Have you ever wondered how we know what genes “look” like? Genes are like instructions, spelt using a code of nucleotides (A, C, G, and T).
Genetic sequencing is a method used to determine the sequence of nucleotides. This “spells” out the gene and allows scientists to read the instruction. Several methods have been developed in the past few decades, each with its own strengths and weaknesses. So, let’s explore some of the most common methods:
Sanger sequencing is a classic method of sequencing that was first developed in the 1970s. This method is based on using fluorescently labelled dideoxynucleosides. The fragments of DNA produced in this way are separated by size, and the sequence can be read off by special machinery. Sanger sequencing is highly accurate and has been used to sequence the entire human genome.
Next-generation sequencing (NGS) is a collective term for several high-throughput sequencing methods that have arisen in the past two decades. NGS methods enable the simultaneous sequencing of millions of DNA fragments in parallel, making it possible to sequence entire genomes in a few days.
Third-generation sequencing refers to a newer generation of sequencing technologies that offer longer read lengths and lower error rates than previous methods. These long reads can be used to sequence highly repetitive regions of the genome and identify structural variants.
Single-cell sequencing enables the sequencing of individual cells. This can help study the genetic differences between tissues and tumours.
In short, not all methods are equal! Different sequencing methods offer varying levels of accuracy, throughput, read length, and cost. Sanger is highly accurate but has low throughput, while NGS methods offer high throughput but shorter read lengths and higher error rates. Third-generation sequencing methods offer longer read lengths and lower error rates but are still relatively expensive. Single-cell sequencing is a specialized method that allows for the sequencing of individual cells.
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