The primary method used by the HGP to produce the finished version of the human genetic code was map-based, or BAC-based, sequencing. BAC is the acronym for "bacterial artificial chromosome.
The fragments are cloned in bacteria, which store and replicate the human DNA so that it can be prepared in quantities large enough for sequencing. If carefully chosen to minimize overlap, it takes about 20, different BAC clones to contain the 3 billion pairs of bases of the human genome. Using this approach ensures that scientists know both the precise location of the DNA letters that are sequenced from each clone and their spatial relation to sequenced human DNA in other BAC clones.
For sequencing, each BAC clone is cut into still smaller fragments that are about 2, bases in length. These pieces are called "subclones. The products of the sequencing reaction are then loaded into the sequencing machine sequencer.
The sequencer generates about to base pairs of A, T, C and G from each sequencing reaction, so that each base is sequenced about 10 times. A computer then assembles these short sequences into contiguous stretches of sequence representing the human DNA in the BAC clone.
This was intentionally not known to protect the volunteers who provided DNA samples for sequencing. The sequence is derived from the DNA of several volunteers. To ensure that the identities of the volunteers cannot be revealed, a careful process was developed to recruit the volunteers and to collect and maintain the blood samples that were the source of the DNA.
The volunteers responded to local public advertisements near the laboratories where the DNA "libraries" were prepared. Candidates were recruited from a diverse population. The volunteers provided blood samples after being extensively counseled and then giving their informed consent. About 5 to 10 times as many volunteers donated blood as were eventually used, so that not even the volunteers would know whether their sample was used.
All labels were removed before the actual samples were chosen. The main goals of the Human Genome Project were first articulated in by a special committee of the U. National Academy of Sciences, and later adopted through a detailed series of five-year plans jointly written by the National Institutes of Health and the Department of Energy.
The principal goals laid out by the National Academy of Sciences were achieved, including the essential completion of a high-quality version of the human sequence. Other goals included the creation of physical and genetic maps of the human genome, which were accomplished in the mids, as well as the mapping and sequencing of a set of five model organisms, including the mouse.
All of these goals were achieved within the time frame and budget first estimated by the NAS committee. Notably, quite a number of additional goals not considered possible in have been added along the way and successfully achieved. Examples include advanced drafts of the sequences of the mouse and rat genomes, as well as a catalog of variable bases in the human genome.
On June 26, , the International Human Genome Sequencing Consortium announced the production of a rough draft of the human genome sequence. In April, , the International Human Genome Sequencing Consortium is announcing an essentially finished version of the human genome sequence. This version, which is available to the public, provides nearly all the information needed to do research using the whole genome.
Genetics Home Reference has merged with MedlinePlus. Learn more. The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health. What is DNA? From Genetics Home Reference. DNA is a double helix formed by base pairs attached to a sugar-phosphate backbone. The human genome is made of 3.
If printed out the 3. If printed out 1 mm apart, the DNA letters in your genome would extend 3, km. Related Content:. What is DNA? What is a gene? What is a chromosome? How helpful was this page? What's the main reason for your rating? Which of these best describes your occupation? What is the first part of your school's postcode? How has the site influenced you or others?
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