NEW YORK (Reuters Health) - Adding another volume to the growing library of genetic information, an international group of researchers released the full sequence of chromosome 14, the longest chromosome ever sequenced.

The newest human sequencing endeavor holds promise in the fights against numerous diseases, the authors note: chromosome 14 contains genes linked to crucial immune system function, as well as genes associated with more than 60 diseases. These diseases include early-onset Alzheimer's and other neurodegenerative problems.

Identifying the sequences of the genes that can lead to these devastating diseases may one day help treat them, according to study author Roland Heilig of the Genoscope-Center National de Sequencage in Evry, France.

Human cells generally contain 23 pairs of chromosomes, with each pair containing a chromosome from each parent. These structures carry the genes-a segment of DNA with a particular purpose--that contain the instructions for the body's development and function.

Heilig and his colleagues discovered that chromosome 14 contains 1,050 genes and gene fragments. The chromosome also appears to contain 393 non-active "pseudogenes."

In an interview with Reuters Health, Heilig said that he and his colleagues hope that the sequencing of chromosome 14 will prove "useful for the identification of genetic diseases."

Chromosome 14 carries genes linked to a number of conditions, including early-onset Alzheimer's disease, which can strike as early as the mid- to late-30s.

Other diseases with genes present on this chromosome are spastic paraplegia, neurodegenerative conditions marked by progressive weakness and stiffness in the legs, and Usher syndrome, which results in early hearing loss and gradual loss of vision.

Sequencing the abnormal forms of the genes that cause disease may one day lead to new treatments for those conditions. Heilig suggested that researchers could possibly mold new therapies around the proteins manufactured by abnormal genes. And although gene therapy techniques have had limited success, future endeavors may one day succeed in replacing an abnormal copy of a gene with a healthy copy, he noted.

"The sequence permits you to know the function of the gene, and maybe to discover some drugs that restore the protein for the gene," Heilig said.

Heilig noted that chromosome 14 is the 4th chromosome sequenced, and unlike previous sequences, the newest sequence is known in its entirety.

"The sequence is in one continuous piece, with no gap," Heilig said.

Other researchers involved in the sequencing hail from the Institute for Systems Biology in Seattle, Washington, and the Genome Sequencing Center at Washington University in St. Louis, Missouri.

SOURCE: Nature 2003;doi:10.1038/nature01348.