(mentions CMT) Genetic Mapping Of Human Chromosome 1 Completed, Offering

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Genetic Mapping Of Human Chromosome 1 Completed, Offering Insights

Into Human Health (mentions CMT)

http://www.dukemednews.org/news/article.php?id=9661

DURHAM, N.C. -- A team of British and American scientists has

completed the detailed genetic mapping of human chromosome 1, the

largest single unit of genetic material in the human genome and the

final chromosome to be completely sequenced.

Researchers at the Wellcome Trust Sanger Institute and Duke

University Medical Center led the effort, which involved more than

150 scientists and took about 10 years to complete.

" This achievement effectively closes the book on an important volume

of the Human Genome Project, which was started in 1990 to identify

the genes and DNA sequences that provide a 'blueprint' for human

beings, " said Simon G. , Ph.D., assistant professor at the

Duke Center for Human Genetics and lead investigator on the study.

" Armed with this new information, researchers now have new tools for

probing fundamental biological questions and examining the genetic

factors involved in a range of diseases and medical conditions,

including Alzheimer's disease, Parkinson's disease, cancer, autism

and mental retardation, " said.

The researchers will publish their findings in the May 18 issue of

Nature. The study was funded by the Wellcome Trust and the Medical

Research Council in the United Kingdom, and the National Institutes

of Health in the United States.

The 23 human chromosomes -- the stringlike cellular structures that

contain genes and other DNA sequences -- are made up of millions of

chemical subunits called bases. The chromosomes are numbered from

largest to smallest. Chromosome 1 makes up about 8 percent of the

overall human genome, and it contains about twice as many genes as an

average-sized chromosome.

In their study, the researchers determined that chromosome 1 contains

3,141 genes, roughly a thousand of which had never before been

identified, said. Prior to joining the Duke Center for Human

Genetics in 2003, led the chromosome 1 project at the

Wellcome Trust Sanger Institute, which has sequenced more of the

human genome than any other institution.

Chromosome 1 plays a critical role in human health and well-being, he

said. Scientists have linked genetic mutations of the chromosome to

more than 350 human diseases, and structural alterations of the

chromosome are believed to contribute to a variety of mental

retardation syndromes.

" Given the key roles of chromosome 1, the completion of this project

has many exciting implications for the scientific and medical

communities, " said. " We are eager to apply this new wealth of

genetic information about the composition and structure of the

chromosome to important matters of health and disease. "

's colleagues at Duke already have used information from the

chromosome 1 sequence to identify genes associated with certain forms

of Charcot-Marie-Tooth disease, a neurological disorder that causes

loss of sensation to parts of the body.

In addition to mapping the chromosome's genes, the U.S.-U.K. team

also identified almost 4,500 new single nucleotide polymorphisms

(SNPs), or sections of DNA that vary slightly from the standard

sequence. In previous work, scientists have identified 15 SNPs that

influence the risk of developing diseases, including malaria,

said. However, the functions of the newly identified SNPs have yet to

be determined.

In another application, the new genetic map of chromosome 1 will help

scientists to better understand the processes that contribute to

genetic diversity among human populations, said.

The researchers found that the regions of the chromosome with the

highest concentrations of genes also have higher rates of

recombination -- " shuffling " of genetic material during reproduction -

- than other areas. By examining such shuffling, scientists are able

to gain a deeper understanding of the mechanisms that make us

genetically different from our parents, and from one another,

said. Loss or gain of certain regions of chromosome 1 during

reproduction and cell division also are factors in the development of

diseases and congenital conditions, and enhanced insight into these

processes may ultimately lead to better screening and treatment

options, he said.

Researchers already have used information from the HapMap Project, a

large international effort focused on investigating patterns in human

genetic variation, to look at variations in chromosome 1 among

population groups from Europe, West Africa and East Asia. The

researchers compared the prevalence of 68 SNPs in each of the groups

and noted differences among the populations, said. These

variations may provide clues to genetic distinctions among the

population groups and to the selection pressures each group has faced

through the centuries.

Researchers from the University of Washington-Seattle; the University

of Oxford; King's College London; University College London; and

Solexa Ltd. also participated in the chromosome sequencing project.