Biology – 1.2 Concept and uses of classification systems | e-Consult

DNA Sequencing Process: DNA sequencing is the process of determining the precise order of nucleotides (A, G, C, and T) in a DNA molecule. Modern DNA sequencing is typically performed using automated methods, such as the Sanger sequencing method (chain termination method) or Next-Generation Sequencing (NGS).

Sanger Sequencing (Chain Termination): This method involves using DNA polymerase to replicate a DNA template. Modified nucleotides called chain terminators are incorporated into the newly synthesized DNA strands. These terminators halt the DNA synthesis at specific points, creating fragments of varying lengths. These fragments are then separated by size using gel electrophoresis, and the order of the bases in each fragment is determined by analyzing the pattern of the fragments.

Next-Generation Sequencing (NGS): NGS technologies allow for the simultaneous sequencing of millions or even billions of DNA fragments. Various NGS platforms exist, but they generally involve amplification of DNA fragments, followed by sequencing using fluorescently labeled nucleotides or other detection methods. The resulting sequence data is then generated digitally.

Classification using Sequence Data: Once the DNA sequence is obtained, it is compared to the sequences of DNA from other organisms. This comparison is often done using bioinformatic software and databases. The software aligns the sequences and identifies regions of similarity and difference.

Role of Computer Analysis: Computer analysis plays a crucial role in classifying organisms based on DNA sequences. Bioinformatics tools are used to:

• Align Sequences: Align DNA sequences from different organisms to identify regions of similarity and difference.
• Build Phylogenetic Trees: Construct phylogenetic trees that depict the evolutionary relationships between organisms based on sequence data. These trees are built using algorithms that analyze the patterns of mutations and sequence changes.
• Compare to Databases: Compare the DNA sequence of an unknown organism to DNA sequences in existing databases to determine its classification.
• Identify conserved regions: Identify regions of DNA that are highly conserved across species, indicating important functional elements.