No Side Ef­fects

Economy of Belarus - - SCIENCE -

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.

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