Section 1: Using Mice in Research

The Mouse: A Model System
Raising Mice in the Laboratory
Mouse Cages

Section 2: Experimental Design

Making a Hypothesis
Designing the Right Experiment
Measuring Learning in Mice

Section 3: Data and Conclusions

Gathering Data
Analyzing Data
Interpreting Data
Drawing Conclusions

The Mouse: A Model System

Scientists use laboratory animals as model systems to study conditions that affect humans. A mouse is a good model system for a human because mice and humans both control their internal functions in the same way and respond similarly to infection and injuries.

Using mice for research is less expensive and time-consuming than using humans. Researchers can control experimental conditions more easily for animals than for humans.

Raising Mice in the Laboratory

Researchers follow strict guidelines for ethical treatment of animals. Mouse cages are checked daily to make sure mice have fresh food and water. Cages are kept clean and comfortable. The number of mice per cage is determined by the size of the mice and the size of the cage.

Mouse Cages

Mice are social animals that like to be housed together. The following are examples of different living conditions.

Making a Hypothesis

A hypothesis is a testable statement that predicts a result. For example:

Mice raised in different types of cages will learn a task at different rates.

Researchers can make a specific hypothesis if they know something about the situation they are testing. For example, if they know that climbing ladders affects learning, they might make this hypothesis:

Mice raised in cages with ladders learn more quickly than mice raised in cages without ladders.

Designing the Right Experiment

Researchers identify experimental and control groups based on their hypothesis. Consider the hypothesis:

Mice that exercise learn more quickly than mice that do not exercise.

The experimental group are mice that use an exercise wheel. The control group are mice that do not use an exercise wheel, because exercise wheels are not provided under standard laboratory conditions.

The experimental group are mice that use an exercise wheel. The control group are mice that do not use an exercise wheel, because exercise wheels are not provided under standard laboratory conditions.

All other conditions are the same for both groups.

Measuring Learning in Mice

Learning in mice can be measured using the Morris Water Maze test. In this test, mice are placed in a swim tank filled with water in which powdered milk has been dissolved. The cloudiness of the water prevents the mice from seeing a platform just under the surface of the water. A mouse standing on the platform can keep its head above water. Mice prefer standing on the platform to swimming in the tank. When mice are placed in the tank, they swim around until they find the platform. The mice use visual cues to orient themselves while they are inside the tank. The visual cues can be pictures or objects which are placed around the room.

Gathering Data

Data are the results of experiments. Scientists write down data as they conduct their experiment. They record their data in a lab notebook, which can be on paper or on the computer.

Analyzing Data

After scientists complete experiments, they analyze their data. Scientists look at all of the data they have collected. The high and low values give them the range of the results. Scientists may calculate data averages. Averages even out natural variations that occur when measures are made across time or across individuals. The average provides scientists with an approximation of a “true” value for the measure.

Mouse Number Length of Swim Path, Day 1
1 56 cm
2 45 cm
3 49 cm
Average (56+45+49)/3 = 50 cm

Interpreting Data

Graphs help scientists interpret their results by providing a picture of the results. Scientists use graphs to identify trends or patterns in the results of their experiments.

Drawing Conclusions

Because the hypothesis and experiment are based on a research question, you should ask:

Do the results from the experiment provide an answer for the research question?

If the answer is "No" or "I don't know," the experiment probably was not designed correctly. Think about the question and re-design the experiment.

If the answer is yes, ask:

Do the results support the hypothesis?

Whether the answer is "Yes" or "No,” the research question has been answered. Use evidence from the experiment to defend that answer.

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