February 26, 2015

Mathematics Research Group Publishes Result on Genetic Change

A team of Emmanuel College faculty and students have used mathematical modeling to make new predictions about the rate of genetic change in a spatially structured population, the findings of which were published this month in PLoS Computational Biology.

A team of Emmanuel College faculty and students have used mathematical modeling to make new predictions about the rate of genetic change in a spatially structured population. Assistant Professors of Mathematics Benjamin Allen and Christine Sample and Professor of Mathematics and Department Chair Yulia Dementieva worked with mathematics majors Christopher Paoletti '15 and Ruben Medeiros '14, as well as Professor of Biology and Mathematics Martin Nowak of Harvard University, to challenge conventional wisdom about how genomes change over time.   

Their findings, "The Molecular Clock of Neutral Evolution Can Be Accelerated or Slowed by Asymmetric Spatial Structure," published February 26th in the journal PLoS Computational Biology, concern neutral or "silent" mutations-random genetic changes that do not affect the organism but can be passed on to offspring.  Fifty years ago, it was discovered that these changes accrue at a predictable rate, forming a kind of "molecular clock."  The idea of a molecular clock is used, for example, to estimate how long ago humans diverged from chimpanzees and bonobos, our closest evolutionary relatives.

The Emmanuel College researchers show that the layout of a population's habitat can change the rate at which this clock ticks. Imagine, for example, a population of birds spread over a cluster of islands.  If one island is particularly fruitful-rapidly producing offspring that spread to other islands-new mutations will accumulate more rapidly than if all birds were mixed together. Over time, this faster rate of change could be visible in the birds' genomes. 

In addition to biological evolution, the researchers also looked at whether the geometry of social networks could affect the success of new ideas.

"We have this idea that our networked world makes ideas spread faster and faster," said Dr. Allen. "But when we looked at real-world Twitter networks, we found that most of them actually reduce the chances of an average idea to gain a foothold.  This happens because, with so much information flying around, ordinary ideas become lost in the shuffle, and only the most compelling ones survive."

This project grew out of the 2013 Emmanuel College summer research program, in which Paoletti and Medeiros participated under the supervision of Drs. Allen, Sample and Dementieva.  

"This research opportunity has given me phenomenal insight and understanding of how mathematics can be applied to biological processes," said Medeiros.  

In addition to the journal publication, this research was also presented by Dr. Sample at the 2014 Joint Mathematics Meetings in Baltimore, Maryland.

View the article here.

Dementieva, Allen, Paoletti '15, Medeiros '14 and Sample with the proof of their main result.

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