DNA Sequencing

DNA sequencing is the process of determining the exact order of nucleotides in a DNA molecule. It reveals the specific genetic information stored in a gene or genome.

How it works:

One common method is Sanger sequencing. In this process, DNA is first copied in the presence of normal nucleotides and special fluorescently labeled nucleotides called dideoxynucleotides (ddNTPs). These ddNTPs cause the DNA strand to stop elongating when incorporated. Because they are labeled with different colors, the final mixture contains many DNA fragments of different lengths, each ending with a fluorescent tag that corresponds to a specific base (A, T, C, or G). These fragments are then separated by size, and a detector reads the color of each final base to reconstruct the full DNA sequence.

Next-generation sequencing (NGS) allows millions of short DNA sequences to be read at once, making it much faster and useful for large-scale projects like whole genome sequencing.

Applications:

• Identifying mutations or genetic disorders

• Analyzing evolutionary relationships

• Studying gene function and regulation

• Personalizing medical treatments (e.g., in cancer genomics)

How to interpret data: Data from sequencing is typically shown as a series of colored peaks (in Sanger sequencing) or as aligned sequence reads (in NGS). Each letter represents a nucleotide base, and differences from a reference sequence may indicate a mutation or variation.