DNA sequencing has changed genetics from a sophisticated guessing game into a hard science. With this tool, biologists are able to locate the molecular code from which traits emerge. They can spot mutations, and from those, trace how similar species evolved apart . Down the road, sequencing will help scientists refine gene therapy techniques to treat disease, and genetic engineering to advance biotechnology.

Gene sequencing is painstaking work, but it's so useful that the full genomes of tens of thousands of organisms have been sequenced over the past 15 years, including all 3.3 billion base pairs of the human genome, which an international collaboration of geneticists sequenced 10 years ago.

To learn how it's done, we start with part 5 of a video tutorial created by the National Human Genome Research Institute. Parts 1, 2, 3, and 4 give some excellent background about the Human Genome Project, DNA, how E. coli bacteria is used to store and replicate segments of human DNA, and how scientists produce the supply that is then used for sequencing. And that last bit is what we're really interested in here: How did scientists learn the sequence of all 3.3 billion base pairs? We'll let the videos do the talking.

Part 5: Preparing DNA for Sequencing

Part 6: Sequencing Reactions

Part 7: Products of Sequencing Reactions

Part 8: Separating the Sequencing Products

Part 9: Reading the Sequencing Products

Part 10: Assembling the Results

Part 11: Conclusion

Got a question? Send us an email and we'll look for an expert who can crack it.

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