Philadelphia - Deafness may be more common, according to a study presented here on October 6 at a meeting of the American society of Human Genetics. Researchers believe that increased opportunities for deaf people to meet and marry each other can lead to an increased frequency of an important class of deafness-causing mutations.
Gene mutations in over 0 locations on the genome because of inherited deafness, which represents about half of deafness in general. Recently, clinical geneticists reported that defective copies of a gene called Cx 26 cause about 35% of all cases of deafness.
This number seemed remarkably high at Walter Nance, a geneticist at Virginia Commonwealth University in Richmond. From a statistical analysis of data on American families of the 19th century with deaf children, it considered that, in those days, Cx 26 mutations accounted for only 17% of hereditary deafness. Nance said that intermarriage could explain the increase of 26 Cx deafness, because both parents with this mutation will always have deaf children. Marriages between deaf have been on the rise since the development of sign language and the establishment of schools for the deaf in the last 2 centuries.
To test this theory, Nance traveled to Mongolia, where marriage between deaf is still relatively rare. There he collected the DNA of about 100 deaf and hearing 150 people. As he suspected, very few deaf Mongolians had mutations in Cx 26.
Not everyone is convinced. "It is a reasonable assumption, because deaf people tend to marry Deaf" said David Kelsell, a geneticist at Queen Mary and Westfield College in London, UK. But he says Nance needs to repeat the study in other ethnic populations, because the frequency of mutations Cx 26 may have been different in Mongolian to start. Nance accepts; his lab has already started to examine the frequency of Cx 26 mutations in Turkey.
If his theory is correct, Nance said, it would mean that mixed marriages are not only to increase the percentage of deafness due to Cx 26, but also the prevalence of deafness. So far, it has been difficult to measure because there are no good data on the occurrence of deafness in the past.
Related Sites
summary of Nance in the meeting of the American Society of Human Genetics
homepage Connexin deafness
hereditary hearing loss homepage
National Institute on deafness and other communication disorders
0 Komentar