Role of Molecular Biology in Evolutionary Classification
One of the primary goals of biological research in the past was to categorize organisms systematically according to their natural relationships. However, the focus has shifted to the elucidation of evolutionary relationships and the importance of information on evolution to the fundamental principles of biological and environmental sciences. To achieve this, fossils are used to collect genetic information of the organism under study and the diversity of nucleic acid molecule among organisms are used as the basis for modern evolutionary classification (Graur, Zheng, & Azevedo, 2015). Currently, scientific techniques such as DNA sequencing and other phylogenetic tools are used to broaden our understanding of the systematics of organisms and evolution.
DNA technology takes center stage in the modern classification, which is based on the similarity of the genome sequence among organisms. DNA sequencing has revealed a great deal of information about the similarity of organisms and their relationships to each other, which makes this technique different from the traditional classification that was based on morphological characteristics. Since the beginning of classification, the greatest challenge has been to define a species based on morphological characteristics (Marakeby, et al., 2014). Therefore, DNA comes in handy to assist in the delineation of species that appear to differ from each other due to the lack of a clear morphological demarcation.
It is true that DNA similarity provides more in-depth information about an organism compared to the use of morphological characteristics. For example, for a long time, the Afro-tropical pierid butterfly was believed to belong to the sub-family Pseudopontiinae, and it was only after an extensive DNA analysis revealed that there are multiple species involved in the complex with little morphological differences. Therefore, a technique such as DNA barcoding is useful in investigating relatedness among organisms by taking short DNA sequence from the genetic samples of the organisms under study. The DNA sequences are recorded in a public genetic database. DNA technology has helped to eliminate the use of a single judgment of one or a few scientists in the identification of species. Besides, it provides an objective evolutionary analysis of an organism because DNA can provide information about how long an organism has existed (National Research Council, 2006).
Genome profiling is a molecular technique used in the identification and classification of organisms, which involves three steps that are a random polymerized chain reaction, temperature gradient gel electrophoresis, and the normalization of data through computer processing. Upon going through these steps, the data collected is used to calculate a pattern similarity score between two genomes and determine the relatedness of an organism by using the similarity of the small rRNA subunits sequence among organism (Kress, 2017). However, the utility of barcoding has come under sharp criticism by a section of taxonomists due to the degree of biases in the technique. For instance, the technique underestimates the intra-species variations (Meier-Kolthoff, Goler, & Klenk, 2014).
Besides, the interspecies variations are overestimated since the related species are not taken into account during analysis, probably due to their absence during sampling. Besides, the use of mitochondrial DNA for analysis of organisms instead of nuclear DNA has been criticized as a biased approach since the nuclear genome comprises of several genes inherited from both parents (Hewitt, Johnstone, & Young, 2013). Therefore, the future of DNA technology in the evolutionary classification will focus on complementing data from mitochondrial DNA and nuclear DNA to produce reliable information in the identification of species.