Top 5 Myths About DNA (CS14)
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Top 5 Myths About DNA (CS14)


This week on Cracked Science: just because
something is popular doesn’t mean it’s well understood. Case in point: DNA. [TITLE] Hey, this is Jonathan Jarry and you’re watching
Cracked Science, the show from the McGill Office for Science and Society that separates
sense from nonsense on the scientific stage. DNA has become an important part of our discourse. DNA can be used to exonerate; to alter crops;
to potentially cure diseases; and to show white supremacists that they really
did come from Africa after all. It is undeniable that there is an appetite
for DNA and the power that it evokes. Last year, AncestryDNA sold roughly 1.5 million
of their straight-to-consumer DNA kits, and that’s just over the American Thanksgiving
weekend! That led Wired reporter Megan Molteni to write,
“That’s like 2,000 gallons of saliva-enough to fill a modest above-ground swimming pool
with the genetic history of every person in the city of Philadelphia.” What gets lost in the Great Spitting of 2017
is that interest does not necessarily equate knowledge. There are many myths about DNA, and for good
reasons. Unless you’re extracting it, DNA is not something
that you see, and it’s not intuitive how it all works, how a long string of so-called
letters ends up coding for an entire organism. There’s something mystical about the molecule
of life, and that’s where our intuition can lead us astray. So, I want to knock down some of these myths
tonight, and I want to make sure I reach a lot of people and change a lot of minds. So, I’ve decided to combine the popular Buzzfeed
listicle format with the award-winning movie Three Billboards Outside Ebbing, Missouri
to create Cracked Science’s own Top 5 Billboards Outside
Coding, Missouri. If that doesn’t generate views, I don’t know
what will. [Billboard #5, Almost all food has DNA] There’s this idea that genetically engineered
food, commonly known as GMOs, has DNA but that non-engineered food doesn’t. And that’s just wildly wrong. Carrots contain DNA. Apples contain DNA. Brisket, milk, wheat flour, they all have
DNA. Most of what we eat, and drink, contains DNA,
because it’s made up of cells, which contain the molecule of life. There are exceptions: sugar, salt, water,
alcohol, highly refined substances which are extracted from foodstuff generally don’t contain
DNA. But most of what we eat, whether it’s genetically
engineered or not, contains DNA. And that’s always been the case. [Billboard #4, There’s no such thing as a
fish gene] When researchers were experimenting with a
tomato that would be more tolerant to frost, they added an antifreeze gene that came from
the winter flounder, and so the tomato was nicknamed “the fish-mato”. And it’s easy to imagine that the genes inside
of a fish have some sort of fish odour, or that all of these genes are specific to the
fish and have no business being inside a tomato. But if we take 2 seconds to remember “Biology
101”, we know that, for example, humans and chimps share up to 98.8% of their genes, depending
on how you count. While we may want our genes to contain some
mystical essence of humanity, that’s just not what they do. Genes are discreet stretches of DNA that code
for a protein, and proteins play a number of roles in our bodies. For example, the Hox proteins made by the
fruit fly will help guide its development to make sure its mandibles, antennae, thorax
and abdomen all grow in the right order. But because HOX genes are conserved across
so many species, you can remove one of them in fruit flies and replace it with a chicken
HOX gene and the fly develops just fine. Surprisingly enough, the outcome of this real-world
experiment had nothing in common with the little-known David Cronenberg sequel, The
Fly 3: Chicken Little’s Terrible, Horrible, No Good, Very Bad Day. There’s no such thing as a fly gene, a tomato
gene, or a human gene. Just like you could use a yellow LEGO to make
Bowser, you can use that same yellow LEGO to make Pikachu. [Billboard #3, You don’t have the “gene for”
Huntington’s disease; it’s a mutation] On so many TV shows, I hear characters sighing
with relief as they learn they don’t have “the gene for” this or that disease. What this sounds like is that someone with
Huntington’s disease, for example, has a whole gene whose sole purpose is to give them this
disease, whereas healthy individuals don’t have this gene and instead have, I guess,
an empty space in its place. It’s sort of the “gene of the gap” argument,
I suppose. We all have this gene. It’s called the Huntingtin gene, and it happens
to have a repeat of three letters, CAG, over and over again. People who have the disease have a longer
stretch of this repeat, as if someone was copy/pasting the repeat and dozed off for
a few seconds while hitting “Control-V”. A gene’s purpose is not to cause disease. The gene codes for a protein that has a specific
job to do inside your body. For instance, the gene associated with Duchenne
muscular dystrophy codes for a protein that normally connects a muscle fibre to its surroundings. When it’s mutated, the protein can’t do its
job, and that’s what causes the disease. [Billboard #2, It’s often more complicated
than just 1 gene=1 disease] I have given very simple examples so far,
with Huntington’s disease and Duchenne muscular dystrophy, where a single gene is mutated
and that leads to a disease. And when genetics was just getting started,
this was the thinking, that each disease has a single gene behind it. We now know that, as with Taylor Swift’s Facebook
relationship status, it’s a lot more complicated than that. Really common diseases, like asthma, tend
to be caused by mutations in more than one gene. Then there’s cancer. While there are single mutations that predispose
you to developing certain forms of cancer, we know that cancer is an accumulation of
many mutations in many different genes, and some of these mutations are known as driver
mutations: they are needed to occur to drive the cancer forward. On average, breast cancer needs 4 of these
mutations, whereas colon cancer needs 11. But even with simple traits, like hair and
eye colour, we are far from the “one gene, one trait” rule. These are the known genes involved in creating
the particular shade of hair colour you have. Some physical traits and diseases are caused
by variations in one gene. But for many, it’s the shared responsibility
of a whole bunch of them. And, finally, billboard #1, [Spending 250$ on a DNA kit to find out if
you have a unibrow is totally worth it-] No, sorry, that’s not it. [Billboard #1, Astronaut Scott Kelly’s genes
were not altered after spending a year in space] Despite what you may have read online, it
wasn’t that Scott Kelly’s genes were mutated by his space travel, but rather that their
expression was different, and when I tell you what this means, you’ll realize that it’s
nowhere near as spectacular as some media outlets made it out to be. You see, genes make proteins, but genes aren’t
*always* making proteins. It’s like a bread maker making bread: they
make baguettes and ciabattas during the day, but they sleep at night. Before a big holiday, they may get an increase
in customers and they have to work longer and make more bread. It’s the same situation with a gene: how much
protein it makes depends on a number of factors, and that’s known as the “regulation of gene
expression”. The levels of your hormones can affect gene
expression; the drugs you’re taking can do the same; the
amount of oxygen you’re getting; the viruses you catch; whether or not you
smoke; all of these things can affect… well, how
much bread your bread maker makes. Gene expression can be influenced by a number
of factors, so it’s no surprise that spending a year in space-in a microgravity environment,
with disrupted sleep patterns and a diet that does not exactly scream Michelin stars-had
a significant impact on Kelly’s gene expression. So, to recap, most of what you eat has DNA; genetic engineering did not violate the essence
of your tomato; nobody has “the gene” for a particular disease; genetics is often complicated; and going to space will not turn you into
a lizard creature, unrecognizable by your twin. And as a final bit of DNA debunking, when
scientists take a gene from one species to put it into another, it looks nothing like
this deleted scene from David Cronenberg’s The Fly, in which Jeff Goldblum tries to fuse
a cat to a baboon. My recommendation this week is for a book
I haven’t yet read, but if it has anywhere near the richness and delectability of the
author’s first tome, it’s worth a read. I’m talking of course of Dr. Siddhartha Mukherjee’s
The Gene: An Intimate History. Mukherjee’s freshman effort, The Emperor of
All Maladies, was a fascinating and exhaustive history of how we came to know what we know
about cancer. In The Gene, the Pulitzer-prize-winning author
turns to genetics. From Darwin to the double helix, from the
influence of genes on IQ to the post-genome era, this book has it all. I can’t wait to dig into this 500-page mammoth
that was on the Washington Post’s 10 best books of 2016 list. If you want a deep dive on genetics, this
is it. This video series is one small part of what
our office does, so go to mcgill.ca/oss/ to see what else we do to help separate sense
from nonsense and do subscribe to our newsletter. You can follow me on Twitter at cracked science
and join us next time for science that may or may not be all it’s cracked up to be.

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