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Chiperoni t1_j9ztjfl wrote

Not in the sense I think you mean. Most physical characteristics are polygenic meaning different combinations of genes are interacting to give off a phenotype. So there's countless other combinations that can yield the same result. Even genes that are linked in all cases like blue eyes can have DNA changes at many different spots. Also outside of nature there is the just as important nurture.

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teoalcola t1_j9zxnsd wrote

If you were able to identify all the genes which determine their appearance and only compare those genes from both individuals, you would probably find very similar DNA. However, there are many other genes which determine other traits which are not directly visible (bone density, blood pressure, immune system etc.), and all those genes would most likely not be similar, so the overall DNA similarity would probably also be low.

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0oSlytho0 t1_j9zzsc0 wrote

Probably not. As in: most of our DNA is (near) identical but our phenotypic traits are determined by more than just the DNA. In a DNA test we don't look at the identical bits, we pinpoint for the more variable regions and repititions.

A funfact, there are animals that look very similar but are genetically extremely far apart. Different genes can result in similar traits in a completely different way. I can't remember the example my prof used in college but it was super interesting.

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DNA_ligase t1_ja04l1n wrote

Replying to 0oSlytho0 (#2,003,971)

Could you be remembering convergent evolution and analogous structures? It’s when two unrelated animals have similar ecological niches, so they end up adapting to it in similar ways. Like sharks and dolphins both having similar shapes and dorsal fins to swim in water, or echidnas and hedgehogs both having prickly spines.

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Unicorn_Colombo t1_ja0e23x wrote

Replying to whydontuwannawork (#2,005,504)

Yes. Phenotype is a function of genes. So p = f(g). Obviously, it depends on the function f. If the function was an absolute value, then g = 2 and g = -2 both will give you same phenotype 2.

Back from math and into biology, in many mendelic traits, which are traits where a phenotype depends on a single gene, the receive allele is simply an allele that does not produce a particular product, such as a pigment. Such as blue eyes, which are eyes that lack melanin (the eye colour is not a perfect example, as it turns out it is not exactly mendelian trait, but lets assume for simplicity it is).

Obviously, if a gene is not producing a certain product, a protein that is directly involved in some pathway, it is because it is "damaged" in some way. And there are many way it might be damaged. A protein might be produced, but it is non-functional, shorter, or the protein might not be produced at all. So many different mutations might be responsible for the same trait.

When we look at polygenic traits like height, we will see many different genes that are responsible for a small difference in height. When you plot the population phenotype, you might see a normal distribution. Consequently, assuming the same difference for every gene and 100 genes and an on/off effect of a particular gene, you can get a trait resulting from 50 genes in many way (something like 10^29 combinations).

On top of all this, traits depend on an environment. In the case of height, this is only a potential, you will benefit from your genotype only if you will have plenty of nutrition in your young age to reach this potential.

This difference between genotype and phenotype for polygenic traits, and the effect of an environment, is important when doing a selection in agriculture. Trying to find out how much of the trait is hereditary and how much it is determined by genetics gives you an estimate on how much you can influence the trait by breeding.

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Dorocche t1_ja0kz6b wrote

Replying to Chiperoni (#2,002,920)

This has happened, too

I remember reading about a man who was wrongfully convicted of a crime because the actual perpetrator was identical and had the same name. He was exonerated by DNA evidence years later.

I can't find that now though, so take it with a grain of salt; here's a similar fluff piece about baseball players instead:

https://nypost.com/2023/01/11/identical-strangers-with-the-same-name-and-job-took-dna-test/

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MissChievous8 t1_ja0nwgl wrote

I remember reading an article about 6 months ago regarding finding evidence of people who look the same share similar genetics despite not being related at all. Doppelgangers. They're apparently more likely to share lifestyle traits as well. Ive heard everyone has approximately 6 doppelgangers out there somewhere. Anyone met one of your own?

https://www.smithsonianmag.com/smart-news/doppelgangers-dont-just-look-alike-they-also-share-dna-180980635/#:~:text=Doppelg%C3%A4ngers%20share%20strikingly%20similar%20physical,%2C%20at%20least%2C%20siblings).

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greezyo t1_ja1vhux wrote

The honest answer is depends what you mean by similar and what you mean by related. If they are from the same family/ethnicity, then it's not impossible that they would share some genes that could cause similarities.

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ThrillSurgeon t1_ja2efh6 wrote

Replying to Hagenaar (#2,006,923)

Still, it probably is mathematically possible to a degree, but probably statistically in the domain of one solid object passing through another solid object because the subatomic particles lined up. Although, probably more likely than that.

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Kovaxim t1_ja2k2pn wrote

There was a case of some guy who either robbed a bank or murdered someone, can't remember.

The police had arrested the wrong guy, but couldn't know that as they looked as similar as twins and only a DNA test concluded who the culprit was.

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doc_nano t1_ja2weby wrote

It would be very easy to tell them apart genetically. The chances of anything close to the same genetics would be astronomically small, something like winning the lottery every day of an 80-year life.

However, they would likely be more similar to each other genetically than a random set of 2 human beings of the same gender and ethnicity.

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Quantentheorie t1_ja30pho wrote

Replying to HorizonBaker (#2,022,199)

Diet and environmental aspects do have an effect on things like aging and gene expression.

You could go prematurely grey or bald and end up looking quite different to your identical twin if your QoL standard varies a lot.

Its not entirely a non-factor.

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HorizonBaker t1_ja31bbz wrote

Replying to Quantentheorie (#2,023,066)

Okay, but is the fundamental shape and structure of your face changing? Sure if you gain weight you may gain weight on your face and vice versa, but the way you are raised isn't going to change how far apart your eyes are or how long your nose is.

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kidnoki t1_ja342iv wrote

Replying to Chiperoni (#2,002,920)

They actually tested this, a famous photographer Francois Bernell, searched the world to find "twins". These twins were people unrelated, but looked identical. They followed up the art project with a research experiment to look into their DNA and found that they actually did share more genetic material than the average person.

"Dr. Esteller found that the 16 pairs who were “true” look-alikes shared significantly more of their genes than the other 16 pairs that the software deemed less similar. “These people really look alike because they share important parts of the genome, or the DNA sequence,”

https://www.nytimes.com/2022/08/23/science/doppelgangers-twins-dna.html

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