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Shotgun sequencing

In shotgun sequencing many copies of the entire genome are "blown up" into millions of small fragments. Each small fragment is sequenced. Powerful computers then assemble the individual fragments into the original configuration. Repeat sequences pose a problem for this approach because their sizes can be much...

Small-molecule microarrays

Microarray technology is useful for screening many small molecules at once. DNA microarray can be used to measure the expression level of many genes simultaneously. DNA microarrays, for example, have been helpful in diagnosing different tumors. The widespread use of microarray technology promises to guide research...

Gel electrophoresis

In the early days of DNA manipulation, DNA fragments were laboriously separated by gravity. In the 1970s, the powerful tool of DNA gel electrophoresis was developed. This process uses electricity to separate DNA fragments by size as they migrate through a gel matrix. Gel electrophoresis can be used to...

Polymerase chain reaction (PCR)

Polymerase chain reaction (PCR) enables researchers to produce millions of copies of a specific DNA sequence in approximately two hours. This automated process bypasses the need to use bacteria for amplifying DNA.

This resource is part of the ...

Human genome sequencing

The public Human Genome Project started by identifying unique marker sequences distributed throughout the genome. Then, many copies of a small section of DNA were randomly cleaved into smaller fragments, and each small fragment was sequenced. Because there were originally many copies of the DNA in question, many...

Sanger method of DNA sequencing

Fred Sanger developed the first technique for sequencing DNA. DNA is replicated in the presence of chemically altered versions of the A, C, G, and T bases. These bases stop the replication process when they are incorporated into the growing strand of DNA, resulting in varying lengths of short DNA. These short DNA...

Making and running an agarose gel

A video guide for students illustrating the processes involved in running agarose gels in the laboratory.


Preparing the gel

Pouring the gel

Putting the gel into the gel tanks

Loading the samples

Running the gel

Visualising the nucleic acids


DNA sequencing - the Sanger method

In this method, the DNA is used as a template to generate a set of fragments that differ in length from each other by a single base. The fragments are then separated by size, and the bases at the end are identified, recreating the original sequence of the DNA.

This resource is part of the ...

Evolution of the Y chromosome

How did the human Y chromosome become so small relative to its X counterpart? This animation depicts the 300-million-year odyssey of the sex chromosomes that began when the proto X and Y were an identical pair.

Used with permission from the Howard Hughes Medical Institute, Copyright (2001).  All rights...

Damage to DNA leads to mutation

Reactive molecules, such as free radicals, and solar ultraviolet radiation can lead to mutations in DNA. Most mutations are corrected, but in rare cases mutations can accumulate and cause diseases such as cancer.

Used with permission from the Howard Hughes Medical Institute, Copyright (2003).  All rights...


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