investigation of kappa casein gene polymorphism by pcr-rflp in najdi cattle breed population in khuzestan province

more than 80% of the total milk protein contains caseins that are to forms α-s1, α-s2, β-casein and kappa casein. kappa casein is smaller than other milk proteins but due to have a role in size and stability of micelles. the present study describes polymorphism of kappa casein gene. this is the first study of kappa casein gene polymorphism in najdi cattle of iran. we used the polymerase chain reaction restriction fragment length polymorphism (pcr-rflp) technique to screen dna polymorphism in cattle. we amplified the 453 fragment consisting on part of exon 4. the amplified fragment was digested with hinfi restriction endonuclease and subjected to electrophoretic separation in 3% agarose gel. two alleles were observed, a and b. it gives frequencies of 0.54 and 0.46 for a and b alleles. also, genotypes aa, ab and bb with frequencies of 35%, 37.5% and 27.5% of the total study population were diagnosed. existence of hardy-weinberg equilibrium indicated that there was not any choice in order to increase or decrease the frequency of genotypes in the kappa-casein population in this herd. also, in this population kappa-casein gene has medium level of heterozygosity.