possible fathers onto the show for testing. After a long drawn-out process of discussing her lifestyle and her complicated parenting situation, the results come back and...'''none''' of them are the father! Like a pack of hounds, all the tested would-be fathers round shouting at the girl. ''"There's even more?!"''
* These days at least once an episode on ''The Jeremy Kyle Show''.
* In ''Series/UglyBetty'', Daniel Meade receives a letter telling him he is the father of Daniel Jr., the child of a French model he met years ago on a business trip. The paternity test reveals [[spoiler:that Daniel Jr.'s father is Alexis Meade, now Daniel's sister.]]
* In the ''Series/{{Monk}}'' episode "Mr. Monk Gets a New Shrink," Dr. Kroger is revealed to have a stormy relationship with his son Troy. Namely, because Troy has made him take three paternity tests because he didn't believe they were related. Also, Randy has arrested Troy on at least one or two previous occasions.
* ''Series/ItsAlwaysSunnyInPhiladelphia'' averts this--Charlie is, more likely than not, Frank's son, but Frank refuses to have the DNA test.
* A staple of Soap Operas. Count on someone to conceal and/or falsify the results.
* Used on ''Series/LoisAndClark'' when a little boy displayed Kryptonian powers. The boy's mother claimed that Superman was the father, while a shocked Superman protests that he's never seen her before, let alone slept with her. One guy claimed the test wasn't needed, it must be obvious that Superman is the father. [[spoiler: The boy was human, and the super powers had been transferred to him.]]
* In ''Series/MyNameIsEarl'', Earl has Dodge and Earl Jr.'s DNA tested to find out who Dodge's real father is. [[spoiler: It turns out it was him all the time. Earl and Joy conceived Dodge at a Halloween party. It's also revealed that Earl Jr.'s real father is ''not'' Darnell as was previously thought. It's never revealed who his father actually is.]]
* In an episode of ''Series/{{Smallville}}'' a woman appears who thinks Clark is her son and demands a DNA test. Clark gets his SecretKeeper Pete to donate a DNA sample after breaking into the lab, so the results won't reveal that Cark isn't human.
-->'''Pete:''' Man, this "Mission Impossible" stuff is great. But other than my scintillating conversational skills, I still don't understand why you brought me along.
-->'''Clark''' I need your spit.
* ''Series/{{Dexter}}'' has a DNA test done to confirm that the man whose house he inherited was really his birth father.
* Done confusingly on ''Literature/GossipGirl'' in season three with Elizabeth who claims to be Chuck's (supposedly dead) birth mother. Chuck gets a DNA test which proves that she is his mother, but it's implied that the results were tampered with by his [[EvilUncle Uncle Jack]]. As of season four we still haven't found out for sure whether or not Elizabeth is his mother.
* Parodied on ''{{Dinosaurs}}'': due to a mix-up, it's suggested that the Sinclairs accidentally got another family's egg (the one that hatched into Baby) while the other family got theirs. Earl and the other father are subjected to battery after battery of bizarre tests (including a centrifuge)... and then the doctor just takes the blood test anyway. The test said the eggs were switched but it was later revealed it was a mistake.
* Warrick got one on ''{{CSI}}'' just before his death, as part of his attempt to gain custody of his infant son. His colleagues only discover this when they find the test results while retrieving clothes to bury him in.
* High-tech alien version occurs in the series finale of ''{{Series/Farscape}}''. The fact that Aeryn needs to find out who her baby's daddy is forms a major theme of the final series.
** Earlier, Aeryn is convinced that an alien is her long-lost father via high-tech DNA test. [[spoiler: The test results were actually faked.]]
* ''BostonLegal'': A man who was born out of artificial insemination was dating a woman who was born the same way and they were afraid of being [[BrotherSisterIncest half-siblings]]. To learn if they had the same father or not, they sued the lab to force them to tell because a DNA test using only the couple's blood would be inconclusive if they were half-siblings or complete strangers.
* On ''{{NCIS}}'', Abby tests her DNA against the DNA of the woman that she thought was her mother and finds out that she's adopted.
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[[folder:WebComic]]
* ''BatmanAndSons'' mentions that Bruce is taking care of baby Terry, but not baby Damien, because [[spoiler: Catwoman]] thought to do a DNA test before handing over her kid, whereas Talia did not.
* Played with on ''SomethingPositive'', in which a DNA test reveals that Davan is not the father of an ex-girlfiend's son, but Davan and the son bond anyway.
* A [[http://www.harkavagrant.com/index.php?id=272 Victorian version]] on ''HarkAVagrant''. (Fourth down)
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[[folder:WesternAnimation]]
* When Homer on ''WesternAnimation/TheSimpsons'' wanted to know if his dad was Abe or a lifeguard named Mason Fairbanks. [[spoiler:He wasn't, but Abe switched the labels because Homer seemed too interested in Fairbanks.]]
* In one episode of ''TheBoondocks'', Granddad Freeman goes on a talk show where a DNA test reveals he has a long-lost son. [[spoiler:Except the host lies about the test results on camera, only putting a disclaimer in the credits. The man's real father is Billy Dee Williams.]]
* In ''WesternAnimation/{{Gargoyles}}'', [[MadScientist Dr. Sevarius]] does a DNA test on [[AffirmativeActionGirl Angela]] (against her will) and happens to discover that [[TheHero Goliath]] is her biological father. This shocks her and winds up causing some drama, since Goliath follows the gargoyle tradition where biological relationships aren't important.
* In ''WesternAnimation/SouthPark'', Eric Cartman had no idea who his father was. Neither did his mother considering the number of possible candidates so a blood test was taken. It was then revealed his father was [[spoiler:his "mother", who was actually a hermaphrodite who had a penis (much to the disgust of the men who only learned when Dr. Mephisto brought it up) and impregnated some woman. Cartman briefly asked who his real mother was, much to the horror of the men who believed they could have been his Dad, but, once Ms. Crabtree the school bus driver, Principal Victoria and the Mayor of South Park were introduced as options, Cartman decided he didn't want to know.]]
** Of course many many seasons later it was revealed that [[spoiler: The whole thing was a ruse, Cartman's mother is actually biologically female, and Cartman's father is Scott Tenorman's father, who Cartman had killed and tricked Scott into eating in a bowl of chili]].
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