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researchers took samples from over 500 hearing-impaired children aged from 2 to 17 years from Minsk, Pinsk, Gomel, Grodno, Vitebsk and Bobruisk. Scientists studied their DNA and performed molecular genetic analysis. They found over ten mutations in nuclear DNA and several mutations in mitochondrial DNA that cause hearing impairments and deafness.
The scientists revealed that more than half of hearing-impaired children in Belarus have mutated gene GJB2. This mutation can cause congenital deafness in one in sixteen Belarusians. This mutation is most common in Western Polesye where it was diagnosed in every tenth resident. The prevalence of this mutation is rather high in Belarus (6%) when compared with other countries, like Greece and Italy (3%), or Estonia (4.5%).
Hearing loss is not a rare disease among Belarusians. The most frequent cause is mutations in the GJB2 gene. Mom and dad often carry this defective gene while they suffer no hearing problems themselves. If a child inherits two copies of the mutated gene, one from each parent, he is destined to be deaf, said Nina Danilenko, Doctor of Sciences (Biology), Associate Professor, Senior Researcher at the Institute of Genetics and Cytology at NASB.
Such defective allele is a historical mutation. It is more than 10,000 years old. Initially it spread throughout Europe, and then spilled over into other parts of the world. There is a perception that carriers of this genetic defect have some physiological advantages that compensate for the defective gene. For example, they have a thicker skin, and thus they suffer less from bites of blood insects that spread various infectious diseases. Perhaps this is the reason why this mutation has not been eliminated in the process of natural selection.