Genetic markers are features located in specific regions of a chromosome that allow distinction between individuals, populations or species, and are considered representative of changes in the genome. Genetic markers consist of two types: morphological and molecular. Morphological markers have been widely used since they are easily monitored by visual analysis. However, they have several limitations, including their limited number and alterations by environmental, epistatic and pleiotropic interactions, which turned researchers’ attention towards molecular markers in recent years. Molecular markers are not affected by environmental interactions, epistatic or pleiotropic effects, and can be used regardless of the type of tissue. They can be classified as biochemical (isozymes) or DNA markers, and since isozymes also have some limitations, many efforts are made to develop new and more precise DNA markers. DNA markers can be divided into two categories: hybridization-based markers, like Restriction Fragment Length Polymorphism (RFLP) and Variable Number of Tandem Repeats (VNTRs); and PCR-based markers, like Random Amplified Polymorphic DNA (RAPDs), Inter-Simple Sequence Repeats (ISSRs) and Simple Sequence Repeats (SSRs).
In my project, I use microsatellites (SSRs) to perform population studies in native and invasive ranges and compare between the two in an effort to elucidate A. longifolia’s invasive process. I have also worked previously with ISSRs. In a nutshell, DNA is extracted from the leaves (phyllodes) collected from different regions and segments of the genome are amplified through the Polymerase Chain Reaction (PCR) by using specific primers. Results are usually visualized through an electrophoresis.
The image shows an example of PCR amplification with ISSR and microsatellite markers
Adapted from:
Vicente, S. (2016). Assessment of genetic variability in the exotic invasive species Acacia longifolia using molecular markers (MSc Dissertation). Faculdade de Ciências da Universidade de Lisboa, Portugal.
Vicente, S., Máguas, C., & Trindade, H. (2018). Genetic diversity and differentiation of invasive Acacia longifolia in Portugal. Web Ecology, 18, 91-103.