DNA sequence variation in intron-1 of metallothionein gene in Zebu cattle exposed to toxic metals

Abstract

In the current study, an attempt was made to characterize partial intronic region of metallothionein (MT) gene in Zebu cattle residing within 5 km radius of thermal power plant and exposed for longer duration to toxic metals. PCR amplification and direct DNA sequencing of 396 bp intronic region was carried out for 36 animals from toxic metal exposed group and 5 animals from control group. The vast amount of DNA sequence data generated was analysed for detection of mutations among and between individuals of both groups. A total of 96 nucleotide substitutions were observed within control and exposed animals. Nucleotide substitution A-G was found at 10^th loci and the frequency of occurrence of A140G locus was 44%. Fourteen individuals indicated higher frequency of G-A nucleotide substitution while A-T nucleotide substitution was absent. While analysing various positions using chromatographs, it was found that at 137^th position, there was a presence of homozygous (GG) in control group sample and heterozygous (GA) in E21 & homozygous (AA) in E12 sample of toxic metal exposed group. The experimental population at all loci was not in Hardy-Weinberg equilibrium. It is necessary to screen other all structural and regulatory regions of this gene to find out DNA polymorphisms and relate them with indicator traits to explore metallothionein as marker for toxic metal homeostasis.