Summary

Since Gregor Mendel’s discovery of genes of genes in the late 19^th century, we have known genes to be the source of inherited traits.  Some of these traits are behavioral as Walter Rothenbuhler found through his study of honey bees.  Technological advancements in molecular biology over the past few decades have allowed us to manipulate specific genes and observe its effect on a particular behavior, allowing us to better understand their relationship.  In this blog series, I shared with you several intriguing discoveries between genes and behavior.  To conclude, in my final blog post, I would like to recap with you these findings.

Circadian Rhythm:  Using the fruit fly, the circadian rhythm, the internal biologic clock that operates on a 24-hour cycle, was found to be controlled by the “period” gene and genes with similar function have been found in the mammal.  Different types of mutations in the “period” gene could have different effect on the circadian rhythm, at times shortening the biological clock and others lengthening it.  Discovery of genes related to the circadian rhythm has allowed us to better understand some human sleeping disorders.

Learning and Memory: Perhaps the most interesting relationship is that between genes and memory as well as learning.  Scientists found that after mutating different genes in the fruit fly, some flies showed difficulty learning or remembering what it has learned.  Flies with a dunce gene mutation were too dumb to learn; flies with a rutabaga gene mutation were unable to form memories; flies with a amnesiac gene mutation were forgetful.  Studies on the mouse also proved that learning or remembering was difficult when an inhibitor which blocked the signals between neurons in the hippocampus was applied.  

Courtship: The courtship behavior is an innate behavior that all animal possess.  The gene that was found to be responsible for the fruit fly’s courtship behavior is the fruitless gene.  Even though male and female fly posses the same fruitless gene, the product of the fruitless gene found be different in sexes (fru^F in the female fly and fru^M in the male fly).  When scientists switched fru^F into fru^M, and fru^M into fru^F, the female fly instead exhibits male courtship behavior toward female flies, and the male fly exhibit an abnormal courtship behavior toward male flies.

Aggression:  Aggression is an innate behavior that is vital to self-preservation.  Studies found that the fruitless gene in the fruit fly also affects its aggressive behavior.  Similar to the fruit fly’s courtship behavior, after switching fruitless gene’s product in the two sexes, the female fruit fly exhibits male aggressive behavior, boxing and lunging, and the male fly exhibits female aggressive behavior, shoving and head-butting.  Furthermore, by using genetically altered mice, scientists were able to activate the mouse’s aggressive behavior simply by turning on a blue light, which would make the mouse attack furiously. 

A myriad of human studies have been carried out and the findings have raised many voices in society.  For instance, the discovery of the “warrior gene”, which is the MAOA gene, is thought to be highly related to human aggressive behavior.  People that were found to posses the warrior gene often exhibit violent behavior such as joining a gang or committing a crime.  Scientists also found “gay gene” (xq28 region), Schizophrenia gene, or a gene (AVPR1A) to be associated with monogamy.  Nature versus nurture theories have long been debated.  Many people now believe that our genetic makeup does not dictate our behaviors, but instead, our behaviors are products of our genes and the environment we encounter throughout our life.