Only Point Two Percent Different

Here's normal human DNA, and here's the DNA of the monsters we're fighting. My God! it's only 0.2% different! Despite the fact that the monsters have unexplainable powers, and look, act, and think almost nothing like us, there's no real difference between us and them! Really makes you think who the real monsters are, doesn't it? A subtrope/sister trope of What Measure Is a Non-Human?.

In Real Life, it is true that we share some portion of our genome with many other species. Hell, humans have specific genes that are pretty much the exact same as plants. According to most scientific theories, this is because all organisms are descended from the same progenitor organism species, which also used DNA, the universal genetic code. Some experts theorize that the first species may have used RNA, which was later used to code for DNA. The genes that were present in that original organism are still around, since they generally serve very important purposes in controlling different aspects of development, but those aspects that they control have been changed and co-opted into other pathways over time. So genes that function to pattern flower growth in some plants (determining which parts of a bud turn into petals, stamens, etc) are necessary for directing heart development in humans.

Further, DNA codes for chemicals, specifically proteins. Given that, and given that there are only so many ways to, say, break down a fat molecule into energy, it's hardly surprising that two wildly different animals, such as a mosquito and an elephant, would have large quantities of DNA (or rather, code for various chemicals needed for life) in common.

Keep in mind that when people who know something about genetics talk about differences or similarities within the same species, they may be ignoring the large percentage of genetic material they would by definition already have in common by being the same species.

Anime and Manga

 * The Angels in Neon Genesis Evangelion.
 * Though the reasoning for this is a bit sketchy. According to Ritsuko, the Angels are made of Hard Light, and she found a strange sequence of Hard Light in the Angel's tissues. Which for some reason she decided to compare to the human genome and came up with this trope.
 * The androids from Armitage III are ranked according to how human they are. "Firsts" are basically non-human robots, "Seconds" are androids, and the "Thirds" are so close to human they can get pregnant. And yes, they can reproduce with a human.
 * The androids aren't numbered base on how close they are to humans though, they are numbered based on their order of creation. The "Firsts" are created first, followed by the "Seconds," then the "Thirds." The "Thirds" are very close to humans because they are more advance. The "Fourth" were modeled after plants and are arguable improved versions of natural plant life (such as trees that are capable of moving around.)
 * The Abh from Crest of the Stars. Enemy propaganda says they are living robots. Their own propaganda says they are a superior race of living art. In reality, other than blue hair, Unusual Ears and a different organ in place of their sinuses, they're still basically human.
 * They are far more advanced than the humans from Earth though and are quite arrogant about throwing their technology around in fight where they have overwhelming technological advantages. This is sorta true in real life; many people in more advanced countries do tend to think of themselves as a superior race even though, in the past, they may have been the ones who were less advanced.
 * The Zentraedi from Robotech.

Comic Books

 * Ultimate Spider-Man has a rather inaccurate example when Spidey encounters the new Scorpion...who looks just like him. He brings Scorpion to the Fantastic Four, and Reed finds that Scorpion's DNA is 94% similar to Spidey's. For comparison, that's how much humans and chimpanzees have in common DNA-wise. (Although, as noted above, he might be ignoring homo sapiens standard DNA, and only counting DNA that could be expected to vary from individual to individual.)

Film

 * The Doom movie had an additional chromosome that caused people to become demons.
 * Mission to Mars had a puzzle in the face on Mars involving human DNA.
 * This movie has several DNA failures. In that scene, a character says, "That DNA looks human!" while looking at a few base pairs. Out of a few billion.
 * And another scene in the movie has a character displaying his "dream woman" who, apparently, consists of only a few base pairs again.
 * The clones from Star Wars: Attack of the Clones
 * Lampshaded when three clones are alone with Yoda, Yoda explains that though their faces may be alike, through the force he can see their minds are as diverse as other human groups. Specifically, they are clones of Jango Fett.

Live Action Television
"House: Oxygen saturation is 94%, check her heart. Foreman: Her oxygen saturation is normal. House: It’s off by one percentage point. Foreman: It’s within range. It’s normal. House: If her DNA was off by one percentage point she’d be a dolphin."
 * Inverted on The Event. The people from the Inostranka crash have 2% different DNA from humans, and the president interprets this fact to mean that they're just like humans. His advisor informs him that they have less in common with humans than apes do. This is used as an argument that they don't deserve human rights, an idea which the president doesn't approve of.
 * Referenced on House:


 * The entire premise of ABC's one-season-wonder Prey was based on a killer strain of humanity with the same genetic variance from homo sapiens as exists between us and chimpanzees. Also, they were caused by global warming.
 * The idea being that a localized acceleration of global warming accelerated human adaptation to that phenomenon among a particular population, who then spread out in secret among the rest of humanity. The show named them Homo dominus.

Video Games

 * In a rare non-human example of this trope, Mass Effect 2 has, during the Collector ship mission, the discovery that
 * It is actually stated that they underwent extensive genetic modification and cyberization. Of course, the point is moot in that . What those statues were in Mass Effect 1, however, is still a mystery.
 * It is stated in one conversation in ME3 that those are from an even older race whose planet the Protheans used for their secret research outpost. The Reapers have been doing this for a long time, and the Protheans were just the last cycle (before this one).
 * Solid Snake and Liquid Snake are RetConned into being 0.2% different in Metal Gear Solid 4, to explain why Snake's FOX-DIE infection isn't killing him. This leads to plot holes seeing as 0.2% difference is actually significantly larger in genetic terms than the practical difference between Solid and Liquid (who are identical twins).
 * Lan and MegaMan have a 0.1% difference in their DNA, due to MegaMan . However,

Western Animation

 * In the Harley Quinn cartoon, this is subverted. In his efforts to find a cure for his wife's condition, Mr. Freeze has been using the "common snow rat" as test subjects, claiming that snow rats and humans share 98% of the same genes. However, the bin with hundreds of dead snow rats (not to mention the terror expressed by the living ones in his lab) show he's not having much success at all. He now claims he's "98% certain that the 2% difference between genes is the reason I cannot succeed" and needs an actual human test subject. Naturally, this means Harley.

Real Life

 * In reality of course, there are fairly common cases of an additional chromosome. "Down's Syndrome" is actually one of the more benign duplicate chromosomes: in fact, only duplicate sex chromosomes are less harmful. A duplicate of any chromosome other than 21 or 23 drastically shortens your lifespan. Full trisomies of any chromosome other than 13, 18, 21, X or Y are incompatible with life, and cause miscarriage. Partial trisomies can be survivable however.
 * We share 75% of our known human disease genes with the fruit fly. (as well as daffodils) Which is awesome, as we can experiment on them and not on us. A particularly weird bit of experimentation showed that injecting the gene product of the PAX6 gene (which is found in humans and other animals and turns on eye development) into fruit flies caused eyes to develop (functioning like the insect's version, appropriately called eyeless). The eye that developed was still an insect compound eye though, as the proteins that are expressed as a result of the gene being turned on are still proteins specific to forming an insect eye, not a mammal's eye. Which goes to show how important that other 25% is in terms of genetics.
 * Genetically, mushrooms are closer relations to us than to plants.
 * Not just genetically. They also act a lot like us. For instance, they eat food, instead of photosynthesizing.