Genetic variation in a species enhances the capability of organism to adapt to changing environment and is necessary for survival of the species. Genetic variation arises between individuals leading to differentiation at the level of population, species and higher order taxonomic groups. The genetic diversity data has varied application in research on evolution, conservation and management of natural resources and genetic improvement programmes, etc. Development of Molecular genetic markers has powerful ability to detect genetic studies of individuals, populations or species. These molecular markers combined with new statistical developments have revolutionized the analytical power, necessary to explore the genetic diversity. Molecular markers and their statistical analysis revolutionized the analytical power, necessary to explore the genetic diversity. Various molecular markers, protein or DNA (mt-DNA or nuclear DNA such as microsatellites, SNP or RAPD) are now being used in fisheries and aquaculture. These markers provide various scientific observations which have importance in aquaculture practice recently such as: 1) Species Identification 2) Genetic variation and population structure study in natural populations 3) Comparison between wild and hatchery populations 4) Assessment of demographic bottleneck in natural population 5) Propagation assisted rehabilitation programmes. In this review article, we have concentrated on the basics of molecular genetics, overview of commonly used markers and their application along with their limitations (major classes of markers) in fisheries and aquaculture studies

Forty-four primer sequences available for four cyprinid fishes were tested to amplify microsatellite loci in Indian major carp, Cirrhinus mrigala. A total of 12 loci were successfully amplified with clear scorable patterns and five thereof were polymorphic. Suitability of the identified polymorphic loci in population structure analysis of C. mrigala was assessed. Genetic variation was examined in 76 specimens collected from five different rivers. The mean observed heterozygosity ranged from 0.247 to 0.333. Significant heterogeneity in allele frequencies was detected, indicating that the samples analysed did not belong to homogenous populations. The identified microsatellite markers are promising for the analysis of intraspecific divergence in C. mrigala across its distribution range.

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This study was aimed to assess the association of Protein tyrosine phosphatase non-receptor22 (PTPN22) gene single nucleotide polymorphisms (SNPs) with rheumatic heart disease (RHD) susceptibility in 400 RHD patients and 300 controls. The PTPN22 polymorphisms (rs2476601, rs1217406 and rs3789609) were genotyped using Taqman probes (Applied Biosystems, Foster City, CA). Statistical analysis was performed by spss and haplotype analysis by snpstat. The frequencies of variant alleles were not different between controls and cases (rs2476601: 2.00% & 1.05%; rs1217406: 36.33% & 34.75%; and rs3789609: 38.17% & 40.00%, respectively]. However, G rs2476601 A rs1217406 T rs3789609 haplotype turned out to be a low risk factor for RHD (P = 0.0042) predisposition in females and adult patients. This study suggests PTPN22 haplotype may modulate the risk to RHD in North Indians.