10.4 Potential Advantages of Genetic Editing With Examples in Medicine and Agriculture

Introduction

Genetic editing (also called genome editing) is a group of techniques used by scientists to modify the DNA (genes) of an organism. It allows precise changes to be made in the genetic material, offering exciting possibilities in medicine and agriculture. This topic explains genetic editing, its techniques, and its potential advantages.

Definition

Genetic editing (also called genome editing) is a group of techniques used by genetic scientists to modify the DNA (genes) of an organism.

It is done by:

• Removing or adding nucleotides in genes
• Altering the nucleotide sequence at specific positions of the genome

Main Idea

Genetic editing can be performed in two ways:

• Ex-vivo/In-vitro Gene editing: Cells are removed from the body and grown in culture medium for applying any DNA editing technique.
• In-vivo Gene editing: This method is much complicated where cells/tissue is not removed from body. Gene editing enzymes or proteins are injected into the body for altering the DNA sequence of specific body tissue.

Major genetic editing techniques include:

• CRISPR-Cas9
• TALENs (Transcription Activator-Like Effector Nucleases)
• Zinc-Finger Nucleases (ZFNs)
• Base Editing

Core Concept

Major Genetic Editing Techniques

Potential Advantages of Genetic Editing

Detailed Explanation

1. What is Genetic Editing?

Genetic editing also called as genome editing. It is group of techniques used by genetic scientists to modify the DNA (genes) of an organism.

How it works:

- Genetic editing is done by removing or adding the nucleotides in genes or altering the nucleotide sequence at specific positions of the genome.

Simple explanation: Genetic editing is like using molecular scissors to cut and change specific parts of DNA.

Why this is important:

• It allows precise changes to be made in the genetic material.
• It has the potential to treat genetic diseases and improve crops.

2. Types of Genetic Editing

(a) Ex-vivo/In-vitro Gene editing:

- Cells are removed from the body and grown in culture medium for applying any DNA editing technique.

(b) In-vivo Gene editing:

• This method is much complicated where cells/tissue is not removed from body.
• Gene editing enzymes or proteins are injected into the body for altering the DNA sequence of specific body tissue.

Simple explanation:

• Ex-vivo — cells are taken out of the body, edited, and put back.
• In-vivo — cells are edited inside the body.

3. Major Genetic Editing Techniques

(1) CRISPR-Cas9

CRISPR-Cas9 is the most commonly and specifically useful tool for genetic editing. Genetic scientists use CRISPR-Cas9 to modify the DNA of living organism.

This technique consists of:

- A guide RNA and a Cas9 enzyme that cuts the DNA at the specific target site in DNA.

Science Titbits:

• CRISPR stands for "Clustered Regularly Interspaced Short Palindromic Repeats."
• CRISPR are repeated nucleotide sequences present in bacterial genome which are derived from the genome of viruses that have previously infected these bacteria.
• CRISPR act as memory which help the bacteria to defend against viruses.
• Cas9 stands for "CRISPR-associated protein 9." Cas9 protein is an enzyme that works as molecular scissors to cut the DNA strands.
• Guide RNA (gRNA) is a synthetic RNA sequence designed to match the target DNA sequence. gRNA directs the Cas9 enzyme to cut the DNA at specific target site.

Simple explanation: CRISPR-Cas9 is a tool that uses a guide RNA to find a specific DNA sequence and a Cas9 enzyme to cut it.

(2) TALENs (Transcription Activator-Like Effector Nucleases)

TALENs is somewhat similar to CRISPR. This technique uses:

• A unique protein to recognize specific sequence
• A nuclease enzyme to cut the DNA.

Simple explanation: TALENs uses proteins to find and cut specific DNA sequences.

(3) Zinc-Finger Nucleases (ZFNs)

ZFNs uses DNA cutting enzymes which are specifically designed for each gene to break the DNA at specific sites.

Simple explanation: ZFNs uses custom-designed enzymes to cut DNA at specific sites.

(4) Base Editing

This technique is a modified form of CRISPR in which highly specific single nucleotide is changed in the DNA without cutting the strands.

- One nucleotide base may be replaced to other e.g. A is replaced by G or C is replaced by T.

Simple explanation: Base editing changes a single DNA letter without cutting the DNA.

4. Potential Advantages of Genetic Editing in Medicine

(a) Managing Genetic Diseases

Genetic editing is used to modify the genetic mutations causing genetic diseases for example:

• Thalassemia
• Sickle cell anemia
• Cystic fibrosis
• Duchenne muscular dystrophy

Simple explanation: Genetic editing can correct the mutations that cause genetic diseases.

(b) Drug Development and Preclinical Testing

Genetic editing helps the biotechnologists to develop more accurate disease models for testing new drugs.

For example:

• Human genes are inserted into mice to develop humanized mice.
• Then different doses of newly developed drugs are applied on model animal.
• Response of drug on humanized animals precisely guide the researchers about effectiveness of newly developed drugs against specific human disease.
• To check the effect of new drug on organisms with specific genetic defect, gene knockouts cell lines are used in drug testing.

Simple explanation: Genetic editing helps create better animal models for testing new drugs.

(c) Cancer Therapy

Biotechnologists are using genetic editing to:

• Modify or knockout those genes which are involved in tumor growth and cancer progression.
• Alter genes responsible for resistance to chemotherapy.
• This approach is helpful in developing more effective drugs that specifically target cancer cells and do not effect healthy cells.

Simple explanation: Genetic editing can be used to target and destroy cancer cells.

(d) Viral Resistance

Genetic editing is being used to develop resistance against viral infections such as hepatitis and HIV.

• Genes producing host cell receptor proteins for viruses are modified to reduce the chances for viral infection and to improve the natural immune response.
• For example, editing of CCR5 gene in immune cells has been observed potentially effective to develop resistance to HIV infection rate.

Simple explanation: Genetic editing can make cells resistant to viral infections like HIV.

5. Potential Advantages of Genetic Editing in Agriculture

(a) Improvement in Food Crops

Genetic editing is being used to modify the genomes of important food crops at a specific nucleotide sequences to develop desired traits in the modified plant varieties.

Genetic editing is useful in developing:

• Disease resistance
• Pest resistance
• Drought tolerant plants
• Seeds and fruits enriched in nutrients and taste

For example:

- CRISPR-Cas9 technique has been used to edit genes in rice, maize and wheat to improve their yield and nutritional quality.

Simple explanation: Genetic editing can make crops resistant to pests, diseases, and drought, and improve their nutrition.

(b) Improvement in Dairy Livestock

Genetic editing may be used to modify existing genes or insert new genes for the development of beneficial traits especially in dairy livestock.

By this technique:

• Animals resistant to viral and bacterial diseases are produced.
• Modified genes may increase meat and milk production in cattle to solve the problem of food shortage.
• Gene editing is also used to develop better acclimatization ability in imported cattle breeds to local environmental conditions.

For example:

- Modification in the myostatin gene in buffaloes may develop extra muscle mass.

Simple explanation: Genetic editing can improve livestock by making them disease-resistant and increasing milk and meat production.

(c) Environment Friendly Farming

Large amount of pesticides are sprayed to protect the food crops and fruit plants.

Genetic editing may be helpful to:

• Reduce the need for pesticide use
• Promote naturally sustainable agriculture farming

For example:

• Editing of specific genes in food crops develop pest resistance in plants.
• This practice will gradually decrease the dependence on heavy use pesticide for healthy crops.
• This will reduce the environmental pollution and improve the food safety naturally.

Simple explanation: Genetic editing can reduce the need for pesticides, making farming more environment friendly.

6. Bioethical Limitations of Gene Editing

Although genetic editing is playing a significant role to address global challenges but it has also raised bioethical concerns.

Bioethical concerns related to gene editing include:

• Compromised safety
• Unequal chances for humanity
• Unimaginable consequences

Responsible and regularized use of genetic editing is highly important for more benefits and minimum risks.

Simple explanation: Genetic editing has ethical concerns that need to be addressed carefully.

Summary Table

Genetic Editing Techniques

Advantages in Medicine

Advantages in Agriculture

Intermediate Level

Genetic editing is a group of techniques used to modify the DNA of an organism.

Types:

• Ex-vivo/In-vitro: Cells removed, edited, and returned.
• In-vivo: Cells edited inside the body.

Techniques:

Advantages in medicine:

• Managing genetic diseases
• Drug development
• Cancer therapy
• Viral resistance

Advantages in agriculture:

• Improvement in food crops
• Improvement in dairy livestock
• Environment friendly farming

Bioethical limitations: Safety, unequal chances, unimaginable consequences.

Important Points

• - Genetic editing also called as genome editing. It is group of techniques used by genetic scientists to modify the DNA (genes) of an organism.
• - Genetic editing is done by removing or adding the nucleotides in genes or altering the nucleotide sequence at specific positions of the genome.
• - Gene editing can be performed in two ways:
• - Ex-vivo/In-vitro Gene editing: Cells are removed from the body and grown in culture medium for applying any DNA editing technique.
• - In-vivo Gene editing: This method is much complicated where cells/tissue is not removed from body. Gene editing enzymes or proteins are injected into the body for altering the DNA sequence of specific body tissue.
• - Major genetic editing techniques include:
• - CRISPR-Cas9: CRISPR-Cas9 is the most commonly and specifically useful tool for genetic editing. Genetic scientists use CRISPR-Cas9 to modify the DNA of living organism. This technique, consists of a guide RNA and a Cas9 enzyme that cuts the DNA at the specific target site in DNA.
• - TALENs (Transcription Activator-Like Effector Nucleases): TALENs is some similar to CRISPR. This technique use a unique protein to recognize specific sequence and a nuclease enzyme to cut the DNA.
• - Zinc-Finger Nucleases (ZFNs): ZFNs uses DNA cutting enzymes which are specifically designed for each gene to break the DNA at specific sites.
• - Base Editing: This technique is a modified form of CRISPR in which highly specific single nucleotide is changed in the DNA without cutting the strands. One nucleotide base may be replaced to other e.g. A is replaced by G or C is replaced by T.
• - Gene editing has multiple applications in genetic research especially related to medicine and agriculture.
• - Research involving genetic editing has significant potential for the treatment of genetic diseases, improving crop yield and quality.
• - Medicine:
• - Managing genetic diseases: Genetic editing is used to modify the genetic mutations causing genetic diseases for example; Thalassemia, Sickle cell anemia, Cystic fibrosis and Duchenne muscular dystrophy.
• - Drug Development and Preclinical Testing: Genetic editing help the biotechnologist to develop more accurate disease models for testing new drugs. For example, human genes are inserted into mice to develop humanized mice. Then different doses of newly developed drugs are applied on model animal. Response of drug on humanized animals precisely guide the researchers about effectiveness of newly developed drugs against specific human disease. To check the effect of new drug on organisms with specific genetic defect, gene knockouts cell lines are used in drug testing.
• - Cancer Therapy: Biotechnologists are using genetic editing to modify or knockout those genes which are involved in tumor growth and cancer progression. Genetic editing also being used to alter genes responsible for resistance to chemotherapy. This approach is helpful in developing more effective drugs that specifically target cancer cells and do not effect healthy cells.
• - Viral Resistance: Genetic editing is being used to develop resistance against viral infections such as hepatitis and HIV. Genes producing host cell receptor proteins for viruses are modified to reduce the chances for viral infection and to improve the natural immune response. For example, editing of CCR5 gene in immune cells has been observed potentially effective to develop resistance to HIV infection rate.
• - Agriculture:
• - Improvement in Food crops: Genetic editing is being used to modify the genomes of important food crops at a specific nucleotide sequences to develop desired traits in the modified plant varieties. Genetic editing useful in developing disease resistance, pest resistant and drought tolerant plants. This technique also useful in producing seeds and fruits enriched in nutrients and taste. For example, CRISPR-Cas9 technique has been used to edit genes in rice, maize and wheat to improve their yield and nutritional quality.
• - Improvement in Dairy livestock: Genetic editing may be used to modify existing genes or insert new genes for the development of beneficial traits especially in dairy livestock. By this technique animals resistant to viral and bacterial diseases are produced. Modified genes may increase meat and milk production in cattle to solve the problem of food shortage. Gene editing is also used to develop better acclimatization ability in imported cattle breeds to local environmental conditions. For example, modification in the myostatin gene in buffaloes may develop extra muscle mass.
• - Environment friendly farming: Large amount of pesticides are sprayed to protect the food crops and fruit plants. Genetic editing may be helpful to reduce the need for pesticide use and for naturally sustainable agriculture farming. For example, editing of specific genes in food crops develop pest resistance in plants. This practice will gradually decrease the dependence on heavy use pesticide for healthy crops, thus will reduce the environmental pollution and improve the food safety naturally.
• - Bioethical limitations of gene editing: Although genetic editing is playing a significant role to address global challenges but it has also raised bioethical concerns. Bioethical concerns related to gene editing include compromised safety, unequal chances for humanity and unimaginable consequences. Responsible and regularized use of genetic editing is highly important for more benefits and minimum risks.

Remember

• - Genetic editing = modification of DNA
• - Types = ex-vivo/in-vitro, in-vivo
• - Techniques = CRISPR-Cas9, TALENs, ZFNs, Base Editing
• - CRISPR-Cas9 = guide RNA + Cas9 enzyme
• - Medicine advantages = genetic diseases, drug development, cancer therapy, viral resistance
• - Agriculture advantages = food crops, dairy livestock, environment friendly farming
• - Genetic diseases = thalassemia, sickle cell anemia, cystic fibrosis, Duchenne muscular dystrophy
• - Viral resistance = CCR5 gene for HIV
• - Food crops = disease resistance, pest resistance, drought tolerance, nutrition
• - Dairy livestock = disease resistance, increased milk and meat, acclimatization
• - Bioethical limitations = safety, unequal chances, unimaginable consequences

Common Mistakes

• 1. Confusing genetic editing with genetic engineering.
• - Genetic editing = precise modification of DNA.
• - Genetic engineering = broader term including gene transfer.
• 2. Mixing up CRISPR-Cas9 and TALENs.
• - CRISPR-Cas9 = guide RNA + Cas9 enzyme.
• - TALENs = unique protein + nuclease enzyme.
• 3. Forgetting the difference between ex-vivo and in-vivo.
• - Ex-vivo = cells removed, edited, and returned.
• - In-vivo = cells edited inside the body.
• 4. Thinking genetic editing only has medical applications.
• - Genetic editing also has agricultural applications.
• 5. Believing genetic editing has no ethical concerns.
• - Genetic editing raises bioethical concerns.
• 6. Confusing gene knockdown and gene knockout.
• - Knockdown = temporary suppression.
• - Knockout = permanent inactivation.
• 7. Thinking base editing cuts DNA.
• - Base editing changes single nucleotides without cutting DNA.

Quick Revision

Genetic Editing Techniques

Advantages in Medicine

Advantages in Agriculture

60-Second Revision

• Genetic editing = modification of DNA
• Types = ex-vivo/in-vitro, in-vivo
• Techniques = CRISPR-Cas9 (guide RNA + Cas9), TALENs (protein + nuclease), ZFNs (designed enzymes), Base Editing (single nucleotide change)
• Medicine advantages = genetic diseases, drug development, cancer therapy, viral resistance
• Agriculture advantages = food crops, dairy livestock, environment friendly farming
• Genetic diseases = thalassemia, sickle cell anemia, cystic fibrosis, Duchenne muscular dystrophy
• Viral resistance = CCR5 gene for HIV
• Food crops = disease resistance, pest resistance, drought tolerance, nutrition
• Dairy livestock = disease resistance, increased milk and meat, acclimatization
• Bioethical limitations = safety, unequal chances, unimaginable consequences
• Warning: Do not confuse CRISPR-Cas9 (guide RNA + Cas9) with TALENs (protein + nuclease). Base editing changes single nucleotides without cutting DNA.