From Bananas to Papayas: Genetically Modified Organisms (GMOs)

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DNA Decoded

66 calificaciones

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McMaster University

DNA Decoded

66 calificaciones

Are you a living creature? Then, congratulations! You’ve got DNA. But how much do you really know about the microscopic molecules that make you unique? Why is DNA called the “blueprint of life”? What is a “DNA fingerprint”? How do scientists clone DNA? What can DNA teach you about your family history? Are Genetically Modified Organisms (GMOs) safe? Is it possible to revive dinosaurs by cloning their DNA? DNA Decoded answers these questions and more. If you’re curious about DNA, join Felicia Vulcu and Caitlin Mullarkey, two biochemists from McMaster University, as they explore the structure of DNA, how scientists cracked the genetic code, and what our DNA can tell us about ourselves. Along the way, you’ll learn about the practical techniques that scientists use to analyze our genetic risks, to manipulate DNA, and to develop new treatments for a range of different diseases. Then, step into our virtual lab to perform your own forensic DNA analysis of samples from a crime scene and solve a murder.

De la lección

Manipulating DNA

In this module, we'll explore the techniques scientists use to manipulate DNA. Genetic engineering has allowed us to increase crop yields, diagnose illnesses, develop vaccines, and manufacture insulin. By carefully selecting a pair of molecular scissors (restriction enzymes), scientists are able to isolate a gene of interest and insert it into plasmid DNA, turning a common bacteria (E. coli) into a molecular copying machine. This week, we'll learn that mutations are genetic errors, but that not all mutations are necessarily bad — in fact, some mutations confer a selective advantage that protects against disease. We'll explain what genetically modified organisms are (and what they are not) and weigh in on the heated debates about the ethics and safety of GMOs in popular media.

Freaky Fruit: Manipulating DNA5:47

Slice and Dice: Restriction Enzymes10:47

Lights, Camera, Transformations6:31

Mutations, Mutations, Mutations!6:49

From Bananas to Papayas: Genetically Modified Organisms (GMOs)9:26

Conoce a los instructores

Caitlin Mullarkey
Assistant Professor
Health Sciences
Felicia Vulcu
Assistant Professor
Biochemistry and Biomedical Sciences

[Caitlin:] Wow! you've got more tomatoes than a soup factory.

Tell me you didn't make all of these by genetically engineering tomato genes.

[Felicia:] I didn't make any of these by modifying tomato genes.

[Caitlin:] They're amazing. You've got every colour:

yellow, red, green... [Felicia:] Do you see any blue tomatoes?

No. No, you do not.

[Caitlin:] So, you didn't do any genetic engineering to make these...

But they're every color -- except for blue. [Felicia:] I know. I just picked these

up at the farmers' market this morning. [Caitlin:] But all the varieties?

[Felicia:] Standard breeding procedures.

Just hybrid tomato plants made from cross-pollinating different varieties

[Caitlin:] Don't feel blue about it.

[Felicia:] Yeah, sure,

rub it in. [Caitlin:] Even this one?

[Felicia:] Exactly, even that one. Kumato. Hybrid.

Plain old boring hybrid. Big deal. [Caitlin:] Okay, so you're telling me there's

nothing genetically modified here? [Felicia:] Correct, no GMOs here.

[Caitlin:] Well, I'm surprised --

and also a bit confused. [Felicia:] That's understandable.

The term GMO actually gets thrown around a lot these days.

You hear the term GMO on the news all the time.

[Caitlin:] Three little letters and so

much controversy.

People seem to have strong opinions about this issue.

[Felicia:] Yeah, but no matter how you feel

about GMOs, it's important to grasp what they are and what they are not.

We will help sort that out for you now on... [Both:] DNA Decoded.

[MUSIC]

[Caitlin:] More arts and crafts I see?

[Felicia:] Well, no. This is about as close

as I'm going to get to my blue tomato. [Caitlin:] Well, cheer up.

We'll take this opportunity to explain more about GMOs.

Imagine if Felicia had actually managed to genetically manipulate a blueberry gene to

make a blue tomato.

She would have created a GMO or

Genetically Modified Organism. [Felicia:] Fortunately,

you've learned a lot about DNA and the ways we can manipulate it.

So now, we're ready to discuss GMOs. [Caitlin:] Practically all the food we eat

has been manipulated in some way, but not all of it has been genetically modified.

That might seem a little confusing,

so let's talk a little more about the definition of a GMO.

GMO specifically refers to foods that have had changes introduced into their DNA

through genetic engineering.

Genetic manipulation is different from plant breeding.

Humans have used conventional breeding techniques like hybridization and

cross-breeding for thousands of years. [Felicia:] But how is making GMOs different?

Let me give you a couple of examples: bananas versus papayas.

As you've already learned, the bananas we enjoy today are mutants that look a lot

different from their wild counterparts.

The same is true for papayas.

Well -- news flash -- one of these fruits is a GMO and one is not.

Want to guess which is which? [Caitlin:] The answer?

Bananas, non-GMO. Papaya, GMO.

Bananas have been cultivated by humans for around 7000 years.

The ones we eat today descended from two types of wild bananas.

Just by chance, some bananas produced mutant offspring that lacked seeds.

Because varieties with big seeds are practically inedible,

humans propagated the seedless variety for consumption.

In other words, humans selectively bred the naturally-occurring mutant.

[Felicia:] Papayas are GMOs.

In the 1990s, the papaya ringspot virus was wreaking havoc and

destroying crops, especially in Hawaii.

How was the papaya industry saved?

You guessed it! Genetic engineering. [Caitlin:] A team of scientists introduced a gene

into the papaya that gave it the abiliity to battle the papaya ringspot virus.

And thus, genetically modified papaya was born.

[Felicia:] So, to quickly recap,

a GMO is an organism whose genome has been modified through genetic engineering.

It does not include domesticated plants or

animals that have been selectively bred through traditional techniques.

For some people, the term GMO may conjure up an image of a killer tomato with teeth.

However, in actuality, GMOs -- the corn, soybeans,

and sugar beets many of us eat every day.

As the human population on Earth grows,

we'll need creative agricultural solutions in order to survive.

So, what's all the fuss about GMOs?

How can be make informed decisions about

the food we eat? [Caitlin:] When it comes to genetically modified organisms,

there are a few issues that often come up.

Are GMOs safe to eat?

How do GMOs affect the environment?

GMOs are safe and pose no more risk than crops that have been conventionally bred.

Who says so?

Over 275 scientific organizations from around the world,

including the World Health Organization, the US Food and Drug Administration,

and Health Canada, just to name a few.

How do they know?

They arrived at this conclusion after reviewing literally thousands of studies

that assess the safety of GMO crops.

It's also important to know that there are a number

of agencies who monitor the safety of GMOs.

In the United States, GMOs must be approved by the FDA,

USDA, and the Animal and Plant Health Inspection Services.

In Europe,

it's the European Food Safety Authority. [Felicia:] What about the impact of

genetically modified crops on the environment?

That's a little more complicated.

Scientists are still working on an answer.

But let's have a look at the findings of the largest study

to examine the effects of GMOs on the environment.

This study looks specifically at genetically modified corn, and

includes data from farmers across the United States, gathered over

a period of 14 years. [Caitlin:] Corn can be genetically modified to

kill insects that have eaten its kernels.

Since the corn produces its own insecticide,

farmers don't need to use as much insecticide to protect their crops.

The study found that farmers who grew genetically modified corn that

was insect resistant used 11% less insecticides over a 14-year

period as compared to other corn famers. [Felicia:] Well, but

another way of genetically modifying corn is to make it resistant to a type of

herbicide that is commonly sprayed on crops.

When farmers use this type of herbicide, the weeds are killed,

but their crops are not damaged.

Farmers who grew genetically modified corn that was resistant to

herbicides used slightly less herbicide over the course of the study.

[Caitlin:] That sounds pretty good, right?

Less insecticide and less herbicide. But the statistics don't tell

the entire story. [Felicia:] The problem is that weeds are plants,

and they can develop mutations that allow them to also become resistant to

herbicides.

In this study,

weeds developed a higher level of resistance than originally anticipated.

More and more plants were becoming herbicide resistant.

I hate to quote Jurassic Park, but, "Life finds a way."

In the end, farmers may be forced to switch to different herbicides,

or use more herbicide in order to combat weeds.

In fact, in the last five years of the study,

corn farmers were using more herbicide than at the outset of the study.

So, let's revisit the initial question once again.

Are GMOs bad for the environment?

It's not a simple yes or no answer.

What is clear is that we need to monitor insecticide and herbicide use,

and ensure regulations are in place

and are being followed. [Caitlin:] So far, we've been discussing

the controversies surrounding genetically modified crops.

However, genetically modified organisms developed to address healthcare

issues are far less controversial.

GMOs used in healthcare are a resounding success and have saved many, many lives.

Take insulin, for example. Thousands of people who suffer from Type 1 or

Type 2 diabetes are dependent on insulin for their survival.

Insulin is a hormone that is secreted by your pancreas to help control blood sugar.

People who suffer from diabetes don't make sufficient amounts of this hormone.

That means that they need insulin from another source.

But where can you find insulin?

Well, until around 1980, people with insulin-dependent diabetes relied on

insulin produced by grinding up pancreases from pigs and cows.

That's right: pigs and cows. [Felicia:] Eww. However,

genetic engineering dramatically changed that.

In 1978, scientists engineered E. coli to produce insulin.

Just four short years later, the United States Food and Drug Administration

approved synthetic insulin for human use. And the rest is history.

Today, the vast majority of insulin used worldwide is synthetic.

Pretty cool, right?

GMOs aren't just for crops.

[MUSIC]

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