For the Sigma Xi Student Research Showcase

1. B Y : D O R I A N Y A B L I N
M E N T O R : D R . N A N C Y E L W E S S
The Genetic Analysis of High Risk
Athletes for the Presence of the
DRD4 7 Variable Tandem Repeat

2. Research Goals:
 The purpose of this research was to examine the
DRD4 tandem repeats within the three experimental
groups, and determine if there was a higher rate of
DRD4-7 repeats than in the control group.
 The three experimental groups:
 Expeditionary Studies students
 Olympic level bobsledders
 Free soloing rock climbers

3. Research Goals continued:
 Because participants have two copies of this gene,
their genotype results were based on the presence of
the 7 repeat (or more) allele (7+) or absence (7-).
 This study was designed to examine the extent to
which these tandem repeats appeared in the test
controls and hopefully determine if they played a
role in the novelty seeking/thrill seeking activities.

4. Research Goals continued:
 The dopamine receptor D4 (DRD4) expresses a polymorphism in
exon III; the variants in this exon are caused by allelic variations on
the 11th chromosome (Figure 1).
 Changing the number of possible repeats on exon III of the D4
receptor alters the length, structure, and the efficiency of the
receptor (Sander et al., 1997). DRD4 has ten known repeats between
2 and 11 within this exon. The most common repeats being 2, 4 and
7 (Haradon & Galdzicki, 2015).
Figure 1: Dopamine receptor D4 gene. The 48 bp tandem repeat is located within exon 3. Image generated by Dorian Yablin.

5. Hypothesis:
 That the three experimental groups (expeditionary
study majors, international bobsledder, and free
soloing rock climbers) would display a statistical
higher frequency of 7+ repeats than the control.

6. Research methods:
 Cheek cells were collected from participants using 0.9% saline solution.
 Their DNA was then isolated from the solution using the procedures as
outlined in Genetic Origins (Cold Spring Harbor Laboratory).
 The DRD4 polymorphic genotypes were verified through polymerase
chain reaction (PCR) as described in Dreber et al. (2009).
 The PCR primers used were:
 Forward: 5’- GCG ACT ACGTGG TCT ACT CG -3’
 Reverse: 5’- AGG ACC CTC ATG GCC TTG -3’.
 The PCR products were visualized using ultraviolet fluorescence
following migration of samples within 1.2% agarose gels containing
ethidium bromide as explained in Lichter et al. (1993).

7. Research Methods continued:
 Statistical Analysis
 Analysis was done using cross tabulation through SPSS.
Participants were classified according to the presence of (7+) or
the absence (7-) of the repeats founds within exon III of the
DRD4 gene.

8. Data and Results:
 As the level of risk and experience increased to free soloing rock
climbers and Olympic level bobsledders there was a greater
amount of individuals expressing one or both 7+ alleles. Overall
there was a statistically significantly higher amount of 7+
repeats present when the three experimental groups were
combined and compared to the control.
0
10
20
30
40
50
60
70
80
90
100
Control Expeditionary Bobsledders Rock Climbers
PercentAllele
Frequency
7-
7+

9. Data and Results continued:
 If this study were repeated, the survey would be
more extensive, and would ask individuals about any
certifications they have pertaining to these activities.
It would also ask about participant’s level of
expertise in the sport, not just their willingness to
take risk.

10. Conclusion:
 The three experimental groups were chosen
specifically for this study based on the amount of risk
taking that is associated with each group, and the
personalities of the individuals drawing them to
participate in higher risk activities.

11. Conclusion continued:
 When analyzing the results, it was
unexpected to see such low 7+ repeat results
for the Expeditionary Studies group.
 In the survey responses, 65% said they
would be very likely to take risk when
participating in higher risk sports such as
rock climbing, or white water kayaking.
 After isolating and analyzing the
participant’s saliva samples, only 7.69% of
the participants contained a single or double
allele of the 7+ repeat variant
Expeditionary Studies students
taking a lunch break in Scotland,
Image by Dorian Yablin

12. Conclusion continued:
 There are many different possibilities as to why the research
yielded an insignificant difference between the Expeditionary
Studies group, and the control.
 What was not taken into consideration during the study was
the level of expertise the Expeditionary Studies group had. In
the outdoor industry there are various types of certifications
awarded to individuals who prove their ability to do certain
high-risk sports under different circumstances.
 Both the international bobsledders and free soloing rock
climbers are competing at the highest level of expertise in
their sport. The Expeditionary Studies group is still learning
the proper techniques to safely participate in the various high-
risk sports.

13. Acknowledgments:
Thanks to Dr. Thomas Wolosz for his assistance with
the statistical analysis.
And to Dr. Nancy Elwess for all of her guidance.

14. References:
Cold Spring Harbor Laboratory. Genetic Origins. Retrieved on January 19, 2016 from:
http://www.geneticorigins.org/mito/mitoframeset.htm
Dreber, A., Apicella, C.L., Eisenberg, D.T.A., Garcia, J.R., Zamore, R.S., Lum, J.K., and Campbell,
B. (2009). The 7R polymorphism in the dopamine receptor D4 gene (DRD4) is
associated with financial risk taking in men. Evolution and Human Behavior, vol 20:2,
p. 85-92. http://www.sciencedirect.com/science/article/pii/S1090513808001165
Haradon, Z., & Galdzicki, M. (2015). DRD4 Repeats. Retrieved from http://hivebio.org/projects/
drd4-repeats/
Lichter, J. B., Barr, C. L., Kennedy, J. L., Tol, H. H. M. V., Kidd, K. K., & Livak, K. J. (1993). A
hypervariable segment in the human dopamine receptor D4 (DRD4) gene. Human
Molecular Genetics, 2(6), 767–773. http://doi.org/10.1093/hmg/2.6.767
Sander, T., Harms, H., Dufeu, P., Kuhn, S., Rommelspacher, H., & Schmidt, L. G. (1997).
Dopamine D4 receptor exon III alleles and variation of novelty seeking in alcoholics.
American Journal of Medical Genetics, 74(5), 483–487.