Single Gene Disorder or Mendelian disorder are those when a distinct phenotype is attributed to a single gene. There are many such Human Genetic Disorders which have been reported and the number is growing exponentially. These disorders follow very deducable inheritence pattern like autosomal dominant, atuosomal recessive and sex linked, which can be traced by pedigree analysis. In some disorders like haemophilia, phenylketonueria, huntington, muscular distrophy, thallessemia, etc. with high frequency of occurrence in population mutation are also enlisted. In such cases basic PCR based or RT-PCR based analysis provides a valuable information. Yet in some cases complete exon or gene sequencing is needed to be undertaken, to undermine the responsible mutation.