How were short DNA fragments assembled into a complete genome sequence?

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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.

To assemble short DNA fragments into a complete genome sequence during the Human Genome Project, scientists primarily utilized two methods: hierarchical shotgun sequencing and whole genome shotgun sequencing.1

Hierarchical Shotgun Sequencing: This approach involved cloning segments of genomic DNA and arranging them into ordered arrays called physical maps. These maps broke large genomes into thousands of manageable, short fragments. By aligning these fragments where their sequences overlapped, researchers could link them together to reconstruct the full-length genomic sequence.1
Whole Genome Shotgun Sequencing: This method bypassed the creation of physical maps. It involved randomly fragmenting native or cloned DNA into short segments, which were then amplified using bacterial plasmids.1

In both approaches, the final assembly process relied on sophisticated computer programs and powerful supercomputers to stitch the sequences back together. This was a significant challenge, particularly because repetitive elements within complex genomes often created ambiguity during the alignment process.1