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In humans, a molecular genetics study normally begins with the collection of a DNA sample
from the participants in the study, usually by taking some cells from the inner surface of the
cheek. In the lab, the DNA is extracted from the sampled cells and is combined with a solution
containing a marker for the particular genes of interest as well as a fluorescent dye. If the gene is
present in the DNA of the individual, then the solution will bind to that gene and activate the
dye. The more the gene is expressed, the stronger the reaction.
In one common approach, DNA is collected from people who have a particular personality
characteristic and also from people who do not. The DNA of the two groups is compared to see
which genes differ between them. These studies are now able to compare thousands of genes at
the same time. Research using molecular genetics has found genes associated with a variety of
personality traits including novelty-seeking (Ekelund, Lichtermann, Järvelin, & Peltonen,
1999), [10] attention-deficit/hyperactivity disorder (Waldman & Gizer, 2006), [11] and smoking
behavior (Thorgeirsson et al., 2008). [12]
Reviewing the Literature: Is Our Genetics Our Destiny?
Over the past two decades scientists have made substantial progress in understanding the
important role of genetics in behavior. Behavioral genetics studies have found that, for most
traits, genetics is more important than parental influence. And molecular genetics studies have
begun to pinpoint the particular genes that are causing these differences. The results of these
studies might lead you to believe that your destiny is determined by your genes, but this would
be a mistaken assumption.
For one, the results of all research must be interpreted carefully. Over time we will learn even
more about the role of genetics, and our conclusions about its influence will likely change.
Current research in the area of behavioral genetics is often criticized for making assumptions
about how researchers categorize identical and fraternal twins, about whether twins are in fact
treated in the same way by their parents, about whether twins are representative of children more
generally, and about many other issues. Although these critiques may not change the overall
conclusions, it must be kept in mind that these findings are relatively new and will certainly be
updated with time (Plomin, 2000). [13]