Model Organisms

As you read this post remember that we love animals. We both dreamed of going to veterinary school one day, and we worked towards that goal until finding our love for research. With that love, we still accept that the use of model organisms is a critical component in advancing scientific research. It is not something scientists enjoy, and when we can use other methods we absolutely do. During this post, we’ll talk about the alternatives scientists use prior to animal research, the regulatory bodies overseeing live animal research and the model organisms most commonly used in the laboratory. 

We’re going to talk about cells again. (If you haven’t noticed, cells are a key component to learning more about science. So if you haven’t read our cells post, please do!) One of the major alternatives to using live animal models is the use of cells in petri dishes, something referred to as tissue culture. There are many immortal cell lines (meaning that they will grow forever without dying), but the most common is HEK293T cells, or Human Embryonic Kidney 293T cells (not to be confused with the T cells of the immune system). We can use these cells prior to using any animals to test our plan of action. This can help answer questions like: “does that new drug work in the way we want it to?” In this way, it helps prevent the unnecessary use of laboratory animals; however, it can not answer questions like: “what are the potential side effects of this drug?” For that, we need a model organism.

Universities that allow the use of animal models will have some form of an animal care program. This department will include an attending veterinarian who specializes in lab animal care, administrative bodies and an Institutional Animal Care and Use Committee (IACUC). There are a number of steps to go through before scientists can do any research on animals, including submitting a research proposal to IACUC. In this proposal, scientists must justify why animals are needed and list alternatives that would not work for answering their scientific question. One of the key components to animal research is called the 3 R’s: replace, reduce and refine. This means, replace animals with other scientific models whenever possible, reduce the number of animals needed and refine experimental techniques so they place minimal stress on the animals. If IACUC grants that researcher permission to use animals, they also hold the right to revoke that permission if there are any suspicions of the scientists deviating from what was written in the proposal without prior approval. Anyone at the university has the opportunity to report misconduct to IACUC anonymously. The animal care program and the rigorous process of gaining approval for animal use helps prevent those animals from being experimented on unnecessarily and helps ensure that they are receiving the best care possible.

So, now that we’ve explained all of the hoops scientists must jump through to use model organisms (and rightfully so), here is a list of some of the most common animals used in science, what makes them unique and the type of science they are used for. 


Zebrafish share ~60% of their DNA with humans, which makes them a great model organism for genetic studies. Zebrafish embryos are produced in large quantities (100-200 embryos per breeding pair) and are fertilized externally, allowing for easy collection of the embryos. These embryos are transparent, benefiting the developmental biology field, as scientists can observe the embryo as it grows from a single cell, to multicellular, to a larva. Further, at the single cell stage, zebrafish embryos are easily manipulated via single cell injections, allowing for genetic engineering and the ability to induce disease and/ or observe other changes.


Mice are probably the most commonly used animal in research. Mice and humans are very similar in many ways. Like humans, mice develop via egg and sperm, have the same main organs (heart, brain, lungs, kidney, etc.) and have similar digestive, reproductive and immune systems. Mice are used in cardiovascular, cancer and immunology research, just to name a few. There are multiple “strains” of mice intended for laboratory research. Each “strain” is a group of mice that are genetically identical. This prevents genetic differences from affecting experimental results. 


Rats are commonly used in neuroscience research to determine which neural pathways are affected in diseases. Rats have similar behaviors to humans, making them good models for diseases such as anxiety, post traumatic stress disorder, depression and addiction. By knowing how the brain is affected, researchers can begin to develop therapeutic interventions targeted towards these disorders.


Drosophila, better known as the fruit fly, serve as model organisms for many fields, including: genetics, signaling pathways, pain receptors and chronic pain, cancer and even behavioral things like alcoholism (don’t drink and “fly”). That’s right, those pesky little insects that swarm around your overly-ripe bananas are actually beneficial to research. Drosophila have a short life cycle, a relatively simple genome (DNA sequence) and compared to other animals, caring for drosophila in a laboratory setting is easier and less expensive.

Animal research has allowed for the development of chemotherapeutic drugs and immunotherapy (check out our cancer series), treatments for HIV and AIDS, and a better understanding of the biological mechanisms underlying diseases such as leukemia. We understand that this is not an easy topic to discuss, and we are open to hearing your thoughts on this and any other post. 

Thanks for reading and make sure to check back next week! In the meantime, let us know if you have any questions, comments or feedback and don’t forget to follow/ like us!

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Written by Annah & Megan
Illustrated by Rhea

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