Question

1)

1) What are the “tools”, experiments that behavior geneticists use to demonstrate the role of genetics in bringing about the phenotype (e.g. hybridization, cross-fostering, twin studies, and more)

2) How can you demonstrate that the pineal organ is controlling rhythmicity (consider: Melatonin secretion after lesioning; excise pineal and observe in petri dish)

Answer 1

Behaviour geneticists use a variety of tools to find out how genes shape behaviour. Some of the tools used are discussed below:-

1) Common Gardening - Some of the most initial studies on the nature versus nurture debate on behaviour were conducted on animals. The technique used is called Common Gardening wherein animnals who differ in behavior across their native habitats are placed in a common garden thereby making it possible to separate the environmental from genetic influences. If the animals behave the same when in the common garden, then we can say that the behavioral differences observed across their native habitats are likely due to environment. However, if the differences persist even in a common garden, then we can say that it is the genes that are playing the important role in shaping behaviour.  

2) Cross-fostering - In this technique, the naturally born offspring is separated from the parents at birth and reared by foster parents. For instance, if a child who is separated at birth from his parents & reared by foster parents shows behaviour that is identically similar to his/her biological parents and dissimilar to his/her foster parents, we can then conclude that behaviour is indeed genetically determined. On the contrary, if the child's behaviour is similar to his/her foster parents and dissimilar to his/her biological parents, we will then assume that environment played an imporatnt role in shaping the child's behaviour. In most studies, however, a blend of both genetics & environment have been found to play a role in shaping behaviour.

3) Twin studies- Twin studies are similar to cross fostering experiments. Herein, a researcher compares the similarity of a particular behaviour trait between sets of identical twins who are believed to share all of their genes to the similarity between sets of fraternal twins who are believed to share only 50% of their genes. In this case, any excess likeness between the identical twins points to genes playing a broader role rather than environment.

Another example of a varitaion to twin studies is to study identical twins reared in separate environments. In such a scenario, if the identical twins show great similarity on the behaviour trait being examined despite having been exposed to different environments, we can then say that genes are determining the behaviour.