Speaker 1: Welcome to brain Stuff production of I Heart Radio. Hey
Speaker 1: brain Stuff, Lauren fog Obam. Here, during party conversation or
Speaker 1: at a trivia night, you may have heard the fun
Speaker 1: little fact that humans and bananas share fifty or even
Speaker 1: six of the same DNA. There seems to be a
Speaker 1: lot of differences, though, between a person and a piece
Speaker 1: of yellow fruit, starting with the fact that one is
Speaker 1: an animal and the other as a plant. But actually
Speaker 1: there is some truth to that startling statistic, but it's
Speaker 1: not the whole truth. This urban legend of sorts likely
Speaker 1: originated from a program run by the National Human Genome
Speaker 1: Research Institute back in although similar data may have been
Speaker 1: run elsewhere. Genetics expert Dr Lawrence Brody and his colleagues
Speaker 1: generated some banana human information to be included as part
Speaker 1: of an educational Smithsonian Museum of Natural History video called
Speaker 1: The Animated Genome. That video noted that DNA between a
Speaker 1: human and a banana is forty one percent similar. In
Speaker 1: order to find out how this similarity was determined, we
Speaker 1: talked with Dr Brodie himself. He explained that first, it's
Speaker 1: important to understand the difference between DNA and protein products.
Speaker 1: You can think of DNA as the blueprint of a house,
Speaker 1: and protein products as the actual house because all of
Speaker 1: the information is in there. Then think of human DNA
Speaker 1: as the blueprint for a ranch home, and banana DNA
Speaker 1: is that of a condo. In each house, a bunch
Speaker 1: of things are similar the plumbing, bathrooms, kitchen, but the
Speaker 1: end products are both quite different. And that's how it
Speaker 1: works with humans versus just about everything else from bananas
Speaker 1: two chimpanzees. The second thing to keep in mind is
Speaker 1: that genes, which are the regions of DNA that code
Speaker 1: for these proteins, only make up about two per cent
Speaker 1: of your DNA. In order to compare humans and bananas,
Speaker 1: scientists first looked at the sequences of genes in a
Speaker 1: typical banana gino. Brodie said. We then used these DNA
Speaker 1: sequences to predict the amino acid sequence of all the
Speaker 1: protein means that would be made from those genes. We
Speaker 1: then did the same process for all human genes. All
Speaker 1: of the protein sequences were placed in a file. Next,
Speaker 1: the scientists compared the protein sequence from each banana gene
Speaker 1: to every human gene. Brodie said. The program compares how
Speaker 1: similar the sequence of the banana genes are to each
Speaker 1: human gene. Program kept any matches that were more similar
Speaker 1: than one would expect by chance. The program continued doing
Speaker 1: this gene by gene. All told, more than four million
Speaker 1: comparisons were done, resulting in about seven thousand best hits
Speaker 1: between the two genomes. Then the percent similarity score for
Speaker 1: each of those hits was averaged. Bertie said, this gave
Speaker 1: us the result of about this is the average similarity
Speaker 1: between proteins gene products, not genes. Gene products or proteins
Speaker 1: are the biochemical material resulting from a gene becoming functional.
Speaker 1: Brodie continued, Of course, there are many many genes in
Speaker 1: our genome do not have a recognizable counterpart in the
Speaker 1: banana genome, and vice versa. In case that's a bit
Speaker 1: difficult to chew and swallow, let's break it down. Essentially,
Speaker 1: they took all of the banana genes and compared them
Speaker 1: one at a time to human genes. From that they
Speaker 1: called a degree of similarity. If the banana had the
Speaker 1: gene but the human didn't, that didn't get counted. And
Speaker 1: about sixty of our genes have a recognizable counterpart in
Speaker 1: the banana genome, Brodie explained. Of those, the proteins encoded
Speaker 1: by them are roughly identical. When we compare the amino
Speaker 1: acid sequence of the human protein to its equivalent in
Speaker 1: the banana. It may seem shocking that so many genes
Speaker 1: and so many of the proteins that they create are
Speaker 1: similar in two such vastly different beings as a person
Speaker 1: in a banana. But when you think about it, it's
Speaker 1: not that shocking, Brodie explained. If you think about what
Speaker 1: we do for living and what a banana does, there's
Speaker 1: a lot of things we do the same way, like
Speaker 1: consuming oxygen. A lot of those genes are just fundamental
Speaker 1: to life. So when people repeat the percentages being a
Speaker 1: similarity of DNA, actually what the research looked at was
Speaker 1: the similarity of gene products, Brodie reassured us, it's a
Speaker 1: pretty minor mistake. The kernel that you would take home
Speaker 1: is that we have something in common with a banana
Speaker 1: and a potato and a pine tree. That part is true.
Speaker 1: The fine point about the gene products or the DNA,
Speaker 1: it's easy to see how that would get translated incorrectly.
Speaker 1: So a scientist looked at the DNA sequence of a
Speaker 1: banana and compared it with the DNA of a human
Speaker 1: it would not align. We also spoke via email with
Speaker 1: Mike Francis, a PhD student in bioinformatics at the University
Speaker 1: of Georgia. He explained, you share fifty of your DNA
Speaker 1: with each of your parents, but with bananas, we share
Speaker 1: about of our genes. As we said earlier, genes make
Speaker 1: up just two of your DNA, So what's the other
Speaker 1: made up of? Well eight percent of the rest of
Speaker 1: your DNA regulates genes as to whether a gene should
Speaker 1: be turned on or off. The other appears to have
Speaker 1: unknown functions or functions that have been lost through evolution.
Speaker 1: Francis said, these unknown sections of DNA used to commonly
Speaker 1: be called junk DNA because it was thought to do nothing.
Speaker 1: I hesitate to use the phrase junk DNA because each
Speaker 1: year it seems we realize more of this junk is
Speaker 1: actually functional. Humans don't just share a high percentage of
Speaker 1: protein and coding genes with bananas. We also share of
Speaker 1: those genes with a mouse, and we share sixty one
Speaker 1: of disease causing genes with a fruit fly. Brodie said,
Speaker 1: the remarkable thing is that despite being very far apart
Speaker 1: in evolutionary time, we can still find a common signature
Speaker 1: in the genome of a common ancestor. These are preserved
Speaker 1: because the genome of an organism that lived billions of
Speaker 1: years ago contained genes that helped cells live and reproduce.
Speaker 1: Those same genes are preserved in us and plants. Francis
Speaker 1: add that humans likely share about one percent of their
Speaker 1: DNA with other fruits as well. He said this is
Speaker 1: because all life that exists on Earth has evolved from
Speaker 1: a single cell that originated about one point six billion
Speaker 1: years ago. In a sense, we're all relatives. Today's episode
Speaker 1: was written by Alia Hoyt and produced by Tyler Clay.
Speaker 1: Brain Stuff is the production of iHeart Radio's How Stuff Works.
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