SCIENCE THE CORNELL DAILY SUN | Wednesday, February 8, 2012 13

In an effort to simplify the process of diagnosing dis-eases caused by such pathogens as tuberculosis, chlamydia,gonorrhea and even HIV, Prof. Dan Luo, biological andenvironmental engineering, and Prof. Edwin Kan, electri-cal and computer engineering, have combined inventionsfrom their respective fields to potentially revolutionize theway diseases are detected in the developing world with anew handheld device.In Luo’s laboratory, he and his team have developed a

way to amplify the size of small samples of pathogenDNA, RNA and proteins, said Luo. His team hasobserved that DNA formations are analogous to Legoblocks in that a strand of DNA can connect to anotherstrand of DNA if the two contain complementary geneticcodes. The strands can be shaped into different forms. “IfDNA strands that correspond are combined over only aportion of their length, then interesting shapes can bemade, such as the letter Y,” Luo said.The base of the Y shape, the part that points straight

down, is either a strand of DNA or an antibody, designedto connect with a pathogen, just like two Lego blocks con-nect when corresponding parts are brought together Luosaid. The top section of the Y, the part that consists of thetwo outward pointed lines, is the site where moleculescalled monomers attach and chemically combine witheach other in a process called polymerization. Themonomers polymerize when exposed to ultraviolent light. The “Y” detects various pathogens by matching and

connecting with them. When a pathogen is added to asolution of the corresponding Y-shaped molecules, a partof the pathogen will attach to a matching stem on the Y.“So if a pathogen is present in solution, the result is theformation of many double-Ys linked together by a

pathogen molecule, each assembly carrying two moleculescapable of polymerizing,” Luo said.Then, when the mixture is exposed to UV light, poly-

merization occurs, meaning the Y-shaped molecules linkup to each other and form long polymer chains. If poly-merization does not occur, then no pathogen is present.“The polymerization won’t happen if there is no pathogenpresent to link two Ys together,” Luo explained. “A single

Y with only one polymer molecule attached can only linkto one other single Y, and no chain will form.”Kan’s research has made an important implementation

to this new method. He has designed a computer chip thatresponds to the amplified samples targeted by Luo’smethod, and sends a signal that tells scientists whether ornot a pathogen is present.Typically, when a strand of Y-shaped DNA attaches to

a single molecule, a very weak signal is emitted, and itrequires highly tuned and precise sensors to detect apathogen. If polymerization occurs, however, the signalbecomes stronger and easier to detect.Kan’s chip uses common, inexpensive semiconductor

technology compatible with other common electronicdevices, such as a mobile phone. Kan’s device is capable ofmeasuring both the mass and charge of molecules, twomeasurements that can determine whether the Y chainscontain pathogen particles.Kan and Luo’s work on their joint invention is sup-

ported by the Bill & Melinda Gates Foundation as part ofthe Grand Challenge program to develop “point-of-carediagnostics” for developing countries that do not have thelaboratory and research space to test and diagnose diseases.According to Luo, the foundation has distributed $25 mil-lion to 12 teams, with each team working on a differentelement to include in a practical, durable and low-costtesting and diagnostic kit.

By MARIA MINSKERSun Senior Writer

Maria Minsker can be reached at mminsker@cornellsun.com.

The classic explorer, valiantly sails outto discover new lands, penciling in theblank edges of the map, may no longerhold a place in today’s society. But, in thisexplorer’s absence emerges a modernadventurer who traverses the world, fillingin not the missing parts of the globe, butrather the gaps in the map of human exis-tence.Spencer Wells, Frank H.T. Rhodes

Class of ’56 Professor and Explorer-in-Residence at National Geographic andDirector of the Genographic Project, hasadventured to almost 80 countries, riddenex-Soviet tanks in -70 degree temperaturesin far-eastern Russia, traversed the worstpart of the Sahara Desert in Chad andcrossed mine fields in Bolivia, while on aquest to discover how the human racemigrated the globe. The goal of the ongoing Genographic

project is to understand human originsand the genetic relations that are commonto all people, according to Wells.The project analyzes in particular the

genes of remote populations along the SilkRoad, from London to Mongolia, which isa region that has seen substantial humantraffic throughout history. These popula-tions often have relatively “old genes”according to Wells, which means thatthese groups have reproduced minimallywith other populations since ancient timesand thus their genes represent an older,purer version, similar to that of humani-ty’s oldest ancestors.“The core of the science in this project

is based on the work we do around theworld with indigenous and traditionalpeoples,” Wells said. “Because they retainthat geographic link back to their ances-tors that most of us have lost that recentlybecause our ancestors have moved aroundso much.”By examining the number of genetic

differences in populations and factoring inthe normal rate of genetic mutation, hecan determine how long a population hasbeen in a certain region and throughwhere it traveled to get there.

Unlike other academic geneticists,Wells gets to meet the people who givetheir samples to the Genographic projectwhile in the field. In doing so he gets tobetter understand the cultural patterns

behind each sample, he said.“It’s amazing being able to piece the

story of human migration together bymeeting the people who provided theclues,” Wells said.In conducting the Genographic pro-

ject, Wells found that humans are 99.9percent genetically similar to each other.The superficial differences between peopleare the result of small variation in only afew genes.From the initial pool of genes, super-

ficial changes have been those evolution-arily advantageous for survival in specificregions. For example, pale skin is neces-sary for sufficient vitamin D productionin areas where there is little direct lightand similarly, dark skin is advantageousin areas of relentless solar radiation.Other changes, such as hair type, can beattributed to sexual selection amongindividual populations, Wells said.Thegenetic homogeneity of Homo sapienscan be contributed to a near extinction

event 70,000 years ago. At this time,there were only a few thousand humansalive in the world, all of them living inAfrica. When compared with the rest of the

large apes, who have between four and 10times more within-species diversity thanhumans, people are significantly moresimilar than outward appearances wouldsuggest.

“I think this message of people beingmuch more closely connected geneticallythan we might suspect by looking at sur-face features is an important social mes-sage that to me can't be overstated.”

To learn more about Spencer Wells andThe Genographic Project check out ourinterview with the National GeographicExplorer at cornellsun.com/video.

By SHAUNTLE BARLEYSun Staff Writer

Indigenous Genes | Prof. Spencer Wells has traveled to close to 80 countries collecting samples from native peoples. COURTESY OF NATIONAL GEOGRAPHIIC

Academic Adventurer | Prof. SpencerWells is a National Geographic reporter anddirector of the Human Genographic project.

Shauntle Barley can be reached at skim@cornellsun.com.

Prof.Spencer WellsTraces the Path of the

Human Race

New Portable Device Identifies Pathogens

Pathogen Pair | Prof. Edwin Kan and Prof. Dan Luoexamine their pathogen detecting device.

KELLY YANG / SUN STAFF PHOTOGRAPHER

COURTESY OF NATIONAL GEOGRAPHIC