November 19, 2019 • 6 mins
You may have heard that people share about 50 percent of their DNA with bananas, and while there's a seed of truth to that, it's not quite right. Learn about our genetic similarity to fruit and other life forms in this episode of BrainStuff.
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Episode Transcript
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Speaker 1 (00:01):
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
(00:23):
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
(00:44):
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
(01:07):
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
(01:27):
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,
(01:50):
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
(02:13):
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
(02:35):
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.
(02:55):
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
(03:16):
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
(03:38):
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
(03:58):
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
(04:19):
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
(04:42):
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
(05:04):
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
(05:28):
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
(05:48):
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
(06:10):
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.
For more in this and lots of other topics that
are different but do similar things, visit our home planet
how stufe works dot com and for more podcasts from
(06:32):
my heart Radio, you can visit the I heart Radio app,
Apple Podcasts, or wherever you listen to your favorite shows.
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
(00:23):
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
(00:44):
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
(01:07):
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
(01:27):
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,
(01:50):
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
(02:13):
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
(02:35):
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.
(02:55):
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
(03:16):
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
(03:38):
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
(03:58):
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
(04:19):
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
(04:42):
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
(05:04):
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
(05:28):
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
(05:48):
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
(06:10):
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.
For more in this and lots of other topics that
are different but do similar things, visit our home planet
how stufe works dot com and for more podcasts from
(06:32):
my heart Radio, you can visit the I heart Radio app,
Apple Podcasts, or wherever you listen to your favorite shows.
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Ben Bowlin
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