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Pharm Animals

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Les gènes et la condition humaine (entre comportement et biotechnologie)

Université du Maryland, College Park

4.6 (469 notes) | 37K étudiants inscrits

To acquire an understanding of the fundamental concepts of genomics and biotechnology, and their implications for human biology, evolution, medicine, social policy and individual life path choices in the 21st century.

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Compétences que vous apprendrez

Biology, Human Genetics, Genetics, Evolution

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4.6 (469 notes)

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GL

May 31, 2017

Really interesting material and well taught, even entertaining at times! :0) The quizzes were detailed but not excessively hard, and did a good job of assessing if you had learning the material.

SP

May 01, 2018

This course is great for someone who wants to learn the impact biotechnology has made in our lives and it's future prospects. The concepts covered in the course have been explained very well.

À partir de la leçon

An Introduction to Genetic Engineering and Learning the Lingo

Module Five introduces the world of genetic engineering concepts and biotechnology.

Transgenic Bacteria and Plants9:04

Pharm Animals10:04

Law and Genetics9:17

The Genetics of Cancer13:43

Treating Cancer10:06

Enseigné par

Raymond J. St. Leger
Professor
Tammatha O'Brien
Lecturer

Transcription

[MUSIC]

Hello and welcome back.

Today I'm going to continue talking about

biotechnology by talking about pharm animals.

That's pharm like pharmacy.

These are transgenic animals that have had

their genomes permanently altered through recombinant DNA technology.

These are animals, like transgenic sheep, that carry a gene to

synthesize a protein that can treat human diseases such as cystic fibrosis.

Creating transgenic animals is much more complicated

than creating transgenic bacteria or transgenic plants.

DNA must be inserted into the nucleus of an

egg or sperm, then carefully implanted into a surrogate mother.

If successful, these babies will be born with one copy

of the gene inserted into just one chromosome, so they're heterozygous.

To create an animal that has two copies of the gene, we need

to mate transgenic animals with each

other and identify which children are homozygous.

Once we create that animal line that's homozygous for the gene, we can mate

these animals with each other and the line will carry the gene that we inserted.

The most time consuming part of creating a transgenic animal, the

process of creating the initial line of animals that are homozygous.

Once this is done, it's a relatively inexpensive to continue the animal line.

A challenge faced when creating transgenic animals is inserting

the gene in the correct location.

The gene needs to be inserted next to or with a strong constitutive promoter.

You remember, that's a promoter that's always turned on, ensur-,

ensuring that the gene is transcribed and translated at high levels.

And, if you want the gene to be expressed in, say, the milk of sheep

or goat, you need to insert it next to a milk protein, such as casein.

So, the location of the gene insertion is critical for several reasons.

Remember, just like real estate, it's all about location, location, location.

The types of transgenic animals that can be

created are endless, but not without ethical implication.

Pigs, for instance, could be genetically modified for possible

human organ transplants, by inserting HLA, the human leukocyte angigen.

And when HLA is expressed in pigs, this will

allow their tissues to be compatible matches for humans.

But obviously there's a controversy over using animals, and specifically pigs.

As there could be cultural or religious issues, as well as ethical issues

at having to kill ascension animal to harvest tissue such as the heart.

But, by using animals to make human compatible organisms this would something

alleviate some, the sometimes fatal waiting game of long organ donor lists.

Another interesting aspect of DNA technology

is RNAi, also called RNA interference.

This is when a gene is inserted backwards

and makes a backwards copy of the transcript.

I'll explain how this affects gna-, gene transcription and translation.

The native RNA, that's the RNA that's normally

found in your body, that your body makes, will

bind with the backwards copy of the RNA that

we've created and produce a double stranded RNA complex.

This double stranded RNA complex will be cut off by your body.

That's because the cells of your body know that RNA should not be double stranded.

And it shouldn't be in your cells.

So, our cells have mechanisms to remove and destroy that double stranded RNA.

Scientists first observed the action of this RNAi,

when working with a flower called the petunia.

At the time they didn't fully understand what was happening.

They wanted to make a really purple flower, so they added

extra copies of the gene that coded for the purple pigment.

Well, in some plants, the extra purple pigment was inserted backwards.

And backwards copied the RNA transcript was made.

Instead of creating an

intensely super purple petunia, the researchers had flowers with

patches that were white, and lacked all purple pigment.

How could that be if they just inserted genes to make a lot of purple pigment?

The answer, as we now know, is RNAi.

When this double stranded RNA is encountered, not only do you destroy the

double stranded RNA, but our cells will go back and locate the original DNA

sequence that corresponded to the RNA and that sequence will be heavily methylated.

And do you remember what happens to DNA when it's heavily methylated?

The gene will no longer be expressed.

We can use what we know about RNAi to stop the expression of mutated

proteins that we see in certain cancers, or in the case of Huntington's disease.

That's due to a mutated Huntington protein that builds up in the brain.

You may have heard of gene therapy.

Gene therapy works to fix defective genes

by replacing them with properly functioning genes.

So, instead of removing gene function, like with

RNAI, we'll now discuss how to restore gene function.

One way to do that is by using transgenic viruses that contain a

properly functioning gene, along with a promotor

that'll be incorporated into a person's genome.

This introduced gene with its promotor will encounter,

enter the genome, replacing the function of a defective or missing gene.

Right now, gene therapy focuses on

treating diseases caused by single gene mutations.

Gene therapy's been approved for treating,

treatment of lipoprotein lipase deficiency, which affects

bod, the bodies ability to breakdown fatty acids and can cause severe pancreatitis.

With all of this DNA technology, ethical questions can be raised.

But most of us agree that using

this technology to treat diseases seems reasonable.

But, should genetically engineered human growth hormone be

used to stimulate growth in children who are deficient?

What would you consider deficient?

Should someone who's short, because both her

parents are short, be treated with growth hormone?

What about somebody who makes almost no growth hormone?

Where's that

threshold that warrants treatment?

So usually, short parents, we get short children.

But what if these parents just wanted a taller son?

And I say son, because parents are much less likely

to take a short daughter to get growth hormone therapy.

So should parents be allowed to use this medical

treatment to help a son develop a few inches taller?

The growth hormone shots can be painful, and

it teaches a child that they're not good enough

the way they are.

Is simply being short a condition that warrants medical intervention?

How do we decide what, when and who should be treated?

We can also use these technologies to diagnose disease.

In 2010, a young boy, Nicholas Volker, had a

serious intestinal issue that warranted many, many, many surgeries.

And the underlying cause of his intestinal condition wasn't known.

So, even though he underwent medical surgeries

to correct the symptoms, they didn't fix the

cause of his disease because doctors didn't

know what the cause of his disease was.

So they decided to do something extraordinary.

His doctors and researchers decide to sequence Nicholas' genome.

Researchers examined his genes, looking for the cause of this

rare disease to identify it, so they could hopefully treat it.

They found a mutation responsible for his intestinal

disease in a gene called X-linked inhibitor-of-apoptosis, XIAP.

He was deficient in it, so he had a point mutation.

Remember where we discussed point mutations in week one and,

with reference to the sickle cell trait?

In this case, it was just one substitution of

the 203rd amino acid of almost 500 amino acids.

And the amino acid, which was supposed to be

cytosine was pro-, was a completely different amino acid.

Tyrosine was present, which gave the protein a completely different shape.

And a different protein shape means the function of the protein was altered.

XIAP has two important jobs.

It blocks the process that makes cells die, which is called apoptosis

and it also helps prevent the immune system from attacking our intestines.

In the case of this young boy, the protein had an incorrect

sequence, so in his body the immune system was attacking his intestines.

This is called an autoimmune disease.

When the medical team diagnosed the correct gene defect, they gave

Nicholas a blood cord transplant using stem cells, that matched and

cured his gene defect.

The last interesting question for us to consider

in this talk has to deal with bio-technologies.

And should companies be allowed to own or patent genes?

Let's examine one gene, it's called delta 32 version CCR5.

It's inherited in a simple recessive fashion.

What that means is someone has to have two copies of delta 32

allele in order to have none of the CCR5 proteins present on their cells.

And people with two copies of this allele

are highly resistant to the common type of HIV.

They can be vulnerable to other strains.

But for the common HIV strain, it's very

difficult for the virus to enter the cells.

So, a patent of the gene, the CCR5 gene was given in 2000.

And obviously there was a lot of outrage in the scientific community.

Who should own the right to this gene sequence?

Should anyone own it?

Also back in 2000, a woman in England wanted

to become the first person to patent herself.

Donna McLean filed a patent for her

genomes stating that she was novel and useful.

In the United States there's been a lot of controversy over patenting genes.

BRCA, the breast cancer genes have been in

the news a lot, dealing with this patent law.

Patenting genes really limits the information available to researchers.

And because of this, the Supreme Court ruled in

2013, that naturally occurring genes may no longer be patented.

Not everyone was happy about this, as many private

industries kind of hoped to cash in on that patent.

[MUSIC]

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