KISSING COUSINS MARRYING MORE RESEARCHERS: INBREEDING RISK NOT GREAT

                         Roanoke Times
                 Copyright (c) 1995, Landmark Communications, Inc.

DATE: MONDAY, February 15, 1993                   TAG: 9302150075
SECTION: NATIONAL/INTERNATIONAL                    PAGE: A6   EDITION: METRO 
SOURCE: The Los Angeles Times
DATELINE: BOSTON                                LENGTH: Medium
KISSING COUSINS MARRYING MORE RESEARCHERS: INBREEDING RISK NOT GREAT
Marriages between cousins and other close relatives are becoming more common in the United States and other Western countries as a result of immigration from countries where such marriages are accepted practice, scientists said here Sunday.
Several new studies suggest that the adverse genetic consequences of such inbreeding are real but are much less serious and widespread than is generally believed, researchers reported at a meeting of the American Association for the Advancement of Science. "There are ill effects, but they've probably been exaggerated in the past," said geneticist James V. Neel of the University of Michigan.
Such problems, he and other researchers said, are typically outweighed by the cultural and socioeconomic benefits of such unions.
These marriages, called consanguineous, are now prohibited in 30 states and carry heavy criminal penalties in nine. But the small increases in mortality resulting from them "don't warrant such heavy-handed legislation," said geneticist Alan Holland Bittles of the University of London.
"You can make a very good argument that inbreeding is not a bad thing," Neel said. "The problems are more sociological than biological."
Inbreeding is more common than many people suspect. An estimated 20 percent of marriages worldwide are between individuals who are first cousins or more closely related, with the incidence rising as high as 50 percent in countries such as Pakistan, Bittles said. In India, uncle-niece unions account for 20 percent of all marriages. And the number of consanguineous marriages is on the rise rather than declining, he added.
Such marriages play an integral part in the conservation of cultural values and property, he noted. "The question is not why there is so much inbreeding but why there isn't more," he said.
Inbreeding is not biologically hazardous in and of itself, but rather for the fact that it brings out the effect of deleterious genes that might have otherwise gone unnoticed. Of the estimated 100,000 genes in each human, scientists now believe that as many as 60 are defective. Most such defects are "recessive" - they don't produce any ill effects because the individual also inherited a good gene from the second parent.
But when two people with the same recessive gene mate, one of every four children will get two copies of the bad gene and develop the disorder. That disorder is often lethal early in life, but it can also cause such disabilities as congenital blindness, congenital deafness and lowered IQ, which do not threaten life.
The deaths of children with severe genetic defects, tragic as they may be, lead to the removal of bad genes from the gene pool, Neel said.
"Perhaps it's just nature cleaning up the genome."

by Archana Subramaniam by CNB