Fellows Feature: Jaehee Kim


Jaehee Kim is a postdoctoral scholar in the Department of Biology at Stanford University. She received her B.A. in Physics and Mathematics from Columbia University and her Ph.D. in Physics from Stanford University. Her research interests include mathematical properties of admixed population phylogenetic trees inferred by neighbor-joining, the relationship between individual identifiability and ancestry information in CODIS forensic markers and non-CODIS microsatellite loci, and change of admixture fraction in a hybrid population mating assortatively based on phenotype over time. 

Can you tell us a bit about yourself, personally and professionally? 

I was born and grew up in Incheon, South Korea’s third largest city, where I was likely the most physics-y kid on the block. True to form, I received a B.A. in Physics and Mathematics from Columbia University and a Ph.D. in Physics from Stanford University. My graduate research focused on the study of quantum chemical dynamics in complex molecules. I developed an ab initio theoretical framework to numerically simulate light-induced excited state topology and nonadiabatic dynamics, as well as multidimensional statistical techniques to analyze molecular fragmentation patterns. Now, I am a postdoctoral scholar in Noah Rosenberg’s lab.

How did you end up here? What got you interested in genetics and science?

Like most physics-y kids, I always loved math and spent countless hours voraciously reading science magazines and Feynman lectures. I was amazed by how physical phenomena, from mundane everyday events to the creation of the universe, could be explained by beautiful mathematical equations. I believed that everything could ultimately be explained by the laws of physics. During graduate training in atomic molecular optical (AMO) physics, working with people from diverse fields expanded my research interests. After going to a handful of outer department talks, I was drawn to evolutionary biology—like many people, I always have the same age-old questions lingering in the back in my mind: “why are we here; where are we going?” (Charles H. Townes, 1997). The current lab is the perfect fit for me as it applies rigorous mathematical theory and statistical methods to the study of human evolution and population genetics. I still have a lot to learn, but I have been enjoying working in the lab very much so far!

Can you tell us about your current research and what you want to achieve with it? 

My current research deals with the development and application of a mechanistic model for assessing the effect of different admixture histories involving dynamic contributions of mutually isolated source populations on the ancestry of admixed human populations. Human mating is non-random to some degree, since most people marry individuals of roughly similar phenotype and cultural factors. The assortative mating alters genetic variance for the assorting trait and makes the traits more susceptible to selection over time, thereby changing the genetic structure of a population.

Since the ancestry information is propagated through genotype but mating is based on phenotype, mapping genotype to phenotype is a crucial step. Among many interesting results the model produces, correlation between ancestry proportion and phenotype is of particular interest as it gives us insight about the degree to which genetic differences give rise to phenotypic differences between human groups. This also helps us to answer important questions regarding racial classification beyond conventional phenotypic group-level differences that are believed to be a representative of a race or ethnicity, for example, skin and eye color.

Once gaining intuition from the idealized model, to simulate more realistic human population, the model can be further extended by including confounding factors such as dominance, varying heritability, effect size distribution across loci contributing to the quantitative trait, and linkage disequilibrium, as well as environmental perturbations.

Were there people in particular to whom you would attribute your professional success? What is it like working with your current lab advisor and his lab? 

My Ph.D. advisor, Prof. Phil Bucksbaum, has provided me every bit of guidance for becoming a better scientist and encouraged me to collaborate with people outside the physics department to branch out into new research areas. His genuine enthusiasm for science and encouragement kept me motivated when research progress was bumpy. From my graduate lab, Doug taught me the importance of scientific intuition over sets of equations and he has made working in the lab so much more fun and interesting. James showed me reasonable science could be extracted from suboptimal experimental data if you used good statistical methods.

My current advisor, Prof. Noah Rosenberg, believes in the interdisciplinary nature of the work and gave me a chance to work in his lab. He helped me transition smoothly into the new field by providing every possible resource, and guided me through the systematic and mathematical approach for understanding evolutionary biology. I have also enjoyed the camaraderie and benefited from the varied expertise of the group members.

What are your future plans? Where do you see yourself professionally in the next 5 or 10 years?

Long term, I see myself still working in the field of theoretical population genetics. Having my own lab and staying in academia will be the best-case scenario, but I would be happy with government labs or industry as long as I can do meaningful research with some freedom and independence.

What advice would you offer to other grad students or postdocs who are considering pursuing a similar educational and career path as you? 

  • Most physicists are proficient in math and programming, but still, the more the better.
  • Stay open-minded, look outside your department, and explore your options. There are tons of other interesting work going on that could use a physicist!
  • Have patience, and don’t rush. Research takes time, and some projects might not end up working out. Persistence is important, but at the same time, know when to stop and move on, and when to pause for now and come back later.
  • Have a life outside the lab, and cut yourself some slack. You’ll need it for your sanity.

Can you speak a bit to the role you see CEHG playing on Stanford campus?

I love the cross-disciplinary environment CEHG has created. It brings scholars from various fields, which encourages me to communicate with researchers outside my specific research area and broadens my knowledge. I believe the collaborative approach across different fields can produce creative solutions to challenging problems through a diverse array of tools.

For instance, during my graduate studies in physics, I have used techniques borrowed from biology—for example, genetic algorithm and spawning of wavepacket—in modeling complex molecular dynamics. I am excited to apply physics techniques to tackling fundamental problems in evolutionary biology and share my interests with others.

Tell us what you do when you aren’t working on research. Do you have hobbies? Special talents? Other passions besides science? 

I spend most of my free time training in the gym. I have played various sports growing up, but my current focus is in Olympic weightlifting. I also like trying out new fitness classes/workshops/gyms and enjoy reading sports science and physiology research articles.


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