Diagnosing and Treating Genetic Diseases
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The Human Genome Project (HGP) was launched in the 1980s as an organized effort to provide the information researchers need to understand the genetic basis of all disease. A genome is all the genetic information that makes an organism. The HGP, completed in April 2003, mapped the location of each of the genes in the human genome and sequenced--decoded--each gene's instruction. The project was overseen by both the NIH and the Department of Energy.

Courtesy of the National Human Genome Research Institute.

The HGP is like translating an entire library of books written in a foreign language -- the genetic code. But with the "library’s" information, researchers can investigate just what each gene is responsible for in the human body, and how mutations to genes cause genetic diseases. This information may help researchers develop tests and treatments for genetic diseases, which will reduce human suffering and add productive years to our lives.

To study genes, researchers use a convenient way to make many copies of a DNA strand. They call the method "polymerase chain reaction", known as PCR. PCR quickly multiplies DNA segments in a test tube. Almost every researcher in this exhibit used PCR.
 
Scientist looking at DNA sequencing gel. Courtesy of the National Cancer Institute.

In PCR, researchers select which genes they are interested in and use heat to separate the DNA strands that encode that gene. Then, on each end of a separated strand, primers (short strings of nucleotides) bind to the DNA sequences which complement them. Nucleotides fill in the middle to form a second complete DNA strand. Repeating these steps on all of the copies creates a billion copies of the target DNA in a few hours.

How PCR works.
Courtesy of the National Human Genome Research Institute


A method that researchers use to study genes and chromosomes is called "fluorescence in situ hybridization" (FISH). This long name describes a process which binds chemicals that are fluorescent (they glow when exposed to a certain light) to DNA segments whose genes are known. Then researchers can see where the genes fit in the chromosome. By using many colors of fluorescent chemicals, a researcher can "paint" the genes of a whole chromosome. Once a researcher knows where a certain gene is supposed to be on a chromosome, s/he can use FISH to see if the gene is located in the wrong place on the chromosome or is on a different chromosome altogether. Genes that are in the wrong location may cause a genetic disease.
  Fish Result
Courtesy of the National Human Genome Research Institute
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Revolution in Progress: Human Genetics and Medical Research/
National Institutes of Health