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Genetically modified animals are animals whose genetic materials have been artificially altered. This is often done to change certain characteristics in the animal. 

Genetic modification has been used in animals for a variety of purposes, such as creating disease-resistant livestock or producing transgenic mice for medical research. However, there are also concerns about the ethical implications of genetic modification and its potential impact on ecosystems if genetically modified animals were released into the wild.

how animals are genetically modified


There are a few different methods used to genetically modify animals, including:

  • Transgenesis:

This involves introducing foreign genetic material into the animal’s DNA to give it new traits. 

This can be done using a variety of techniques, such as microinjection (a tiny needle is used to inject genetic material directly into the nucleus of a cell), electroporation (an electrical field to create small holes in the cell membrane, which allows genetic material to enter the cell), and viral vectors (These are viruses that have been modified so that they carry specific genes that scientists want to introduce into an animal’s cells).

  • Gene Editing

This is a newer technique that allows scientists to make precise changes to an animal’s DNA using tools like CRISPR-Cas9. (Cas9 is an enzyme that acts like a pair of molecular scissors, cutting the DNA at specific locations. CRISPR refers to a series of genetic sequences that guide Cas9 to the right spot on the DNA). With gene editing, specific genes can be added, removed, or modified.

  • Cloning

Cloning involves creating an exact genetic copy of an existing animal by transferring its DNA into an egg cell and implanting it into a surrogate mother.


Humans have changed animal DNA for as long as we can remember. They began changing animal’s DNA through breeding strategies. (Research source: Havard University)

Breeding Strategies:


Crossbreeding involves mating two different breeds of animals to produce offspring with a mix of traits from each parent. The goal is to take advantage of the strengths of each breed while minimizing their weaknesses. It focuses on mixing breeds to create new combinations of traits.

For example, crossing a dairy cow with a beef bull can produce offspring that have good milk production and meat quality.

Selective Breeding

Selective breeding involves choosing individual animals with desirable traits and breeding them together to create offspring with those same traits. This process is repeated over multiple generations until the desired trait becomes fixed in the population. It focuses on amplifying specific traits within one breed.

For example, selecting chickens for high egg production or cows for fast growth rate.

genetic modification

Modern Genetic Modification:

  • The first time GMO technology was used to change a living thing was in 1973 by Herbert Boyer and Stanley Cohen. They were able to transfer genetic material from one organism to another. They used bacteria as their sample.
  • Other scientists, like Rudolf Jaenisch and Beatrice Mintz, also played a role in getting people to use GMOs. They made the first genetically modified animal by putting foreign genes into mice.
  • Unlike crossbreeding and selective breeding, GMO technology allows scientists to make specific changes to genes. This can be more effective than breeding techniques.


Here are some examples of the impact of genetically modifying animals:

what animals have been genetically modified


  • Scientists have created chickens that are more disease resistant, grow faster, and produce more eggs. 
  • These changes have reduced their environmental impact, because if it takes less chickens to produce the needed supply, they are creating less waste.


  • Salmon have been modified to grow faster than normal salmon do and to contain higher levels of omega-3 fatty acids, which makes them more nutritious for humans.


  • Mosquitoes are one of the most dangerous insects in the world because of the diseases they can spread, including malaria, dengue fever, and Zika virus. Scientists have changed the DNA of mosquitoes to stop the spread of these diseases. 
  • One company has made mosquitoes with genes that make them die off on their own. Before they are old enough to be adults, the offspring of modified mosquitoes die.

Mice and Rats

  • After scientists create mice or rats with genetic changes, they can observe how these animals behave and function. The changes in behavior and physical health of these animals can be similar to those seen in humans with neurological disorders. By studying these animals, researchers can learn more about how the diseases work and develop new ways to treat them.


  • Scientists can change the genes of pigs to make them similar to humans. This helps them study human diseases and test new drugs on pigs before trying them on people. 
  • Pigs can also be changed to produce human proteins or organs that might be used for transplants in humans one day.


  • Cows have been modified to make more milk. 
  • Another goal is for cows to make milk that is closer to human milk. Such milk would be easier for the human body to break down. 

genetically engineered livestock

Genetically Engineered Livestock:

  1. Pigs

  • Pigs are one of the older animals scientists use to study GMO technology. Scientists make GM pigs for the drug industry. 
  • The organs of GM pigs help grow new medical ideas.
  • The US Food and Drug Administration now allows the sale of GM pigs for people to eat. GM pigs produce more meat than natural pigs. 
  1. Cows

  • Genetic engineers from different parts of the world changed the DNA of cows. Genetically modified cows are different from cows that are naturally bred.
  • For example, Argentinian and Chinese scientists made cows have more milk.
  • Another goal is for cows to make milk that is closer to human milk.  This is easier for the human body to break down. 

Genetic engineers are constantly working to modify more animals. In fact, scientists think there are a lot of good things about genetically changing sheep, goats, horses, and goats. (Research source: The Guardian)



  • Scientists can create animals that are resistant to certain diseases and pests, which could improve animal health and reduce the need for harmful pesticides or antibiotics.
  • Animals can be modified to produce more food, which can increase food security.
  • Better quality products can be created, such as meat or milk with lower fat content.
  • Researchers can also use genetically modified animals to study human diseases and test new drugs before trying them on people, potentially leading to better treatments.


  • There is still a lot of uncertainty about the long-term effects of genetic modification on animals and the environment.
  • Genetic modification could lead to unintended consequences, such as creating new diseases or harming other species that interact with the genetically modified animals.
  • Some people have ethical concerns about the welfare of genetically modified animals and whether it is right to manipulate their genes for human gain.
  • Genetically modified animals that are released could become invasive species that overwhelm the natural species in the environment.


Changes to an organism’s genetic makeup has unexpected effects on the natural world. (Research source: Scitable by Nature Education)

GMOs Can Impact Biodiversity:

There are many ways genetic modification impacts the population of both plant and animal groups in an ecosystem.

Some problems with genetically modified animals include:

  • Animals with changed genetic material often overwhelm other animals in a habitat.
  • It’s possible for genetically modified animals to carry new diseases. These diseases could kill off other species of animals.
  • Also, GM animals may eat too much food in the environment.


Genetically modified animals may or may not reproduce:

  • Depending on the type of modifications some modified animals may not have the ability to reproduce.
  • Often scientists remove the DNA sequence that allows reproduction. However, sometimes the ability to reproduce is accidentally deleted! 


Scientists can use genetic engineering techniques to make animals that are better than animals that haven’t been genetically modified. When GMO technology is used, it can change the field of medicine by making animals that are better at fighting off diseases.

It can also boost the production of animals and crops, which means that global food security will be better. However, most GMOs are not safe for people to eat, so more research needs to be done to make them safe.

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