Individual, family gene studies help locate causes of inherited diseases

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Individual, family gene studies help locate causes of inherited diseases

Wed Mar 10, 8:10 PM

By Randolph E. Schmid, The Associated Press

WASHINGTON - Children inherit about 30 changed genes from each parent, fewer

than had been thought, according to a first detailed look at the blueprint for

human life in a family.

Yet that was enough to pass on an inherited illnesses in that family. And a

separate study of an individual genome located the cause of another inherited

disease.

That blueprint for life, called DNA, contains about 22,000 genes and researchers

calculated the number of changes by analyzing the genes of a mother, father and

their son and daughter.

The result, reported in Thursday's online edition of the journal Science, found

that the children had about 30 mutations from each parent for a total of 60

changes passed along to the offspring.

Scientists had previously thought a child had about 75 mutated genes from the

parents.

The rate probably will vary somewhat, depending on the age of the parents, said

co-author Lynn B. Jorde, chairman of the Department of Human Genetics at the

University of Utah School of Medicine.

Most mutations are thought to be unimportant, but the rate at which things

change is considered critical, helping explain the gradual development of

changes.

Jorde and the senior author J. Galas of the Institute of Systems Biology

in Seattle, Washington, studied a family in which the parents had no genetic

abnormalities, but each carried recessive genes that resulted in their son and

daughter being born with two extremely rare conditions - 's syndrome and

primary ciliary dyskinesia.

's syndrome, which causes facial and limb malformations, has been

diagnosed in only two families in the world. PCD is a condition in which the

tiny hair-like structures that are supposed to move mucus out of airways in the

lungs do not function. The chances of having PCD are estimated at one in 10,000.

Jorde said the odds of someone having both PCD and 's syndrome are less

than one in 10 billion.

" We were very pleased and a little surprised at how much additional information

can come from examining the full genomes of the same family, " Galas said in a

statement.

" Comparing the sequences of unrelated individuals is useful, but for a family

the results are more accurate. We can now see all the genetic variations,

including rare ones, and can construct the inheritance of every piece of the

chromosomes, which is critical to understanding the traits important to health

and disease, " he said.

The family was not named in the report.

Meanwhile, a separate report in the New England Journal of Medicine disclosed

that Dr. Lupski of Baylor College of Medicine in Texas had sequenced his

own complete genome and identified the gene involved in his form of

Charcot-Marie-Tooth syndrome, which affects the function of nerves in the body's

limbs, hands and feet.

Lupski, vice chairman of molecular and human genetics, said the work

" demonstrates that the technology is robust enough that we can find disease

genes by determining the whole genome sequence. We can start to use this

technology to interpret the clinical information in the context of the sequence

- of the hand of cards you have been dealt. "

" Isn't that the goal or dream of personalized genomic medicine? " he said in a

statement.

Lupski said he has known for 40 years that he had a disease caused by recessive

genes. Now he knows the gene at fault.

And Lupski and colleagues found that having a single copy of the recessive

mutation is susceptible to carpal tunnel syndrome, which usually affects people

who perform repetitive motions that compress a nerve where it crosses the wrist.

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On the Net:

Science: http://www.sciencemag.org

New England Journal of Medicine: http://www.nejm.org