Do genes really control behavior?

In my previous blog entry, I gave examples that made people wonder whether genes are responsible for an animal’s or our own behavior.  This idea was further enhanced by an important discovery in 1964.

Walter C. Rothenbuhler was an American Zoologist that studied honey bees and observed interesting behaviors among these honey bees.  He made his discoveries when he was tasked to breed a new line of honey bees with both a high survival rate and honey production.  He focused on two different species of honey bees - the “Brown” line and the “Van Scoy” line.  The Brown honey bees, which he defined as hygienic, will uncap the lid from a comb of brood and remove the larvae inside if they  found them infected.  The Van Scoy honey bees (non-hygienic), on the other hand, will not.  This cleansing behavior of the Brown honey bees greatly increases their colony survival rate, which was proven when Rothenbuhler manually infected a portion of the two colonies’ larvae.  However, the Van Scoy honey bees produce more honey than the Brown honey bees.  (Picture below shows how Rothenbuhler manually infects the larva) 

 

In his attempts to create a honey bee that had both high survival rates as well as high honey production, Rothenbuhler cross-bred the two line of bees.  After many generations of breeding, he discovered four different kinds of behavior among various lines of these offspring.  Two of these lines behaved similarly to their parents - hygienic like the Brown bees and non-hygienic like the Van Scoy bees.  However, the other two types of bee lines exhibited entirely different kinds of behavior.  One of them, named “uncappers”, would only uncap the lid of the comb but would not remove the infected larva inside.  The other ones, named “removers”, seems to behaved the same way as the Van Scoy bees (non-hygienic but when Rothenbuhler uncapped the lids of the combs manually, the removers would go inside the comb and remove the infected larva.

Those who are familiar with genetics would know that this cross-breeding technique is the fundamental way of breeding a line with the specific gene responsible for a specific phenotype (an observable characteristic or trait of an organism).  Even though this technique can be dated back to Gregor Johann Mendel, the "father of modern genetics" and discoverer of the “laws of Mendelian inheritance”, of the 19^th century, it is still widely used in many labs throughout the world today.

Prior to the discovery of techniques to study molecular biology, scientists were unable to isolate and identify the specific genes that were responsible for certain types of phenotypic behavior.  However, thanks to rapid developments in the world of molecular biology over the half-century, scientists today are able to not only isolate and identify genes of interest ,but also further manipulate those genes and observe the resultant behaviors in an animal. 

Without a doubt, genes do play a role in animal, and likely human, behavior.  What is still widely debated is how far does this phenomenon go?  How specific?  Are genes the entire fabric of our nature and dictate all our actions?  Or are genes only the first step in a series of reactions?  Will a mutation in a specific gene cause a dramatic change in certain behavior?  Through continued research, scientists have begun to shed light on these interesting questions.  (To be continued…)