What is Gene Sequencing?

Mary McMahon
Mary McMahon

Gene sequencing is a process in which the individual base nucleotides in an organism's DNA are identified. This technique is used to learn more about the genome of the organism as a whole, and to identify specific areas of interest and concern. A number of different techniques can be used, including BAC to BAC sequencing, which creates a map of the genome, and shotgun sequencing, which splices together multiple tiny fragments of the genome to get a total picture.

Blood samples may be used to conduct DNA sequencing.
Blood samples may be used to conduct DNA sequencing.

As soon as DNA was identified and its role was understood, researchers started sequencing it, because they were interested in the construction of the genome. Sequencing first successfully occurred with RNA, and later DNA. Biological samples like hair, skin scrapings, and blood can all be used. As long as a few cells are present, it's possible to extract their DNA and run it through a sequencer.

Medical researchers may perform gene sequencing to identify genetic abnormalities.
Medical researchers may perform gene sequencing to identify genetic abnormalities.

In DNA sequencing, the sample is tested to determine the order of the nucleotides. Researchers have been able to uncover specific genes that code for a variety of traits, from congenital heart conditions to brown hair. By looking at genetic variations across multiple individuals, researchers can identify the precise nucleotides used to code specific traits, and they can sometimes learn more about when the trait first appeared in the organism, and what kinds of factors can influence that trait.

Criminologists make use of DNA testing in their work to determine whether someone was present at a crime scene.
Criminologists make use of DNA testing in their work to determine whether someone was present at a crime scene.

Medical researchers are very interested in gene sequencing because the process can be used to identify genetic abnormalities. Researchers are also optimistic that the technique may someday lead to cures for specific conditions, along with additional general knowledge about the genomes of humans and other animals that could be useful. It's used today to test samples of material from fetuses to check for common genetic conditions and from parents who are concerned about passing down hereditary diseases.

Gene sequencing is a process in which the individual base nucleotides in an organism's DNA are identified.
Gene sequencing is a process in which the individual base nucleotides in an organism's DNA are identified.

In addition to being of interest to the medical field, gene sequencing interests scientists, because it allows them to set up a genetic clock to see when various traits emerged. This information can also be used to predict when an organism first appeared on Earth, and what it looked like at various points in its evolutionary lifetime. Criminologists also use DNA testing in their work, using common markers to test unknown samples against known DNA to see if someone was present at the scene of a crime.

Gene sequencing can be used to learn more about the genome of an organism.
Gene sequencing can be used to learn more about the genome of an organism.
Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Transgenic rats are used for the study of the gene function and gene regulation. And in the research of molecular biology, the sequence analysis of DNA is the basis of further research and modification of target genes.


I noticed that here it mentioned shotgun methods but not other methods like sanger or next generation sequencing. Why?


@TheGraham - Hey, I think I can answer that question about whether GenBank's information all comes from The Human Genome Project. Plain and simple answer: nope.

GenBank could only have gotten this enormous by letting people collaborate as much as they want. The database has some pretty rigorous quality control -- they'll closely examine every single thing before adding it to the database -- but they operate on submissions of data from individual labs in addition to the masses of information that gene sequencing centers provide.

I think GenBank is a cool idea, even if I don't really understand this gene sequencing stuff very well. The information is gibberish to me, but I'm sure it's like buried treasure to a scientist.


A few people on here are talking about GenBank, which I've read up on before, and I wanted to mention that even though the project is called "The Human Genome Project", it doesn't just map out human gene sequences.

The Human Genome Project has also mapped out DNA for animals that are commonly referenced for scientific experiments, like fruit flies and lab mice. Also, I'm not sure if the data is coming from the Human Genome Project, but GenBank houses hundreds of thousands of other sequences as well, including lots of microbes.

As of 2011, GenBank holds not only all of the gene mapping information that we have ever come up with for human DNA, but also the nucleotide sequences of over 300,000 other organisms, complete with supporting research notes from books and even annotations from the researchers. What an amazing wealth of scientific info right there!


@malmal - I don't know about every single gene sequencing process on the planet, but the Human Genome Project does have one big database where it stores the mapped DNA sequences.

The database is called GenBank, and it's the number one most referenced database for biological research anywhere in the world. It also offers free and open public domain access to the entire database to anybody who visits their web site -- very cool!

GenBank has been around since 1982, and has grown to literally over 61 million gene sequences over the years.

In case your question was about the literal "where", remember that we're dealing with the internet. Because computer databases don't actually have to all be in one spot thanks to the internet, the actual physical computers that store the database are located in the United States, in Japan, and in Europe, even though technically GenBank falls under United States government jurisdiction.

Hope this helps quell the curiosity a bit! If you're interested in this stuff, you should definitely look up Genbank -- reading about it is really fascinating.


@turkay1 - What you said about the Chinese mapping 10,000 microbes' DNA and whether they will share it with the rest of the world makes me really curious -- where do we store all of this mapped DNA work? I mean, is there any one big database for everyone?

I suppose it's too ideal to think that the various countries would have a database they all worked on together, but I could believe each country having some big database.

It seems to me like if there wasn't an official database of gene sequencing already established for this genome project, then people might not know what others have done before and start mapping DNA that has already been mapped by accident.

Is there a registry of some kind for which genes have been mapped, but everyone stores their own data in their own various databases, maybe? I'm super curious now.


Gene mapping is a revolutionary tool in numerous field, but I think one of the most practical uses for it is as a crime-fighting tool.

Using a DNA sequence, gene mapping is the technique that allows forensics experts to investigate a crime scene and test whose blood was found there, for example. In another situation, gene mapping might be used to test semen samples taken from a rape victim and then identify the attacker without a doubt instead of relying on more traditional testimony and evidence.

DNA mapping as a forensic tool was introduced in the mid 1980s, and at the time it was referred to as "DNA fingerprinting" because, like fingerprints, no two DNA samples are exactly the same.

Gene mapping has not only helped police investigators to catch the right criminal -- it has also finally proven innocent thousands of people who were wrongly jailed based on investigative evidence from before DNA forensics existed. Who says science doesn't affect our day to day lives?


Yea, other countries are doing gene sequencing as well. I think Japan, Canada, China are some of the big ones. But the most research by far is being done here in the U.S. In fact, it's not even comparable, U.S. probably has ten times more genetic sequencing projects than Japan. So we are definitely leading the world in this research.

National Institutes of Health funds most of our projects, followed by the Department of Energy. I think the Department of Agriculture is also funding some gene sequencing projects, although I don't know how much. I don't think that they fund remotely close to what the Department of Energy is funding though.


I read that gene sequencing is not just done on humans, it has been done on bacteria, animals, insects and plants as well. Some scientists actually believe that gene sequencing of bacteria and other microbes is even more important than human or animal genetic sequencing. I agree with that since many illnesses result from microbes, knowing their genetic sequence will prove useful in making new medicines to fight them.

I read about a huge project that is going on now on this. Surprisingly, it is not taking place in the U.S., but China. The Beijing Genomic Institute is working to sequence the genes of 10,000 microbes.

I really wish that a similar project was taking place in the U.S. Although I suppose that the Beijing Institute would share their findings with the rest of the world. I can see this project making waves in the medical world when it is completed and pharmaceutical companies will probably be first in line to get their hands on it.


I believe gene sequencing started out with the Human Genome Project in the early 90s. They not only found out the sequences of DNA but also created a database for it called the GenBank.

The great part about this database is that it is completely public. So any scientist that is doing work in this area can use it.

The reason that the sequencing has gotten so far and that we can now diagnose genetic diseases so early on is probably thanks to this database. I have hope that we will be able to prevent many of these diseases in the near future with gene sequencing.

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