Causes of the Behavior of Transgenic Mice

Causes of the Behavior of Transgenic Mice
Selectively manipulating genes can lead to a greater understanding of molecular and cellular brain functions and behaviors. However these specific gene mutations may trigger compensatory changes that mask a phenotype or adds to it. Therefore it might be difficult to determine the specific effect of a mutation on behavior. This is especially true since a mutation may be affected by the environment or a specific genetic background.
Because of this it is important to find the best way to understand and interpret behavioral data. The Morris Swimming task is a task where the animals are encouraged to find a platform in a water tank. Through careful examination it was found that there where several behavioral trends. One of them is called thigmotaxis and it refers to the mice swimming near the wall without even trying to find the platform. This has to be overcome in order to achieve the goal. If it is not overcome then the stage where the animal learns the location of the platform cannot be reached. A generalized interpretation of the mutant animal?s behavior might lead us to believe that it cannot achieve its task because of learning and memory impairment however it can be observed that the reason for its failure might be its inability to overcome its initial behavior. To verify that this is the cause of the animal?s behavior there is a technique called pca. This technique allows researchers to correlate specific measures of the animal?s movements with various factors such as thigmotaxis to understand the specific causes of the behavior and how the mutation affects the animals. It has been found that 50% of the source of variation of the animal?s behavior is the inability to overcome thigmotaxis and is not related to its inability to perform learning tasks.

To understand the specific effects of the mutation on animals one must also be careful to eliminate genetic background and environment as affecting performance. A Meta analysis of the data for the water task has shown that both environmental and genetic effect produce sufficient variation to account for the range of almost all behavioral measures. It is hard to determine the effects of the mutation alone without it being confused with effects from other sources. It is helpful to test inbred animals where heterozygous animals are mated to produce wild-type and homozygous offspring. To limit the effects of environment it is helpful to test mice raised in the same litter. These mice should also be backcrossed so that offspring are mated with the inbred strain so as to preserve the effects of the mutation. However many strains show specific peculiarities so that the results cannot be generalized to other strains. There should be at least two strains tested with the mutation to avoid this. There is also a phenomenon known as hybrid vigor where the hybrids from inbred strains perform the learning tasks better then their parent. To allow the specific effects of the mutation to be seen it is better to test the F2 mice which do preserve enough hybrid vigor to outperform parental strains but where mutations can be detected if the sample size is large enough.

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