For many scientists, researchers, and members of the public who love technological innovation, the recent announcement of a project to synthesize the human genome can’t help but recall another memorable launch that took place nearly 26 years ago. October 1, 1990, marked the launch of the original Human Genome Project: a ground-breaking, international research collaboration whose goal was the complete sequencing, or mapping, of the human genome. Join us for a look back at this unique project that allowed us, for the first time, to read and understand nature’s complete genetic blueprint for how to build a human being.
What is a genome?
A genome is the term for the complete set of DNA found in a living organism; DNA is the chemical compound that contains the necessary genetic instructions for an organism’s development. DNA molecules have a famous double-helix shape: two twisted and paired strands that are each made up of chemical units called nucleotide bases. Adenine (A), thymine (T), guanine (G), and cytosine (C) are the four bases. In a DNA molecule, the bases located on one of the strands pair with their opposite numbers on the second strand to create what are known as base pairs.
In the human genome, there are approximately 3 billion base pairs, which are located in the 23 chromosome pairs that are contained in the nucleus of each of our cells. Each chromosome in turn contains anywhere from hundreds to thousands of genes, for an estimated total of 30,000 genes in the human genome.
What does sequencing a genome mean?
Sequencing is the process of examining a segment of DNA to determine the precise order of the base pairs on its strands. To do this, the Human Genome Project used a map-based method known as the BAC-method. (BAC stands for “bacterial artificial chromosome.”) The method involves fragmenting human DNA into pieces of a large but manageable size (about 150,000 to 200,000 base pairs each), and cloning these fragments in bacteria, which then store and replicate the human DNA through their natural growth processes until there are large enough quantities of DNA to be prepared for sequencing.
The next step is to map each BAC clone to determine where the DNA it contains has come from within the human genome; this involves cutting each BAC clone into even smaller fragments (called subclones, of about 2,000 base pairs in length), and then running these subclones through a sequencing reaction process. Finally, scientists use a sequencing machine to generate hundreds of base pairs from each sequencing reaction. Computers then assemble the pairs into contiguous sequence stretches that represent the order of DNA in the human genome.
Whose DNA was used for the Human Genome Project?
The Human Genome Project relied upon the DNA of a number of volunteers. Naturally, given the extremely sensitive nature of the genetic information being handled throughout the course of the project, confidentially was a top priority, and researchers took several steps to protect the identity of the volunteers.
Participants were recruited at random through local public advertisements and underwent extensive counseling before consenting to participate and donating blood samples. Before choosing samples for sequencing, researchers removed any identifying labels from the samples. Furthermore, far more volunteers provided blood samples than were eventually used in the project, so even the volunteers themselves did not know whether or not their samples were used.
Has the human genome been completely sequenced?
Our map of the human genome is now as complete as it can be, given the limits of existing technology. About 1% of the portion of the genome that contains genes is unrecoverable by any current sequencing method. To fill in the gaps and obtain the sequence of these sections, new technologies must be invented. However, for the purposes of scientific research, the gene-containing portion of the human genome is essentially functionally complete, thus allowing scientists and researchers to use our newfound, comprehensive understanding of human genetics to improve human health and advance the fields of biotechnology and genetic engineering.
Who owns the human genome?
As a publicly-funded initiative, the Human Genome Project made immediately public every part of the genome that it had sequenced, and it continues to regularly post new genome data. However, in the years following the official completion of the Human Genome Project in April 2003, many thousands of patents on human genes were and continue to be filed by private companies (although because the majority of these patent applications have not yet been acted on, it’s not clear how much of the genome can be freely used today for commercial purposes).