Welcome to brain Stuff production of I Heart Radio. Hey brain Stuff, Lauren fog Obam. Here, during party conversation or at a trivia night, you may have heard the fun little fact that humans and bananas share fifty or even six of the same DNA. There seems to be a lot of differences, though, between a person and a piece of yellow fruit, starting with the fact that one is an animal and the other as a plant. But actually there is some truth to that startling statistic, but it's
not the whole truth. This urban legend of sorts likely originated from a program run by the National Human Genome Research Institute back in although similar data may have been run elsewhere. Genetics expert Dr Lawrence Brody and his colleagues generated some banana human information to be included as part of an educational Smithsonian Museum of Natural History video called The Animated Genome. That video noted that DNA between a
human and a banana is forty one percent similar. In order to find out how this similarity was determined, we talked with Dr Brodie himself. He explained that first, it's important to understand the difference between DNA and protein products. You can think of DNA as the blueprint of a house, and protein products as the actual house because all of the information is in there. Then think of human DNA as the blueprint for a ranch home, and banana DNA
is that of a condo. In each house, a bunch of things are similar the plumbing, bathrooms, kitchen, but the end products are both quite different. And that's how it works with humans versus just about everything else from bananas two chimpanzees. The second thing to keep in mind is that genes, which are the regions of DNA that code for these proteins, only make up about two per cent of your DNA. In order to compare humans and bananas, scientists first looked at the sequences of genes in a
typical banana gino. Brodie said. We then used these DNA sequences to predict the amino acid sequence of all the protein means that would be made from those genes. We then did the same process for all human genes. All of the protein sequences were placed in a file. Next, the scientists compared the protein sequence from each banana gene to every human gene. Brodie said. The program compares how similar the sequence of the banana genes are to each
human gene. Program kept any matches that were more similar than one would expect by chance. The program continued doing this gene by gene. All told, more than four million comparisons were done, resulting in about seven thousand best hits between the two genomes. Then the percent similarity score for each of those hits was averaged. Bertie said, this gave us the result of about this is the average similarity
between proteins gene products, not genes. Gene products or proteins are the biochemical material resulting from a gene becoming functional. Brodie continued, Of course, there are many many genes in our genome do not have a recognizable counterpart in the banana genome, and vice versa. In case that's a bit difficult to chew and swallow, let's break it down. Essentially, they took all of the banana genes and compared them one at a time to human genes. From that they
called a degree of similarity. If the banana had the gene but the human didn't, that didn't get counted. And about sixty of our genes have a recognizable counterpart in the banana genome, Brodie explained. Of those, the proteins encoded by them are roughly identical. When we compare the amino acid sequence of the human protein to its equivalent in
the banana. It may seem shocking that so many genes and so many of the proteins that they create are similar in two such vastly different beings as a person in a banana. But when you think about it, it's not that shocking, Brodie explained. If you think about what we do for living and what a banana does, there's a lot of things we do the same way, like consuming oxygen. A lot of those genes are just fundamental
to life. So when people repeat the percentages being a similarity of DNA, actually what the research looked at was the similarity of gene products, Brodie reassured us, it's a pretty minor mistake. The kernel that you would take home is that we have something in common with a banana and a potato and a pine tree. That part is true. The fine point about the gene products or the DNA, it's easy to see how that would get translated incorrectly.
So a scientist looked at the DNA sequence of a banana and compared it with the DNA of a human it would not align. We also spoke via email with Mike Francis, a PhD student in bioinformatics at the University of Georgia. He explained, you share fifty of your DNA with each of your parents, but with bananas, we share about of our genes. As we said earlier, genes make up just two of your DNA, So what's the other
made up of? Well eight percent of the rest of your DNA regulates genes as to whether a gene should be turned on or off. The other appears to have unknown functions or functions that have been lost through evolution. Francis said, these unknown sections of DNA used to commonly be called junk DNA because it was thought to do nothing. I hesitate to use the phrase junk DNA because each year it seems we realize more of this junk is actually functional. Humans don't just share a high percentage of
protein and coding genes with bananas. We also share of those genes with a mouse, and we share sixty one of disease causing genes with a fruit fly. Brodie said, the remarkable thing is that despite being very far apart in evolutionary time, we can still find a common signature in the genome of a common ancestor. These are preserved because the genome of an organism that lived billions of years ago contained genes that helped cells live and reproduce.
Those same genes are preserved in us and plants. Francis add that humans likely share about one percent of their DNA with other fruits as well. He said this is because all life that exists on Earth has evolved from a single cell that originated about one point six billion years ago. In a sense, we're all relatives. Today's episode was written by Alia Hoyt and produced by Tyler Clay. Brain Stuff is the production of iHeart Radio's How Stuff Works.
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