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How did whole-genome shotgun sequencing differ from hierarchical shotgun 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.

During the Human Genome Project, two primary strategies were used to sequence large genomes, differing largely in their reliance on physical mapping and computational assembly.1

Hierarchical Shotgun Sequencing

This approach involved breaking the genome into large, manageable segments that were cloned and arranged into ordered arrays known as physical maps. These maps served as a framework to break the genome into thousands of smaller, overlapping DNA fragments. This method was favored for generating high-quality reference sequences because the ordered fragments were easier to manipulate, distribute among laboratories, and subject to rigorous error correction.1

Whole-Genome Shotgun Sequencing

In contrast, this approach bypassed the time-consuming and expensive process of creating physical maps. Instead, the entire genome was randomly fragmented into short segments, which were then sequenced and reassembled using sophisticated computer programs and powerful supercomputers. While this method provided more rapid access to the DNA sequence, the assembly process was significantly more difficult and computationally demanding than the hierarchical approach.1