VIDEO: How to Sequence a Genome

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.

Follow Natalie Wolchover on Twitter @nattyover

Natalie Wolchover was a staff writer for Live Science from 2010 to 2012 and is currently a senior physics writer and editor for Quanta Magazine. She holds a bachelor's degree in physics from Tufts University and has studied physics at the University of California, Berkeley. Along with the staff of Quanta, Wolchover won the 2022 Pulitzer Prize for explanatory writing for her work on the building of the James Webb Space Telescope. Her work has also appeared in the The Best American Science and Nature Writing and The Best Writing on Mathematics, Nature, The New Yorker and Popular Science. She was the 2016 winner of the  Evert Clark/Seth Payne Award, an annual prize for young science journalists, as well as the winner of the 2017 Science Communication Award for the American Institute of Physics.