PCR (polymerase chain reaction) amplification of ancient and modern DNA samples can be used by researchers to track migration of animal and human populations, shedding light on evolution and the movement of ethnic groups across continents. There are many different studies that have used this technique, and this post includes a few different examples.

Tracking human migration

Beta thalassemia, an inherited blood disorder, is the most common genetic defect in Lebanon, and a team of researchers at the American University of Beirut found that using PCR to track the mutation cast a light on recent and historic population migration. The team used amplification refractory mutation system (ARMS) PCR or direct gene sequencing to find the genetic mutations causing beta thalassemia in people from different religious backgrounds and different regions.

They found the highest rate of carriers in the Sunni Muslims, followed by Shiite Muslims and Maronites (the largest Christian group in Lebanon). The patterns of mutations within the Muslim groups tied in with migration patterns from nearby Muslim countries. The mutations within the Christian group were similar to those in Macedonia, potentially confirming ancient Macedonian origins for some Lebanese Christian groups. The level of incidence of beta thalassemia also tied in with malaria-infested regions, as the mutation confers some degree of protection against the parasite.

As well as providing information on how the population and the mutation have moved within the region, research of this type will help healthcare workers ensure that screening and prevention programmes are in the right place and targeting the right groups

PCR in fish migration

In a study by a team of Portuguese researchers from the Instituto Nacional Investigação Agrária e das Pescas, a mitochondrial DNA PCR-RFLP marker was used to track the population of the black scabbardfish (Aphanopus carbo), an economically important sea fish. Looking at fish from three locations off the coast of Portugal and the Madeira Archipelago, the researchers found that the fish from the Madeira Archipelago were genetically distinguishable from the other two groups, which seems to suggest that there is a different and possibly isolated population of black scabbardfish in Madeiran waters.

PCR and plant pathogens

The import of plant pathogens is on the increase, largely through trade in foreign and exotic plants. The origin of the fungus Phytophthora ramorum (sudden oak death), which has affected trees in Oregon, California and Europe is thought to be Asia, and ash dieback (Hymenoscyphus pseudoalbidus), a fungal pathogen now in the UK, is likely to have originated in Poland. A team of US researchers used PCR to look at the genetic diversity of Phytophthora ramorum using PCR as part of the process of microsatellite genotyping. Tracking the patterns of genetic diversity showed two migrations eastwards of one of the most common strains; one from Connecticut, Oregon, and Washington, and the other from California. The level of genetic diversity also suggested rapid mutation and genetic drift, and this knowledge could help understand the next steps of plant pathogen migration, and how to prevent or slow this.

Other examples

Suzanne Elvidge is a freelance science, biopharma, business and health writer with more than 20 years of experience. She has written for a range of online and print publications including FierceBiomarkers, FierceDrugDelivery, European Life Science, the Journal of Life Sciences (now the Burrill Report), In Vivo, Life Science Leader, Nature Biotechnology, New Scientist, PR Week and Start-Up. She specialises in writing on pharmaceuticals, biotechnology, healthcare, science, lifestyle and green living, but can write on any topic given enough tea and chocolate biscuits. She lives just beyond the neck end of nowhere in the Peak District with her second-hand bookseller husband and two second-hand cats.