DNAröðun

DNAröðun, or DNA sequencing, is the laboratory technique used to determine the precise order of nucleotides within a DNA molecule. The information obtained reveals the genetic instructions encoded in the sequence of adenine, thymine, cytosine, and guanine bases and forms the basis for understanding genes, regulation, and genome structure.

Historically, Sanger sequencing, developed by Frederick Sanger and colleagues, uses chain-termination chemistry to generate labeled fragments read to derive the sequence. It is accurate for short reads and remains a reference method for small-scale projects.

Next-generation sequencing technologies enable massively parallel sequencing, producing millions to billions of reads. Major platforms include Illumina, which provides short, highly accurate reads; PacBio and Oxford Nanopore, which offer long reads and real-time sequencing.

In a typical workflow, DNA is prepared in a library, sequenced in a run, and the resulting data undergo base calling, quality control, and read processing. Reads are aligned to a reference genome or assembled de novo, and variants are called and annotated. Output formats commonly include FASTQ for reads, BAM/CRAM for alignments, and VCF for variants.

DNAröðun has wide applications in clinical diagnostics, cancer genomics, infectious disease surveillance, population genetics, agriculture, and evolutionary biology, as well as forensics. Challenges include handling large data volumes, computational requirements, technology-specific error profiles, interpretation of results, cost, and privacy considerations.

The technique has evolved since the 1970s, with rapid advances in sequencing speed, read length, and accessibility, enabling increasingly routine genomic analysis across research and medicine.