Select your language

Suggested languages for you:
Log In Start studying!
StudySmarter - The all-in-one study app.
4.8 • +11k Ratings
More than 3 Million Downloads
Free
|
|

All-in-one learning app

  • Flashcards
  • NotesNotes
  • ExplanationsExplanations
  • Study Planner
  • Textbook solutions
Start studying

Gene Therapy

Save Save
Print Print
Edit Edit
Sign up to use all features for free. Sign up now
Biology

Because certain mutations can change gene function and cause disease, geneticists have been working hard to use healthy, cloned genes to compensate for faults in mutant genes.

The introduction of cloned genes into somatic cells or the alteration of existing genes to cure illness is referred to as gene therapy, and it has the potential to treat a wide range of ailments.

Genetic disorders

Over 7,000 genetic disorders have been identified in humans that involve abnormalities in a single gene. Examples include cystic fibrosis, sickle cell anaemia, and haemophilia. These conditions can be very good candidates for gene therapy.

Furthermore, many research efforts in gene therapy have been invested into treating conditions such as cancer and cardiovascular diseases that may occur at later stages of life. There is also a significant amount of research with regards to utilising gene therapy for combating infectious diseases such as AIDS.

AIDS = Acquired immunodeficiency syndrome.

There are five main steps involved in a gene therapy plan:

  1. Making a functional gene.
  2. Constructing a therapeutic vector that contains the functional gene.
  3. Conducting clinical trials to determine the safety and efficacy of the novel therapy.
  4. Determining the eligibility status of the patient.
  5. Delivering the functioning gene.
  6. Keep an eye on the long-term safety and efficacy of the treatment.

Types of gene therapy

Since all cells in the human body possess genetic material, they can all be potential candidates for gene therapy. Cells can be broadly classified into two categories of somatic and germline cells.

A somatic cell is any biological cell apart from a gamete, germ cell, gametocyte, or undifferentiated stem cell that forms the body of a multicellular organism.

A germline is a group of cells in a sexually reproducing multicellular organism that pass on their genetic material to their progeny. These cells undergo meiosis to produce gametes.

This type of classification also provides categorisation for gene therapy. Somatic gene therapy refers to interventions targeting somatic cells. Meanwhile, germline gene therapy targets reproductive cells or embryos before implantation.

It is possible to carry out gene therapy in humans exclusively in somatic cells since germline gene therapy raises ethical implications, and many countries have banned it.

To learn more about the ethical questions that gene therapy poses, read Ethical Considerations of Gene Therapy.

Despite the ethical and moral arguments, a Chinese scientist claimed in 2018 to have performed germline editing on two human embryos that had already been implanted and born1. The scientific community was astonished by this bold and, some would say, questionable move!

Strategies of gene therapy

There are a few gene therapy techniques that scientists use. These include gene augmentation, gene inhibition, and suicide gene therapy.

Gene augmentation therapy

For genetic recessive illnesses caused by a dysfunctional gene, a single normal copy of the gene may be enough to prevent or reverse the disease phenotype. Hence, the only thing needed to transfer would be a functional gene to replace the mutated dysfunctional one.

This method is called gene augmentation therapy, and it is best for treating disorders caused by a loss-of-function mutation in a gene that has resulted in a faulty or absent protein. This type of gene therapy could effectively treat conditions such as severe combined immunodeficiency and cystic fibrosis.

Nevertheless, from a practical standpoint, the success of gene augmentation therapy is contingent on at least two factors:

  1. The amounts of the functional protein generated by the augmented gene must be adequate.
  2. The disease's effects and consequences must still be reversible.

Gene inhibition therapy

For many disorders, restoring normal protein function is not sufficient to reverse the disease phenotype. They require the mutant gene's expression to be repressed.

Gene inhibition therapy (also known as gene silencing therapy) may be appropriate for dominant genetic disorders, some forms of infectious diseases, or certain forms of cancer.

For dominant genetic disorders, the logical setup of this technique would be to introduce a gene that can block the mutant gene's expression or interfere with the mutant protein's action.

With the discovery of the RNAi pathway by Andrew Fire and Craig Mello in 1998, this strategy became highly viable2. RNA interference (RNAi) is an endogenous biological process that regulates gene expression in the cells via short RNA sequences that are complementary to mRNA. RNAi is a form of post-transcriptional modification. You can learn more about it in our "Transcriptional Regulation" article.

The RNAi pathway provided an option to employ endogenous cellular machinery to modulate the expression of defective genes. Inserting a gene that encodes for small interfering RNAs – short single-stranded RNA molecules complementary to the mRNA of the defective gene – can lead to degradation of the mutant gene's mRNA via RNAi and prevent it from being translated. By inhibiting the expression of the mutant gene, the cell would be able to function normally.

The development of gene-editing tools such as CRISPR has provided further options for gene therapy. Gene editing techniques can be used to alter the genome by eliminating the faulty gene or accurately repairing it.

Suicide gene therapy

The two techniques mentioned above aim to restore cellular physiology and function and reverse the pathological phenotype. However, in certain types of conditions such as cancer, we are more interested in eliminating the defective cell rather than reversing it back to physiological states.

Suicide gene therapy can be used in this context, by using a transgene that works in one of two ways:

  1. The inserted transgene codes for a highly toxic protein that kills the defective cell. This transgene is called a 'suicide' gene.
  2. The inserted transgene encodes a protein that designates the defective cell as a target that the body's immune system can attack.

A transgene is a gene that has been artificially inserted into the genome of another organism.

Gene delivery systems

Transferring foreign genetic material into a cell or tissue is not easy because organisms have developed numerous defensive mechanisms to avoid it. Consequently, one of the most important concerns to address in a gene therapy plan is finding out which delivery method is most suited to maximise the treatment's effectiveness. There are currently two major types of delivery systems used for gene therapy: viral and non-viral systems.

The viral systems use modified viruses and their intrinsic capacity to infect cells with their genetic material. The big advantage of viral systems is their remarkable efficiency compared to other systems. Meanwhile, their main disadvantage is the safety problems associated with employing modified viruses.

Non-viral systems, on the other hand, incorporate a variety of chemical or physical approaches that have the benefit of being safe but the main disadvantage of being somewhat inefficient.

The optimum delivery mechanism for a specific gene therapy strategy is determined by a number of factors, including the size of the gene, the predicted outcome, and the side effect profile.

Ethical concerns about gene therapy

Gene therapy is prone to causing major ethical concerns, controversies, and disputes. Despite the numerous concerns, gene therapy has immense therapeutic potential and benefits. Like any other medical intervention involving human subjects, gene therapy must meet important requirements and considerations, such as ensuring informed consent and having a promising risk-benefit balance.

Nevertheless, the possibility of altering one's personal genetic information in germline cells raises the question of whether it should be allowed or not. The reason for this is the difficulty in drawing a line between gene enhancement and gene therapy since people may abuse this technology to alter the characteristics of their children to their own taste.

Gene Therapy - Key takeaways

  • The introduction of cloned genes into somatic cells or altering existing genes to cure illness is referred to as gene therapy.
  • Somatic gene therapy refers to interventions targeting somatic cells.
  • Germline gene therapy targets reproductive cells in an organism's germline.
  • Gene therapy techniques include:
    • Gene augmentation therapy
    • Gene inhibition therapy
    • Suicide gene therapy
  • There are currently two major types of delivery systems used for gene therapy: viral and non-viral systems.
  • Gene therapy is prone to causing major ethical concerns, controversies, and disputes. Germline gene therapy is prohibited in Western countries.

1. D Cyranoski, CRISPR-baby scientist fails to satisfy critics, Nature, 2018

2. Fire A, Xu S, Montgomery MK, Kostas SA, Driver SE, Mello CC, Potent and specific genetic interference by double-stranded RNA, Nature, 1998

Gene Therapy

The introduction of cloned genes into somatic cells or the alteration of existing genes to cure illness is referred to as gene therapy. 

Gene therapy is prone to causing major ethical concerns, controversies, and disputes. Despite the numerous concerns around it, gene therapy undeniably has immense therapeutic potential and benefits. Thus, gene therapy, like any other medical intervention involving human subjects, must meet important requirements and considerations, such as ensuring informed consent and having a promising risk-benefit balance.

Over 7,000 genetic disorders have been identified in humans that are known to involve abnormalities in a single gene. Examples of them include cystic fibrosis, sickle cell anaemia, and haemophilia. These conditions can be very good candidates for gene therapy. 

  1. Making a functional gene
  2. Constructing a therapeutic vector.
  3. Determining the eligibility status of the patient.
  4. Delivering the functioning gene
  5. Keep an eye on the long term safety and efficacy of the treatment

the possibility of altering one's personal genetic information in germline cells raises the question of whether it should be allowed or not. The reason for this is the difficulty in drawing a line between gene enhancement and gene therapy since people may abuse this technology to alter the characteristics of their children in order to their own taste. As a result, germline gene therapy is prohibited in Western countries. 

Final Gene Therapy Quiz

Question

What is gene therapy?

Show answer

Answer

The introduction of cloned genes into somatic cells or the alteration of existing genes to cure illness is referred to as gene therapy. 

Show question

Question

What are the five steps in a gene therapy plan?

Show answer

Answer

  1. Making a functional gene
  2. Constructing a therapeutic vector.
  3. Determining the eligibility status of the patient.
  4. Delivering the functioning gene
  5. Keep an eye on the long term safety and efficacy of the treatment

Show question

Question

How can the cells in multicellular organisms be broadly classified?

Show answer

Answer

Cells can be broadly classified into two categories of somatic and germline cells.  

Show question

Question

Define somatic cells

Show answer

Answer

A somatic cell, also known as a vegetal cell, is any biological cell apart from a gamete, germ cell, gametocyte, or undifferentiated stem cell that forms the body of a multicellular organism.

Show question

Question

Define germline

Show answer

Answer

A germline is a group of cells in a sexually reproducing multicellular organism that pass on their genetic material to their progeny. These cells undergo meiosis to produce gametes.

Show question

Question

What are the two gene therapy categories?

Show answer

Answer

Somatic and germline gene therapy

Show question

Question

What are the three main techniques of gene therapy?

Show answer

Answer

Gene augmentation, gene inhibition, and suicide gene therapy.  

Show question

Question

What conditions could gene augmentation therapy be used for?

Show answer

Answer

Gene augmentation therapy could be effective for treating conditions caused by a loss-of-function mutation in a gene that has resulted in a faulty or absent protein such as severe combined immunodeficiency and cystic fibrosis.  

Show question

Question

From a practical standpoint, what determines the success of gene augmentation therapy?

Show answer

Answer

  1. The amounts of the functional protein generated by the augmented gene must be adequate.
  2. The disease's effects consequences must still be reversible.

Show question

Question

What conditions is gene inhibition therapy effective for?

Show answer

Answer

Gene inhibition therapy (also known as gene silencing therapy) may be appropriate for dominant genetic disorders, some forms of infectious diseases, or certain forms of cancer. 

Show question

Question

What are the two main tools that can be used in a gene inhibition therapy plan?

Show answer

Answer

RNA interference and gene-editing tools such as CRISPR

Show question

Question

What are the two types of transgenes used in suicide gene therapy?

Show answer

Answer

1. The inserted transgene codes for a highly toxic protein that kills the defective cell. This transgene is called a 'suicide' gene. 

2. The inserted transgene encodes a protein that designates the defective cell as a target that can be attacked by the body's immune system.

Show question

Question

What is a transgene?

Show answer

Answer

A transgene is a gene that has been artificially inserted into the genome of another organism.

Show question

Question

What are the two main types of delivery systems used in gene therapy?

Show answer

Answer

viral and non-viral systems 

Show question

Question

What are the advantages and disadvantages of viral delivery systems?

Show answer

Answer

The major advantage of viral systems is their remarkable efficiency compared to other systems. Meanwhile, their main disadvantage is the safety problems associated with employing modified viruses.  

Show question

Question

What are the advantages and disadvantages of non-viral delivery systems?


Show answer

Answer

Non-viral systems have the major benefit of being safe, but the main disadvantage of being somewhat inefficient. 

Show question

Question

What are the core ethical principles of biomedical ethics?

Show answer

Answer

respect for patient's autonomy, beneficence, non-maleficence, and justice 

Show question

Question

What questions need to be asked when assessing the suitability of candidates for gene therapy?

Show answer

Answer

  1. Could the situation be improved by introducing one or two functioning genes?
  2. Do we know which genes are at work?
  3. Do we comprehend the disorder's biology?
  4. Can the gene be delivered to cells in the afflicted tissue?

Show question

Question

The impacts of gene editing can last more than one generation 


Show answer

Answer

True

Show question

Question

What factors does the risk-benefit analysis take into account?

Show answer

Answer

the patient's age, the severity of the disease, the availability of alternative treatment, the psychosocial, and economic costs of both performing and not performing the procedure, as well as yet unknown factors 

Show question

Question

A change in the genome of T cells aimed at rendering resistance to the HIV virus was discovered in 2016 to enhance vulnerability to the West Nile virus 


Show answer

Answer

True 

Show question

Question

What are the levels of beneficence in the medical context?

Show answer

Answer

  • Treatment for the patient; 
  • Treatment or prevention for other family members; 
  • relief or delaying of severe symptoms where no cure is available

Show question

Question

When can children and adolescents participate in gene therapy?

Show answer

Answer

when there is no safer treatment for their illness and the evidence supports a minimal risk of harm, children and adolescents can participate in and benefit from gene therapy trials. 

Show question

Question

When can people with diminished mental ability participate in gene therapy? 

Show answer

Answer

when there is no safer treatment for their illness and the evidence supports a minimal risk of harm 

Show question

Question

How can germline editing be helpful?

Show answer

Answer

Supporters of germline editing argue that deleting mutations in embryos inheriting a severe genetic condition will reduce the pool of mutations, which will benefit humanity in the long run.

Show question

Question

Define informed consent

Show answer

Answer

 If the information is supplied by a trained professional to a patient who is competent to understand and remember, make a decision, and communicate to the research or medical team, the patient's consent can be termed informed. 

Show question

Question

Genetic information can be difficult to understand for the general public or even some members of the healthcare team, which is why it should be presented by a geneticist, a genetic counsellor, or another person trained in genetics to ensure that the therapeutic intervention is correctly understood by the patient.

Show answer

Answer

True

Show question

Question

A patient with an untreatable serious disease who may perceive any therapy as preferable to his state may not always properly evaluate the risks 


Show answer

Answer

True

Show question

Question

What does the phrase "Designer babies" refer to?

Show answer

Answer

"Designer babies" is a commonly used phrase to describe human beings whose genes have been deliberately edited to offer heightened qualities and/or cosmetic qualities, such as the colour of their eyes, hair, or skin, based on their parents' preferences. 

Show question

Question

What is eugenics?

Show answer

Answer

Eugenics can be defined in several ways, but in general, it refers to the process of introducing specific modifications in a population's genetic composition in order to enhance its phenotype.

Show question

Question

There is a widespread agreement in the scientific community that germline editing, particularly nonmedical uses, should be prohibited, and that a major public consultation should take place before any such application is launched.


Show answer

Answer

True

Show question

More about Control of Gene Expression
60%

of the users don't pass the Gene Therapy quiz! Will you pass the quiz?

Start Quiz

Discover the right content for your subjects

No need to cheat if you have everything you need to succeed! Packed into one app!

Study Plan

Be perfectly prepared on time with an individual plan.

Quizzes

Test your knowledge with gamified quizzes.

Flashcards

Create and find flashcards in record time.

Notes

Create beautiful notes faster than ever before.

Study Sets

Have all your study materials in one place.

Documents

Upload unlimited documents and save them online.

Study Analytics

Identify your study strength and weaknesses.

Weekly Goals

Set individual study goals and earn points reaching them.

Smart Reminders

Stop procrastinating with our study reminders.

Rewards

Earn points, unlock badges and level up while studying.

Magic Marker

Create flashcards in notes completely automatically.

Smart Formatting

Create the most beautiful study materials using our templates.

Sign up to highlight and take notes. It’s 100% free.