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What is the difference between de novo sequencing and re-sequencing?

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The impact of the Human Genome Project on cancer research — Human Genome Project The Human Genome Project, which operated from 1990 to 2003, provided researchers with basic information about the genetic content of the human organism, opening new avenues of discovery in fields such as cancer research.

In the context of whole genome sequencing, the primary difference between de novo sequencing and re-sequencing lies in whether a reference genome already exists for the organism being studied.

De novo sequencing: This process involves assembling a genome for the very first time. Because there is no existing map to guide the reconstruction, it is a complex task that requires sophisticated computer programs to stitch together DNA fragments. This method was essential for the Human Genome Project, which aimed to create high-quality reference sequences that would serve as a foundation for future research.1
Re-sequencing: This approach is used when a reference genome has already been established. Instead of building a sequence from scratch, researchers produce short DNA sequences and align them computationally to the existing reference. This method is a hallmark of many next-generation sequencing technologies, allowing for the efficient identification of variations within a genome.1

While de novo sequencing provides the initial blueprint, re-sequencing allows scientists to compare individual genomes against that blueprint to identify genetic differences and variations.1