Genetic Manipulation

Genetic Manipulation: Examples

Since the 1980s, genetic manipulation has been used in a variety of industries, including medicine and agriculture.

Cancer Treatments

In 2013, a gene-editing tool called CRISPR was brought to life. It functions like a precise pair of scissors, slicing pieces of DNA. Its first clinical trial in cancer therapy took place in 2019, making genetic changes to T-cells (immune system cells that can kill cancer). The trial was deemed safe and did not trigger an immune reaction.

Medicine Production

Earlier we learned that the first GMO product approved was human insulin. Since then, genetic engineering has been used to mass-produce a variety of drugs, including:

• Human growth hormones

• Albumin (a chemical used in transport)

• Antihaemophilia drugs

• Infertility drugs

• Vaccines

Brewing Yeast

A team of scientists in California have created a genetically modified yeast that mimics the flavour and aroma of hops, without any interaction with the plant.

Agriculture

Genetic manipulation is common in agriculture. Most GM crops were developed to prevent yield loss and control weeds. The three most common reasons for genetically manipulating crops are:

1. Pest resistance
2. Tolerance of herbicides used to control weeds
3. Resistance to plant viruses

It's not just plants – genetic manipulation is used to transfer desirable traits between animals. However, only one GM animal has been commercialised; a fast-growing variety of salmon.

Manipulation of Genetic Material in Agriculture

What are the different techniques used to manipulate genetic material in agriculture?

Selective Breeding

Farmers have been using selective breeding for millennia to alter the traits of crops and livestock. How does it work?

1. Farmers select individuals with desirable characteristics and breed them together.

2. They choose the offspring with the best combinations of traits and breed them together.

3. This process continues over many generations until the trait has been established in the population.

Using selective breeding, farmers have converted wild plants and animals into the crops and livestock we use today. Desired characteristics include:

• Increased meat or milk production

• Larger fruit and eggs

• Increased nutritional content

• Disease resistance

• Calm temperament

Limitations of Selective Breeding

• A trait can only be bred into individuals if it already exists in a species. So, selective breeding is limited by existing genetic variation.
• Selective breeding is a slow process, especially in animals.
• Offspring are genetically similar, so are equally vulnerable to the same diseases. Inbreeding can also result in a loss of alleles, limiting genetic variation.

It's important to maintain genetic diversity in nature because new traits from wild plants can be bred into crops to help them respond to climate change.

Vegetative Propagation

Vegetative propagation is a form of asexual reproduction. It involves taking part of a parent plant, causing it to regenerate into a new plant. There are two methods: cutting and grafting.

• Cutting: a branch of the parent plant is cut off, its lower leaves removed, and the stem is planted in compost. Plant hormones are added to encourage root growth.

• Grafting: a cutting from a plant is attached to the stem of another plant.

Plants grown by vegetative propagation are genetically identical to each other, so useful characteristics will always be passed on. Vegetative propagation only requires one plant, and is a very fast method of genetic manipulation.

Figure 2 – Genetically identical cuttings being planted in a greenhouse. Unsplash

Limitations of Vegetative Propagation

• Artificially propagated plants have a lower lifespan than seed propagated plants.

• Like selective breeding, vegetative propagation is limited by existing genetic diversity.

• Vegetative propagation requires special training, and is more expensive than seed propagation.

• Genetically identical plants are equally vulnerable to the same diseases.

Genetic Engineering

Also known as genetic modification, genetic engineering involves modifying an organism's genome by introducing a gene from another organism. How does it work?

1. Scientists select the desired characteristic and identify the required gene.

2. Enzymes are used to isolate the gene and cut it out of the genome. The gene is inserted into a vector, usually a bacterial plasmid or the virus.

3. The vector inserts the gene into the required cell.

4. The genetically modified organism reproduces, either sexually or asexually. The offspring will develop with the desired characteristics.

Crops and livestock are genetically engineered to obtain useful characteristics such as improved nutritional content, resistance to pests and diseases, increased yield, and tolerance to climatic extremes.

Limitations of Genetic Engineering

• A trait that benefits one organism may harm another.
• Genetic engineering may lead to health concerns, such as allergic reactions or toxins.
• Genetic engineering research is incredibly expensive.
• Like selective breeding, it can take a long time to see results, especially when modifying an animal's genome.

Genetic Manipulation Ethics

Although GM crops and animals have excellent benefits, they bring a range of ethical concerns.

Moral Objections

Some believe that it's not ethical to interfere with nature. Altering the genome of living organisms in this way could be considered intrinsically wrong, or immoral.

There is a demand for transparent labelling guidelines, so consumers can make informed choices when purchasing GM foods.

Wellbeing Concerns

There are wellbeing concerns for GM animals, who cannot consent to genetic manipulation. Furthermore, selective breeding techniques regularly result in inbreeding. This increases the risk of inheriting harmful homozygous alleles, that may cause disease or suffering in the animal.

Financial Control

GM crops are more expensive than regular crops, so they can't be afforded by people in developing countries. In these countries, GM crops may aid the reduction of poverty and improve food security.

High prices are linked to GM crop patents. Farmers are not allowed to save GM seeds for the next season, but must instead buy new seed each year at a set price. Just 10 companies control 75% of global seed sales, dominating the global food system.

'Designer Babies' and Eugenics

If we can manipulate the genetics of animals, why couldn't we do the same to ourselves? We can – to a minor extent. Couples who are carriers for a genetic disease can undergo preimplantation genetic testing. Embryos fertilised via IVF are tested for a range of genetic disorders before being implanted into the woman.

Figure 3 – A technician using a genome sequencer. This high-tech piece of equipment can be used to analyse an embryo's DNA during preimplantation genetic testing. Unsplash

Although it helps prevent lifelong disease and disability, preimplantation genetic testing has raised ethical concerns. What if manipulating genetics went further? Experts have warned about the dystopian future of 'designer babies' and its link to human eugenics.

If parents can pick and choose traits of their future offspring, ranging from their eye colour to their personality and intelligence, what would happen to society?

Genetic Manipulation: Advantages and Disadvantages

This table summarises the advantages and disadvantages of genetic manipulation in agriculture.

I hope that this article has clarified genetic manipulation for you. Remember that it is the modification of an organism's genes using technology. In agriculture, there are three techniques of genetic manipulation: selective breeding, vegetative propagation, and genetic engineering.

^{1. Garden Organic, GMOs - political and ethical concerns, 2022}

^{2. National Cancer Institute, How CRISPR Is Changing Cancer Research and Treatment, 2020}