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Somatic Gene Therapy is the process of cloning genes and injecting into affected cells to correct inherited diseases. Germ line is a process of making a change in an egg or sperm in someone, to be passed down into the offspring. MG

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Produced from 2001 through 2004, Iowa Public Television's Explore More online and broadcast series engages students in problems they can relate to, provides compelling content for investigation and gives students opportunities to form their own points of view on contemporary issues.
Although the full website has been retired, this archive provides links to project videos and related resources. Please contact us if you have questions or comments about Explore More.
The water we drink, the places we swim, and the plants and animals within our environments are increasingly threatened by pollution. Agriculture and urban runoff, industrial and household uses, and other sources impact this vital resource. What are the biggest threats to water quality in your area?

As our population grows, so do the demands we put on our natural areas. From houses to farms, landfills to hiking trails, working landscapes are a way of sustaining the land by balancing the social, economic, and ecological needs. Can we protect our natural areas and still use them?

From fossil fuels to biomass, there are several options in our current mix of energy resources. Investigate the advantages and drawbacks of each fuel. Discover the issues surrounding efficiency, consumption, infrastructure, and environmental consequences. How can we meet our energy needs in the future?

Genetic engineering has the potential to change the way we live. The science behind the agricultural, medical, and environmental achievements is spectacular, but this excitement is tempered by concern for the unknown effects of tampering with nature. How should we use genetic engineering?

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Produced from 2001 through 2004, Iowa Public Television's Explore More online and broadcast series engages students in problems they can relate to, provides compelling content for investigation and gives students opportunities to form their own points of view on contemporary issues.

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Gene Therapy reduces seriousness and pain from cancer and other diseases. MG

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Accomplishments | Alliance for Cancer Gene Therapy (ACGT) Foundation

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When ACGT was founded by Barbara and Edward Netter 13 years ago, no one could foresee that Cancer Immunotherapy would be selected as the "Breakthrough of the Year" in the December 2013 edition of Science Magazine,

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What does the future hold genetic engineering ?

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What does the future hold genetic engineering ?

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Scientist are looking into engineering genes to prevent cancer, and they're also looking at pre-birth vaccinations for other diseases.

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The answer to the question posed by the title of this article depends on which side of the fence you sit on. If you like what genetic engineering has to offer, the possibilities scientists are talking about at the moment will excite you. If you don't - it's probably going to give you the willies.

So, while we are going to explore the three major areas where genetic engineering could change things, there's a good chance they may not. Medicine, agriculture, and food production could all benefit. But, one suspects, it might be some time before they are allowed to, regardless of those benefits. Let's take a closer look.
Medicine
Make no mistake about it, genetic modification of human beings is controversial - but it will happen at some point. And, it shouldn't be too much of a surprise when it does - because it already has. There have been occasions when DNA has been altered in babies after they have been born, to treat acute diseases. And, of course, there have been plenty of examples of genetic alterations being used by athletes to enhance their performance.

In the future - and not too long from now - there could be many developments for both post birth and embryonic life. Scientists are already looking into engineering genes to prevent cancer and neurological disorders. They are also looking at pre-birth vaccinations for other diseases.

There is also the possibility of changing an embryo's DNA to improve intelligence, change appearance. There are even ideas for altering height and strength. Researchers can already do this with animals, and the sense is that if they could, they would already be doing so on humans.
Animals & Agriculture
There is a lot of controversy about genetically modified food, and, so far, most of that has been about crops. So, if people are feeling odd about eating an ear of GM corn, how do you think they are going to take to a GM pig, cow, or chicken? Well, the truth is they are already here.

Take chickens for example. Although the old rumor of KFC having to take the word chicken out of their name is nonsense, there is a grain of truth in it. These days, chickens have been selectively bred to lay more than 250 eggs a year. That's ten times more than their ancestors bothered to lay. And then there's the fact that chicken breasts are 80% larger today than they were in the 1950s. All through breeding - and, therefore, genetic modification.

And, in the future, things are likely to get stranger. Spider goats, for example, have spider DNA in them and produce a protein in their milk that can be extracted into durable silk thread. Check out these other strange tales of genetically altered animals. The problem for most people is, of course, that you shouldn't mess with nature. But, if genetically enhanced or modified animals help to feed the world, it's an argument that will lose steam at some point.

So, whatever happens, it's important to understand that we are already using GM products. And that we have been for years. But the next decade will throw up some exciting new developments, without a doubt.

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What Does The Future Hold For Genetic Engineering?

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The answer to the question posed by the title of this article depends on which side of the fence you sit on. If you like what genetic engineering has to offer, the possibilities scientists are talking about at the moment will excite you. If you don't - it's probably going to give you the willies.

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From prolonging life to creating new social barriers Crystal Lombaro covers it all in 10 abstract points.

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Gene therapy holds a lot of promise in the field of medicine. People every day are born with birth defects that affect their genetic makeup. This may create diseases that affect their quality of life, including shortening their expected life span. The pros and cons of gene therapy show that some of these issues could be treated or potentially cured in time, but the cost of doing so is often beyond what the average household can afford. Here are some additional key points to consider when looking at gene therapies as a viable medical treatment.

The Pros of Gene Therapy

1. It can prolong life.
Although gene therapy doesn't necessarily fix the issues that are present at a person's birth, it can treat those issues rather successfully. This allows an individual to live a rather normal life despite having a genetic condition that could make life difficult.

2. The scale of reach for gene therapy is quite large.
Antibiotics do not treat viral infections. Chemotherapy isn't something that is used to treat an outbreak of influenza. Many medical applications are only good for a limited treatment protocol, but not gene therapy. From Alzheimer's disease to Cystic Fibrosis, people young and old with any number of disorders could benefit from successful gene therapy research and treatment.

3. It could be tailored to replicate any protein.
What makes gene therapy such an exciting field of research is that it makes the production of protein that is dysfunctional become functional once again. Once the actual process of this is successfully developed, there is the potential that it could be replicated to any protein abnormality that may develop.

4. Gene therapy doesn't have to just apply to humans.
Gene therapies can also apply to animals, which could then help to stabilize the food chain and save producers money as therapies become less expensive. It could apply to plants as well, eliminating diseases that can devastate entire crops some seasons.

5. It could be used to enhance a person's overall health.
When certain genes are enhanced, the benefits they provide for overall health could enhance human life spans. Imagine being able to treat a future risk of cardiovascular disease not through the use of statins, but through gene therapies that "boost" a person's own biology. Increased muscle mass, better blood flow, and other benefits could change how we see ourselves in the future.

The Cons of Gene Therapy

1. It isn't a permanent solution - at the moment.
The ultimate goal of gene therapy is to create a treatment protocol that would allow someone to eventually be cured of their genetic abnormalities. Right now we're only able to take care of the symptoms of some diseases through gene therapy care. Eventually we'll need to deal with the root problem for this to be an effective medical treatment.

2. The process of gene therapy may have unintended side effects.
Because we're working with the building blocks that make people actually be "people," we really have no idea what current or future side effects may be when gene therapies are used. It could create mutations in future generations, create new diseases, or reduce instead of enhance a person's quality of life.

3. Gene therapy could create a new socioeconomic class divide.
In the US especially, medical care is often based on a person's ability to afford that care. Gene therapy is an expensive process, so it may not be readily available to all those who could benefit from it. Eventually, if left uncontrolled, the rich would get richer and the poor would just die.

4. Biology is very adaptable.
The discovery of antibiotics changed how medical care is administered. It also changed how bacteria behaves and has created resistant strains that are difficult to treat. This may also apply to gene therapy. Eventually human biology may adapt to these changes and be less responsive, creating more damage to the gene pool over the course of several generations.

5. Most observed benefits so far have been rather limited.
Although some benefits have been seen with current gene therapy techniques, they are often small benefits that are short-term in nature. Considering one treatment can cost upwards of $1 million, that a high price to pay for a small gain at best.

The pros and cons of gene therapy show that there is a lot of potential on the horizon for many who may be suffering from genetic disorders right now. With ongoing research, medical breakthroughs could be right around the corner and the hope that provides can be powerful medicine as well.

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Pros and Cons of Gene Therapy - Vision Launch

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Gene therapy holds a lot of promise in the field of medicine. People every day are born with birth defects that affect their genetic makeup. This may create diseases that affect their quality of life, including shortening their expected life span. The pros and cons of gene therapy show that some of these issues could ...

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This process is a mutation  between : enzymes connect with the DNA.
RNA T makes sure that the Cas9 enzyme cuts at the right point in the genome.

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CRISPR-Cas9 is a genome editing tool that is creating a buzz in the science world. It is faster, cheaper and more accurate than previous techniques of editing DNA and has a wide range of potential applications.

What is CRISPR-Cas9?

CRISPR-Cas9 is a unique technology that enables geneticists and medical researchers to edit parts of the genome by removing, adding or altering sections of the DNA sequence.

It is currently the simplest, most versatile and precise method of genetic manipulation and is therefore causing a buzz in the science world.

How does it work?

The CRISPR-Cas9 system consists of two key molecules that introduce a change (mutation) into the DNA. These are:

an enzyme called Cas9. This acts as a pair of 'molecular scissors' that can cut the two strands of DNA at a specific location in the genome so that bits of DNA can then be added or removed.

a piece of RNA called guide RNA (gRNA). This consists of a small piece of pre-designed RNA sequence (about 20 bases long) located within a longer RNA scaffold. The scaffold part binds to DNA and the pre-designed sequence 'guides' Cas9 to the right part of the genome. This makes sure that the Cas9 enzyme cuts at the right point in the genome.

The guide RNA is designed to find and bind to a specific sequence in the DNA. The guide RNA has RNA bases that are complementary to those of the target DNA sequence in the genome. This means that, at least in theory, the guide RNA will only bind to the target sequence and no other regions of the genome.

The Cas9 follows the guide RNA to the same location in the DNA sequence and makes a cut across both strands of the DNA.

At this stage the cell recognises that the DNA is damaged and tries to repair it.

Scientists can use the DNA repair machinery to introduce changes to one or more genes in the genome of a cell of interest.

Some bacteria have a similar, built-in, gene editing system to the CRISPR-Cas9 system that they use to respond to invading pathogens like viruses, much like an immune system.

Using CRISPR the bacteria snip out parts of the virus DNA and keep a bit of it behind to help them recognise and defend against the virus next time it attacks.

Scientists adapted this system so that it could be used in other cells from animals, including mice and humans.

What other techniques are there for altering genes?

Over the years scientists have learned about genetics and gene function by studying the effects of changes in DNA.

If you can create a change in a gene, either in a cell line or a whole organism, it is possible to then study the effect of that change to understand what the function of that gene is.

For a long time geneticists used chemicals or radiation to cause mutations. However, they had no way of controlling where in the genome the mutation would occur.

For several years scientists have been using 'gene targeting' to introduce changes in specific places in the genome, by removing or adding either whole genes or single bases.

Traditional gene targeting has been very valuable for studying genes and genetics, however it takes a long time to create a mutation and is fairly expensive.

Several 'gene editing' technologies have recently been developed to improve gene targeting methods, including CRISPR-Cas systems, transcription activator-like effector nucleases (TALENs) and zinc-finger nucleases (ZFNs).

The CRISPR-Cas9 system currently stands out as the fastest, cheapest and most reliable system for 'editing' genes.

What are the applications and implications?

CRISPR-Cas9 has a lot of potential as a tool for treating a range of medical conditions that have a genetic component, including cancer, hepatitis B or even high cholesterol.

Many of the proposed applications involve editing the genomes of somatic (non-reproductive) cells but there has been a lot of interest in and debate about the potential to edit germline (reproductive) cells.

Because any changes made in germline cells will be passed on from generation to generation it has important ethical implications.

Carrying out gene editing in germline cells is currently illegal in the UK and most other countries.

By contrast, the use of CRISPR-Cas9 and other gene editing technologies in somatic cells is uncontroversial. Indeed they have already been used to treat human disease on a small number of exceptional and/or life-threatening cases.

What's the future of CRISPR-Cas9?

It is likely to be many years before CRISPR-Cas9 is used routinely in humans.

Much research is still focusing on its use in animal models or isolated human cells, with the aim to eventually use the technology to routinely treat diseases in humans.

There is a lot of work focusing on eliminating 'off-target' effects, where the CRISPR-Cas9 system cuts at a different gene to the one that was intended to be edited.

Better targeting of CRISPR-Cas9

In most cases the guide RNA consists of a specific sequence of 20 bases. These are complementary to the target sequence in the gene to be edited. However, not all 20 bases need to match for the guide RNA to be able to bind.

The problem with this is that a sequence with, for example, 19 of the 20 complementary bases may exist somewhere completely different in the genome. This means there is potential for the guide RNA to bind there instead of or as well as at the target sequence.

The Cas9 enzyme will then cut at the wrong site and end up introducing a mutation in the wrong location. While this mutation may not matter at all to the individual, it could affect a crucial gene or another important part of the genome.

Scientists are keen to find a way to ensure that the CRISPR-Cas9 binds and cuts accurately. Two ways this may be achieved are through:

the design of better, more specific guide RNAs using our knowledge of the DNA sequence of the genome and the 'off-target' behaviour of different versions of the Cas9-gRNA complex.

the use of a Cas9 enzyme that will only cut a single strand of the target DNA rather than the double strand. This means that two Cas9 enzymes and two guide RNAs have to be in the same place for the cut to be made. This reduces the probability of the cut being made in the wrong place.

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CRISPR-Cas9 is a genome editing tool that is creating a buzz in the science world. It is faster, cheaper and more accurate than previous techniques of editing DNA and has a wide range of potential applications. CRISPR-Cas9 is a unique technology that enables geneticists and medical researchers to edit parts of the genome by removing, adding or altering sections of the DNA sequence.

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A "normal" gene is inserted into the genome to replace an "abnormal," disease-causing gene.

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In most gene therapy studies, a "normal" gene is inserted into the genome to replace an "abnormal," disease-causing gene. In cancer, some cells become diseased because certain genes have been permanently turned off.

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Gene therapy- hopes for the future  L.M.

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Gene therapy- hopes for the future  L.M.

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If genetics problems can be corrected through gene manipulation, individuals suffering from a disease may enjoy longer lives.

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Gene therapy is an experimental method of fighting disease that involves correcting or replacing a person's mutated or malfunctioning genes. This promising research is now being used in clinical trials and may lead to improved health outcomes for patients with inherited bleeding and immune disorders as well as some forms of blood cancer and other diseases.

What Is Gene Therapy?

Genes carry the DNA information needed to make proteins that are the building blocks of the human body. Some of these genes can become damaged through mutation, which can lead to disease conditions. Gene therapy is a scientific technique that uses genes to prevent or treat disease in a number of different ways:

Replace a damaged gene with a healthy copy of the gene.

Inactivate a gene that is functioning incorrectly.

Introduce a new gene into the body that may be needed for normal function.

Finding the Keys to Alter Body Chemistry

Currently, gene therapy can be used for conditions in which a change in the genetic coding of somatic cells can alter the course of a disease. For example, to correct a disease in which a specific enzyme is missing, the addition of a necessary gene component for production of the enzyme would fix the underlying problem of the disease. In many cases, harmless viruses are employed to serve as packets to carry the new gene to where it is needed. When used this way, the viruses are called "vectors," and their own genes may be removed and replaced with the working human gene. Once the gene is correctly placed, it can be switched on to provide the working "instructions" for correct function.

Conditions Being Treated with Gene Therapy

Although much of this may still sound like the realm of mad scientists tinkering with the human body, gene therapy is an accepted experimental technique that is currently being used to help patients with certain types of cancer to "target" specific antibodies that can be used to fight the disease. Gene therapy is also being used to correct deficiencies in the production of dopamine, such as in Parkinson's disease, correct some immune system problems, and restore components needed for normal blood cell function in those with certain blood diseases, such hemophilia and beta-Thalassemia. Gene therapy holds promise for treating a wide range of diseases, including cancer, cystic fibrosis, heart disease, diabetes, hemophilia and AIDS.

Potential Risks

Gene therapy does come with some potential risks, all of which, researchers are hoping to overcome. Because the genes have to be delivered using a carrier or "vector", the body's immune system may see the newly introduced viruses as intruders and attack them. It's also possible that the altered viruses may infect additional cells, not just the targeted cells containing mutated genes. There may also be some concern that the viruses may recover their original ability to cause disease, or that the new genes get inserted in the wrong spot in a patients DNA, leading to tumor formation.

Hope for the Future

Gene therapy holds promise as an effective treatment option for a variety of diseases at some point in the near future. An estimated 4,000 medical conditions are a result of gene disorders. If some of these genetic problems can be corrected through gene replacement or manipulation, individuals suffering from these diseases may enjoy longer, healthier lives, free of symptoms and the associated medical expenses.

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Gene Therapy - The Future of Medicine? | Science Care

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Gene therapy is an experimental method of fighting disease that involves correcting or replacing a person's mutated or malfunctioning genes. This promising research is now being used in clinical trials and may lead to improved health outcomes for patients with inherited bleeding and immune disorders as well as some forms of blood cancer and other diseases.

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Issues and Impacts of Gene Therapy  L.R.

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Issues and Impacts of Gene Therapy  L.R.

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This article covers the Ethics, social, economic, legal, and political impacts related to gene therapy.

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According to Merriam Webster Dictionary, eugenics is the "science that deals with the improvement... of hereditary qualities of a race or breed". The basic idea of eugenics revolves around specified and controlled human mating, but gene therapy itself could be used instead. Imagine if gene therapy is used to "cure" short height, ugliness, sexuality, and other "unwanted traits". If these "cures" could be made utilizing gene therapy, is it truly ethical to continue developing this technology?

Does the parents have the right to make the decision on what "traits" a child would have? If so, can it be ethical if the traits are cosmetic in nature? ​ Humanity is certainly not equal, despite what we believe. There are going to be people who are better and worser then the thing we do. If gene therapy can create total equality, is it a miracle, or a curse? ​

Some people have pointed out that gene therapy is akin to "playing god", since it is changing the code of life.

Another concern is based on genetic diversity. Could gene therapy limits the size of humanity's extremely diverse gene pool?

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According to Merriam Webster Dictionary, eugenics is the "science that deals with the improvement... of hereditary qualities of a race or breed". The basic idea of eugenics revolves around specified and controlled human mating, but gene therapy itself could be used instead. Imagine if gene therapy is used to "cure" short height, ugliness, sexuality, and other "unwanted traits".

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CRISPR is a unique way to to change, add or edit your genome  by segments with short repetitions of base sequences that just the geneticist do.

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CRISPR-Cas9 is a genome editing tool that is creating a buzz in the science world. It is faster, cheaper and more accurate than previous techniques of editing DNA and has a wide range of potential applications.

What is CRISPR-Cas9?

CRISPR-Cas9 is a unique technology that enables geneticists and medical researchers to edit parts of the genome by removing, adding or altering sections of the DNA sequence.

It is currently the simplest, most versatile and precise method of genetic manipulation and is therefore causing a buzz in the science world.

How does it work?

The CRISPR-Cas9 system consists of two key molecules that introduce a change (mutation) into the DNA. These are:

an enzyme called Cas9. This acts as a pair of 'molecular scissors' that can cut the two strands of DNA at a specific location in the genome so that bits of DNA can then be added or removed.

a piece of RNA called guide RNA (gRNA). This consists of a small piece of pre-designed RNA sequence (about 20 bases long) located within a longer RNA scaffold. The scaffold part binds to DNA and the pre-designed sequence 'guides' Cas9 to the right part of the genome. This makes sure that the Cas9 enzyme cuts at the right point in the genome.

The guide RNA is designed to find and bind to a specific sequence in the DNA. The guide RNA has RNA bases that are complementary to those of the target DNA sequence in the genome. This means that, at least in theory, the guide RNA will only bind to the target sequence and no other regions of the genome.

The Cas9 follows the guide RNA to the same location in the DNA sequence and makes a cut across both strands of the DNA.

At this stage the cell recognises that the DNA is damaged and tries to repair it.

Scientists can use the DNA repair machinery to introduce changes to one or more genes in the genome of a cell of interest.

Some bacteria have a similar, built-in, gene editing system to the CRISPR-Cas9 system that they use to respond to invading pathogens like viruses, much like an immune system.

Using CRISPR the bacteria snip out parts of the virus DNA and keep a bit of it behind to help them recognise and defend against the virus next time it attacks.

Scientists adapted this system so that it could be used in other cells from animals, including mice and humans.

What other techniques are there for altering genes?

Over the years scientists have learned about genetics and gene function by studying the effects of changes in DNA.

If you can create a change in a gene, either in a cell line or a whole organism, it is possible to then study the effect of that change to understand what the function of that gene is.

For a long time geneticists used chemicals or radiation to cause mutations. However, they had no way of controlling where in the genome the mutation would occur.

For several years scientists have been using 'gene targeting' to introduce changes in specific places in the genome, by removing or adding either whole genes or single bases.

Traditional gene targeting has been very valuable for studying genes and genetics, however it takes a long time to create a mutation and is fairly expensive.

Several 'gene editing' technologies have recently been developed to improve gene targeting methods, including CRISPR-Cas systems, transcription activator-like effector nucleases (TALENs) and zinc-finger nucleases (ZFNs).

The CRISPR-Cas9 system currently stands out as the fastest, cheapest and most reliable system for 'editing' genes.

What are the applications and implications?

CRISPR-Cas9 has a lot of potential as a tool for treating a range of medical conditions that have a genetic component, including cancer, hepatitis B or even high cholesterol.

Many of the proposed applications involve editing the genomes of somatic (non-reproductive) cells but there has been a lot of interest in and debate about the potential to edit germline (reproductive) cells.

Because any changes made in germline cells will be passed on from generation to generation it has important ethical implications.

Carrying out gene editing in germline cells is currently illegal in the UK and most other countries.

By contrast, the use of CRISPR-Cas9 and other gene editing technologies in somatic cells is uncontroversial. Indeed they have already been used to treat human disease on a small number of exceptional and/or life-threatening cases.

What's the future of CRISPR-Cas9?

It is likely to be many years before CRISPR-Cas9 is used routinely in humans.

Much research is still focusing on its use in animal models or isolated human cells, with the aim to eventually use the technology to routinely treat diseases in humans.

There is a lot of work focusing on eliminating 'off-target' effects, where the CRISPR-Cas9 system cuts at a different gene to the one that was intended to be edited.

Better targeting of CRISPR-Cas9

In most cases the guide RNA consists of a specific sequence of 20 bases. These are complementary to the target sequence in the gene to be edited. However, not all 20 bases need to match for the guide RNA to be able to bind.

The problem with this is that a sequence with, for example, 19 of the 20 complementary bases may exist somewhere completely different in the genome. This means there is potential for the guide RNA to bind there instead of or as well as at the target sequence.

The Cas9 enzyme will then cut at the wrong site and end up introducing a mutation in the wrong location. While this mutation may not matter at all to the individual, it could affect a crucial gene or another important part of the genome.

Scientists are keen to find a way to ensure that the CRISPR-Cas9 binds and cuts accurately. Two ways this may be achieved are through:

the design of better, more specific guide RNAs using our knowledge of the DNA sequence of the genome and the 'off-target' behaviour of different versions of the Cas9-gRNA complex.

the use of a Cas9 enzyme that will only cut a single strand of the target DNA rather than the double strand. This means that two Cas9 enzymes and two guide RNAs have to be in the same place for the cut to be made. This reduces the probability of the cut being made in the wrong place.

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CRISPR-Cas9 is a genome editing tool that is creating a buzz in the science world. It is faster, cheaper and more accurate than previous techniques of editing DNA and has a wide range of potential applications. CRISPR-Cas9 is a unique technology that enables geneticists and medical researchers to edit parts of the genome by removing, adding or altering sections of the DNA sequence.

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Gene therapy is when DNA is introduced into a patient to treat a genetic disease. The new DNA usually contains a functioning gene to correct the effects of a disease-causing mutation.

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Gene therapy is when DNA is introduced into a patient to treat a genetic disease. The new DNA usually contains a functioning gene to correct the effects of a disease-causing mutation.

Gene therapy uses sections of DNA (usually genes) to treat or prevent disease.

The DNA is carefully selected to correct the effect of a mutated gene that is causing disease.

The technique was first developed in 1972 but has, so far, had limited success in treating human diseases.

Gene therapy may be a promising treatment option for some genetic diseases, including muscular dystrophy and cystic fibrosis.

There are two different types of gene therapy depending on which types of cells are treated:

Somatic gene therapy: transfer of a section of DNA to any cell of the body that doesn't produce sperm or eggs. Effects of gene therapy will not be passed onto the patient's children.

Germline gene therapy: transfer of a section of DNA to cells that produce eggs or sperm. Effects of gene therapy will be passed onto the patient's children and subsequent generations.

Gene therapy techniques

There are several techniques for carrying out gene therapy. These include:
Gene augmentation therapy

This is used to treat diseases caused by a mutation that stops a gene from producing a functioning product, such as a protein.

This therapy adds DNA containing a functional version of the lost gene back into the cell.

The new gene produces a functioning product at sufficient levels to replace the protein that was originally missing.

This is only successful if the effects of the disease are reversible or have not resulted in lasting damage to the body.

For example, this can be used to treat loss of function disorders such as cystic fibrosis by introducing a functional copy of the gene to correct the disease (see illustration below).

Gene inhibition therapy

Suitable for the treatment of infectious diseases, cancer and inherited disease caused by inappropriate gene activity.

The aim is to introduce a gene whose product either:

inhibits the expression of another gene

interferes with the activity of the product of another gene.

The basis of this therapy is to eliminate the activity of a gene that encourages the growth of disease-related cells.

For example, cancer is sometimes the result of the over-activation of an oncogene (gene which stimulates cell growth). So, by eliminating the activity of that oncogene through gene inhibition therapy, it is possible to prevent further cell growth and stop the cancer in its tracks.

Killing of specific cells

Suitable for diseases such as cancer that can be treated by destroying certain groups of cells.

The aim is to insert DNA into a diseased cell that causes that cell to die.

This can be achieved in one of two ways:

the inserted DNA contains a "suicide" gene that produces a highly toxic product which kills the diseased cell

the inserted DNA causes expression of a protein that marks the cells so that the diseased cells are attacked by the body's natural immune system.

It is essential with this method that the inserted DNA is targeted appropriately to avoid the death of cells that are functioning normally.

How is DNA transfer done?

A section of DNA/gene containing instructions for making a useful protein is packaged within a vector, usually a virus, bacterium or plasmid.

The vector acts as a vehicle to carry the new DNA into the cells of a patient with a genetic disease.

Once inside the cells of the patient, the DNA/gene is expressed by the cell's normal machinery leading to production of the therapeutic protein and treatment of the patient's disease.

Challenges of gene therapy

Delivering the gene to the right place and switching it on:

it is crucial that the new gene reaches the right cell

delivering a gene into the wrong cell would be inefficient and could also cause health problems for the patient

even once the right cell has been targeted the gene has to be turned on

cells sometimes obstruct this process by shutting down genes that are showing unusual activity.

Avoiding the immune response:

The role of the immune system is to fight off intruders.

Sometimes new genes introduced by gene therapy are considered potentially-harmful intruders.

This can spark an immune response in the patient, that could be harmful to them.

Scientists therefore have the challenge of finding a way to deliver genes without the immune system 'noticing'.

This is usually by using vectors that are less likely to trigger an immune response.

Making sure the new gene doesn't disrupt the function of other genes:

Ideally, a new gene introduced by gene therapy will integrate itself into the genome of the patient and continue working for the rest of their lives.

There is a risk that the new gene will insert itself into the path of another gene, disrupting its activity.

This could have damaging effects, for example, if it interferes with an important gene involved in regulating cell division, it could result in cancer.

The cost of gene therapy:

Many genetic disorders that can be targeted with gene therapy are extremely rare.

Gene therapy therefore often requires an individual, case-by-case approach. This may be effective, but may also be very expensive.

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Gene therapy is when DNA is introduced into a patient to treat a genetic disease. The new DNA usually contains a functioning gene to correct the effects of a disease-causing mutation. Gene therapy uses sections of DNA (usually genes) to treat or prevent disease.