The Human Genome Initiative (HGP) was an international scientific research project that aimed to determine the base pairs that make up human DNA, as well as to identify and map all of the human genome’s genes, both physically and functionally. It is still the greatest collaborative biological effort in the world. After the US government picked up the idea in 1984, the project was formally launched in 1990, and it was declared complete on April 14, 2003. In May 2021, the level “full genome” was achieved.
The Human Genome Project originally aimed to map the nucleotides contained in a human haploid reference genome (more than three billion). The “genome” of any given individual is unique; mapping the “human genome” involved sequencing a small number of individuals and then assembling to get a complete sequence for each chromosome. Therefore, the finished human genome is a mosaic, not representing any one individual. The utility of the project comes from the fact that the vast majority of the human genome is the same in all humans.
Applications and proposed benefits
The sequencing of the human genome holds benefits for many fields, from molecular medicine to human evolution. The Human Genome Project, through its sequencing of the DNA, can help us understand diseases including: genotyping of specific viruses to direct appropriate treatment; identification of mutations linked to different forms of cancer; the design of medication and more accurate prediction of their effects; advancement in forensic applied sciences; biofuels and other energy applications; agriculture, animal husbandry, bioprocessing; risk assessment; bioarcheology, anthropology and evolution. Another proposed benefit is the commercial development of genomics research related to DNA based products, a multibillion-dollar industry.
The sequence of the DNA is stored in databases available to anyone on the Internet. The U.S. National Center for Biotechnology Information (and sister organizations in Europe and Japan) house the gene sequence in a database known as GenBank, along with sequences of known and hypothetical genes and proteins. Other organizations, such as the UCSC Genome Browser at the University of California, Santa Cruz, and Ensembl present additional data and annotation and powerful tools for visualizing and searching it. Computer programs have been developed to analyze the data because the data itself is difficult to interpret without such programs. Generally speaking, advances in genome sequencing technology have followed Moore’s Law, a concept from computer science which states that integrated circuits can increase in complexity at an exponential rate. This means that the speeds at which whole genomes can be sequenced can increase at a similar rate, as was seen during the development of the above-mentioned Human Genome Project.
Techniques and analysis
The process of identifying the boundaries between genes and other features in a raw DNA sequence is called genome annotation and is in the domain of bioinformatics. While expert biologists make the best annotators, their work proceeds slowly, and computer programs are increasingly used to meet the high-throughput demands of genome sequencing projects. Beginning in 2008, a new technology known as RNA-seq was introduced that allowed scientists to directly sequence the messenger RNA in cells. This replaced previous methods of annotation, which relied on the inherent properties of the DNA sequence, with direct measurement, which was much more accurate. Today, annotation of the human genome and other genomes relies primarily on deep sequencing of the transcripts in every human tissue using RNA-seq. These experiments have revealed that over 90% of genes contain at least one and usually several alternative splice variants, in which the exons are combined in different ways to produce 2 or more gene products from the same locus.
The genome published by the HGP does not represent the sequence of every individual’s genome. It is the combined mosaic of a small number of anonymous donors, of African, European and east Asian ancestry. The HGP genome is a scaffold for future work in identifying differences among individuals. Subsequent projects sequenced the genomes of multiple distinct ethnic groups, though as of today there is still only one “reference genome.