**3. Conclusions**

Genes and loci continue to be identified in aetiology of moderate to severe and progressive deafness. Current research has revealed that different alleles of a deafness gene can cause less severe hearing loss or more profound deafness. Further work needs to be carried out to identify additional loci and genes for progressive deafness and those for less severe hearing loss phenotypes as well as modifiers in the genetic background that suppress or enhance hearing loss. The contribution of different genes to moderate to severe and progressive hearing loss also needs to be studied in different world populations. Additionally, it remains important to document hearing loss in families which have already been described to suffer from moderate to severe hearing loss in order to check for progression of hearing loss in future. Strategies need to be evolved for identification of modifiers which will elucidate molecular pathways involved in normal hearing. This may be of help in designing strategies to treat and cure deafness in future.

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