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How do we decipher the human genome?The human genome is a massive
text. If the three billion letters called "bases" that makeup the human DNA in
a cell were printed in telephone books, the stack containing the entire human
genome would be as tall as the Washington Monument. As you can imagine, unraveling
the human genome is no small task. There are many steps involved in deciphering
the human genome, and many different sections within the BCM-HGSC play a very
important role in this process. | |
| Mapping The first step in sequencing the genome is to break chromosomes into fragments of 200,000 bases each. The mapping section is the front end of the process and focuses on selecting the appropriate fragments to sequence. |  |
 | Library
The library section is focused on breaking the 200,000 base fragments into smaller pieces (about 2,000 bases), because DNA sequencing methods do not work on long strands of DNA. This process also includes purifying the 200,000 base fragments, and amplifying these small pieces. |
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Sequencing and Production After DNA is broken into smaller pieces, the next step in the process is to add flourescent colored tags to each of the DNA letters. Each letter A, T, C, G, has an assigned color. This is a Sanger semi-automated process done in a large scale, involving both people and robots. |  |
 | Loading
Once the DNA strands are tagged, the next step in the process is to read the order of each strand in the DNA. The tagged reactions are loaded into specialized sequencing machines, which use lasers to read and record the color of each letter as it passes by in very thin tubes called "capillaries." Because the letters pass by the laser in order, the order of the colors will tell scientists the proper order of the DNA letters. Approximately 500 bases can be read in each DNA sequencing reaction, so about 25 million of these sequences are needed to reach our goals. |
| Assembly
After the proper order of the letters has been determined, powerful computers are used to put the small, 500 base pair DNA pieces back together. Scientists can then piece together a giant puzzle that reconstructs the chromosomes for further analysis. |  |
 | Informatics
The informatics group is involved in every step of the sequencing process. The informatics group is responsible for developing software that is capable of managing and manipulating the enormous amount of data generated at the BCM-HGSC. Some of the responsibilities of the group include: tracking samples, managing and storing tens of millions of sequences, assembling information, and entering this information into a database that can be accessed by the public. |
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of these complex processes play a central role in unraveling the genetic information
contained in the human genome. | |
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