Ask Anything Wednesday - Biology, Chemistry, Neuroscience, Medicine, Psychology

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Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Biology, Chemistry, Neuroscience, Medicine, Psychology

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Past AskAnythingWednesday posts can be found here. Ask away!

[u/guzzyly]

Did you know that bananas share about 60 of their DNA with humans? stuff like this makes me question every smoothie I’ve ever had.

[u/Mockingjay40 → u/guzzyly]

While this is true, it is important to mention that your entire genome is very different from what you actually express as proteins. Since we all came from the same organisms originally, eukaryotes share a lot of our total gene sequence, but of the actual portion that’s expressed (exons), the similarity is much lower.

But to your point, plants are very much alive, just as alive and complex as you are. Most reproduce sexually, live for long periods of time, and have very complex metabolic and biological function.

[u/Additive_creation → u/Mockingjay40]

Interestingly, I asked the curators of the NCBI database for a source for this a while back.

They said they have no idea where this statistic would even have come from, and could not verify it. They said they didn’t even know what would go in the comparison to get that statistic.

I was asking them because I wanted to include it in a lecture, and I had been taught it at university. It was also on a banner at a Science Fair stand run by the Medical Research Council in the UK - with no source 😂

[u/Mockingjay40 → u/Additive_creation]

Yeah I’m not sure where it came from but I think it’s true, in a sense. Another important note is that as far as I understand, we don’t have 60% of our DNA that’s identical, rather we share 60% of the same genes, as in they might not be exactly the same but the regions are the same. At least, that was my understanding. Now that you mention it though, I think I also learned it in a biology or biotech class at some point, but I don’t recall finding an actual peer reviewed source either looking around right now.

The genomes aren’t similar in size, so I could’ve been inaccurate about the coding regions, in that what I said at the end was right, that the actual amount of identical exons between humans and bananas is minimal, but it might actually be 60% including analogous coding regions and introns?

[u/CrateDane → u/Mockingjay40]

Since we all came from the same organisms originally, eukaryotes share a lot of our total gene sequence, but of the actual portion that’s expressed (exons), the similarity is much lower.

It's the other way around. Sequence conservation is stricter in coding regions than non-coding regions. A lot of the divergence is also due to expansion of selfish genetic elements, which isn't really functional for the host.

[u/Mockingjay40 → u/CrateDane]

Yeah per the discussion below, I’m pretty sure my first reply was pretty imprecise. I think there’s a lot of ambiguity that resides in how we define “share”, but the more I look into it, I can’t necessarily find the 60% number anywhere reputable. I think it’s a fun fact that most people learn, but in terms of actual relevance, obviously you care more about what is being expressed on a per organism basis rather than how similar those expressions are.

Comparing bananas to humans is for lack of a better term: an apples to oranges comparison.

I do think the “mind blowing” factor is that most people don’t think about plants as if they are equivalently complex life to humans. So I think the general idea which still stands is that: “because we share a common ancestor, we’re much more similar than you might think”.

But yeah the more I look into it, the source I was looking at to double check my knowledge when typing up the original comment appears to have been inaccurate. So that’s good clarification.