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Hearing loss is the most common sensory disorder and is genetically heterogeneous. Apart from nuclear gene mutations, a number of inherited mitochondrial mutations have also been implicated. The m.1555A>G mutation in the mitochondrial MT-RNR1 gene is reported as the most common mutation causing nonsyndromic hearing loss in various ethnic populations. We report here for the first time the clinical, genetic and molecular characterisation of a single large five-generational Tamil-speaking South Indian family with maternally inherited nonsyndromic postlingual hearing loss. Molecular analysis led to identification of m.1555A>G in 28 maternal relatives with variable degree of phenotypic expression. The penetrance of hearing loss among the maternal relatives in this family was 55%. Sequence analysis of the complete mitochondrial genome in 36 members of this pedigree identified 25 known variants and one novel variant co-transmitted along with m.1555A>G mutation. The mtDNA haplotype analysis revealed that the maternal relatives carry the R*T2 haplotype similar to Europeans and South Asians. Sequencing of the coding exon of GJB2 nuclear gene did not show any pathogenic mutations. The results suggest that other nuclear or environmental modifying factors could have played a role in the differential expression of mutation m.1555A>G in postlingual hearing loss in this family. [ABSTRACT FROM AUTHOR]

The article discusses the association of the risk of oral cancer with common mitochondrial polymorphisms and autosomal GSTP1 locus based on a study in India. The study screened polymorphisms at mitochondrial loci in patients with cancer and leukoplakia by polymerase chain reaction (PCR) restriction length polymorphism (RFLP). It found that the major alleles A at 12,308 nucleotide pair increased the risk of cancer in smokers but did not increase the risk of leukoplakia.

Water buffalo ( Bubalus bubalis) is broadly classified into river and swamp categories, but it remains disputed whether these two types were independently domesticated, or if they are the result of a single domestication event. In this study, we sequenced the mitochondrial D-loop region and cytochrome b gene of 217 and 80 buffalo respectively from eight breeds/locations in northern, north-western, central and southern India and compared our results with published Mediterranean and swamp buffalo sequences. Using these data, river and swamp buffalo were distinguished into two distinct clades. Based upon the existing knowledge of cytogenetic, ecological and phenotypic parameters, molecular data and present-day distribution of the river and swamp buffalo, we suggest that these two types were domesticated independently, and that classification of the river and swamp buffalo as two related subspecies is more appropriate. [ABSTRACT FROM AUTHOR]

The article examines the origin of the codon 47 (+A) b-thalassaemia mutation among the Nicobarese of the Andaman and Nicobar islands of India. Genetic studies based on mitochondrial DNA haplotypes were taken into account. Brief description and information about other findings and polymerase chain reaction is further presented.