What it means to share DNA with other organisms

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We share 60% of our DNA with bananas, but we are clearly not 60% banana.

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We are 60% banana, and banana is roughly 60% human. It’s just that the other 40% is enough to differentiate us from a banana.

When we say we share 60% of DNA with a banana, it means when you sequence out our DNA and a banana’s DNA, 60% of them match

DNA fundamentally is instructions to make proteins. A lot of the basic proteins needed for cells to function (build cell membranes, move things around, tie themselves in place, etc) are going to be the same even in very different organisms. As a result, pretty much any multicellular organisms are going to share a lot of DNA, because the instructions needed for the basic building blocks of cells are the same.

DNA is just a recipe on what proteins to make, how to build a cell, etc. That’s common between all life on earth. And 20% is still a lot of difference. That 20% includes all internal organs, 5 fingers and toes, backbone, eyes, etc. Again things that are shared with most (land) chordates. So by the time you get to chimps and humans, there’s only a 1-3% difference in DNA.

DNA contains the instructions for making proteins, which are very important molecules in biology that generally do most of the “heavy lifting” of keeping things running. Basically every living thing we have encountered so far is made of cells that all have roughly the same fundamental components, which means a ton of the same proteins are used for general functions like moving food around the cell, breaking down sugars, controlling cell division signals, etc., regardless of if you are a yeast cell or a plant cell or a human cell.

You can think of it kind of like Lego pieces shared between the Death Star set and a soccer stadium set. They are two very different structures, but they are both going to use a ton of the 2×2, 2×4, and other super common brick types (but maybe different colors). By shape alone, it’s very possible 60% of the brick shapes in one set are also found in the other set.

DNA is basically the instructions manual for life. Think about if you are building with legos and each block is a strain of DNA. Whether you are building a train or a plane, there will be some blocks and steps will be the same. That’s the similarity of the DNA. The different blocks and steps is what gives you a train vs a plane or a human vs a banana