If I share 50% of my DNA with a banana, does that make me half banana?
By Roberta
You might have heard from a friend or some quirky trivia question that humans and bananas share approximately 50% of the same DNA, how is that possible? When we look at it, there seems to be quite a difference between a person and a yellow fruit, starting from the fact that one is an animal and the other is a plant! Surprisingly however, there is some truth in that statement, but it is to be taken with a pinch of salt…
Let’s start from the beginning – how do we know this? Today we are capable of knowing all the genes that make up an organism or virus thanks to a technique known as genomic sequencing. This technique, invented by Frederik Sanger in 1977, allows us to see all the base sequences in an individual’s DNA and compare them to another or different organism, such as a banana! The latter is exactly what was done in 2013 by the National Human Genome Research Institute under genetics expert Dr. Lawrence Brody. The results however, which initially showed a 41% similarity, weren’t meant to be published, they were in fact supposed to be just part of a museum’s interactive video. Nevertheless, the findings appeared to be so shocking that people started talking and asking more questions: if I share 41% DNA with a banana, am I 40% banana? Since then, plenty more research has been done and the percentages changed slightly, but this question remained unanswered for many people.
So are we “whatever %” banana? The answer is no, not really, and here’s why. First, there is a difference between DNA and protein products, the latter are in fact what DNA is translated into to make us us, and a banana a banana. Dr. Brody’s way to simplify this is by thinking of DNA as the blueprint of a house, and protein products as the actual house. In other words, although every house has the same components (roof, plumbing, kitchen etc.) they don’t end up looking all the exact same. The same principle is true for humans and bananas, but also humans to chimpanzees and even human to human!
Next, although genes are important because as mentioned, they make us look and function the way we do, they only make up a very small percentage of our total DNA, only 2% in fact! So we only share approximately 50% of 2% of our total DNA… you do the maths, you’ll see it’s not much…
Finally, we need to understand how “similarity” was established in these experiments. Essentially, all the banana genes were deciphered and compared one at a time to human genes. Similarity was said to be present if the genes had a recognizable counterpart in the human genome, and if the banana had a gene that the human didn’t, that gene wouldn’t get counted. These results showed a 60% “similarity” between human and banana genes. Of that 60%, only 40% were found to be identical in terms of amino acid sequence and therefore protein products. That might still seem like a lot, but actually, it makes sense. The majority of those genes (and proteins) are likely to be involved in “housekeeping” processes such as consuming oxygen, producing carbon dioxide, and cellular division. So, as living beings, we mostly share genes that are absolutely necessary to survive!
In conclusion, because all life on earth has evolved from the same single celled ancestor billions of years ago, we will always share a percentage of our genes with any other organism that lives around us; this however, won’t make us 1/3, 1/2 or 100% them!
