In Vivo vs. In Situ Experiments

Instructor: Jose Hernandez
This lesson will cover the differences between ''in vivo'' and ''in situ'' experiments. We will briefly cover the advantages and disadvantages of each type.


Have you ever wondered how scientists discover drugs before the medication is released to the public? Or how they have a better understanding of a disease? Or even perhaps how changes in our DNA can alter our body or cause disease?

Scientists address these questions by performing a wide range of experiments. These experiments can be categorized by the type of model, or organism, being used.

  • In vivo experiments are when a live organism is used. The term is Latin for 'within the living'.
  • In situ experiments in a lab context focus on a specific protein or gene, looking at it inside an entire organism. The term is Latin for 'on site' or 'in position'.

There are other types of categories that scientists use, such as ex vivo and in vitro to name a few, but we'll leave those for other lessons. Let's look at the advantages and disadvantages of just these two categories, and how scientists use these type of experiments to improve our quality of life.

In Vivo Experiments

For in vivo experiments, researchers can use a wide range of organisms depending on the type of study being done. Fruit flies can be used to study alcohol behavior or how different genes can affect the entire organism, given the ease of genetic manipulation for the species.

Zebrafish can be genetically modified to study how the different genes affect development. Other animals such as mice, rats, and apes are also commonly used in a laboratory depending on the type of research being performed.

Zebrafish are a common animal model used for in vivo experiments.


Performing in vivo experiments has its advantages. Although the experiments are performed on a wide range of animal models, the models used have similar features to humans that make them useful for research.

Animals such as zebrafish and sea urchins are externally fertilized, meaning that scientists can perform their studies upon fertilization of the embryo and study the organism as it develops to a mature animal.

Another advantage of performing experiments in vivo is fast development times. Scientists may choose an organism based on reproduction rate, therefore only having to wait days or weeks for a new generation.

However, one of the main advantages of performing experiments in vivo is to study the development of an organism while it is still alive and seeing how different mutations or defects affects an entire animal model.


There are however a few disadvantages to performing experiments in vivo. Although scientists try very hard to draw comparisons between the animal model and humans, sometimes only so many comparisons can be made.

Also, animal safety and well-being requires limitations on the type of experiments that are allowed. Animals are also costly to maintain.

When in vivo experiments are performed to test drugs, there are several disadvantages to animal models:

  • Doses might change between species, making it harder to find an optimal dose
  • Life expectancy varies - a short-lived organism may hide long-term effects
  • Differences in genes among species
  • Diet provided to the animals might affect results
  • Size of the organism might make results hard to interpret

In Situ Experiments

Although studying something in an organism might sound similar to in vivo experiments, in situ experiments are not performed on live organisms themselves. Scientists can use different techniques to look at a gene of interest without having to remove it from its natural environment.

This is performed by adding chemicals to preserve the tissue being studied, and then using different different dyes or fluorescence techniques to look at the gene of interest.


There are several advantages to using in situ experiments. As researchers perform several experiments simultaneously, these experiments can be postponed until the scientist has time.

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