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Kay Phillips, an associate professor in the Department of Pediatrics at U of L, is a behavioral geneticist. And, having been one for a number of years, she is used to explaining exactly what that is to nearly everyone she meets outside the field. "Behavioral genetics is the study of behavioral traits from the point of view of genetics, or how genes influence behavior," she says. "It covers humans and experimental organisms. Most studies on animals have been conducted on laboratory mice and fruit flies."
Phillips could go on to describe those studies and their findings in detail, because they have contributed greatly to the field and to her ability to conduct her current research. But she understands that most people don't get excited about the behavior of fruit flies, so she sticks to the subject of human behavioral genetics, which offers something of interest for just about everyone, because it teaches us about ourselves.
"Genetics itself is a relatively new field," Phillips says. "We didn't even know that DNA was the material of inheritance until a few decades ago. Behavioral genetics is even newer, but recently it has become obvious that genes do play a significant role in human and animal behavior. As we work to better understand that role, behavioral genetics is coming into its own as a scientific field of study."
Since arriving at U of L 10 years ago, Phillips has been a faculty member with the Louisville Twin Study. She is looking for clues to how genes influence human temperament by studying the behavior patterns of twins and their siblings. Phillips has brought new funding to the study, and has taken its research in a new direction.
In 1993, Phillips and her colleagues, biochemist Mark Brennan and psychologist Adam Matheny, received initial funding from the National Institutes of Health (NIH) for a comprehensive search for the genes that influence human behavior. By studying the genetic patterns of twins and siblings, they are looking for the genes that contribute to individual differences in personality, temperament, and cognitive abilities.
"There is already a great deal of evidence that genes influence human behavior," Phillips explains, "so it makes sense to try to find the particular genes that influence specific behaviors. That wasn't possible in the past, but we now have the technology to isolate those genes using DNA analysis."
Twins offer scientists a unique opportunity to explore the influence of heredity and environment on human behavior. Identical twins, formed when a single fertilized egg divides to become two individuals, are genetically alike. Therefore, it can be assumed that their behavioral differences will be related to environmental factors. Fraternal twins, produced when two eggs are fertilized simultaneously, are, on average, 50 percent genetically similar, so their behavioral differences are likely to be a mixture of genetics and environment. Phillips' project, the Louisville Twin Family Study, involves the collection of blood samples from twins and family members to analyze their DNA patterns. Each person also completes a questionnaire that covers several hundred items related to personality and temperament. "We're mapping the genes of the families, and analyzing the DNA samples to look for similarities," says Phillips. "We want to find out if genetic similarities are associated with similarities in behavior, such as activity level, extroversion, or shyness, as well as cognitive abilities such as vocabulary skills and arithmetic skills."
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Using the "sibling pair method" of genetic linkage, Phillips is looking for genetic similarities between siblings that correlate with similarities in behavior.
"We want to determine what two siblings received from their parents that was exactly the same and what they received that was different on a particular chromosome," Phillips explains. "If siblings behave similarly on a particular trait, and they received the same genes from their parents at a particular spot on a chromosome‹and if that relationship holds up across hundreds of sibling pairs then there is strong evidence that there's a gene that influences that trait at that spot on the chromosome."
Now entering its fifth year, Phillips' study has been funded for a total of $4.4 million, making it one of the largest NIH grants ever received for a single research project at U of L. This type of research requires many hundreds of sibling pairs, Phillips says, and the Twin Study has provided an existing base for participant recruitment.
"We now have 1,000 sibling pairs," Phillips says, "and we're just getting started. It's been cost-effective to use the twin families for the gene mapping project because we already know so much about their behavioral development. Having those data has saved us years of work."
By the end of the study, Phillips plans to map the genes of over 2,000 sibling pairs. Part of her latest grant from the NIH will help her recruit the spouses and children of twins and siblings who are already in the study. This will mean the opportunity to study three generations of families the original twin and sibling participants, their parents, and their children.
The families have responded positively to the new study, Phillips says. "They know that this study will help us better understand human development and find genes that can cause problems," she says. "They've let us study them and take away their time in order to help other people. Not everybody would allow us to do that, especially for decades." In exchange, Phillips has gone to great lengths to protect the families' privacy. The DNA analysis is conducted with strict confidentiality. Staff members never see the DNA results. And lab technicians who analyze the DNA do not know who the participants are. All samples are identified by codes that only faculty can connect to the individuals. Phillips has begun preliminary data analysis, but results will not be definitive until the DNA testing is complete.
"We don't want to run a lot of statistics on the data until we have a large enough sample to detect what we're looking for," she says. "We want to avoid rushing out to report what may turn out to be false positives. I think we'll learn that there are specific genes that influence behaviors, but we won't know for sure until we find them." If those genes are found, Phillips says, it does not mean that people are destined to exhibit certain behaviors.
"Influence is a key word," says Phillips. "Genes influence, not dictate, behavior. Behavior is also influenced by environment, and by free will. Genetics does not by any means take away free will."
Phillips says she hopes this study will contribute to a better understanding of human development and new treatments for behavioral disorders. She also recognizes that behavioral genetics is uncovering completely new and sometimes frightening information. "The knowledge we gain will give us a lot of opportunities but some of it will be difficult for people to deal with," she says. "Science will grow, medicine will grow, and our awareness of ourselves will grow. But for some people knowing that much about themselves may be scary so, as we find new ways to gather genetic information, we're going to have to help people cope with that. Genetic counseling and education will help people interpret this information and learn to use it within their daily lives."
Adapted from an article in Et Ultra, the magazine of research and scholarship at U of L.
