Milk proteins of all mammals can be divided into two classes: the caseins and the whey proteins. The caseins (alpha-S1-casein, alpha-S2-casein, beta-casein, and kappa-casein) comprise the major protein component of ruminant milk and are secreted in the form of stable calcium phosphate micelles. The three calcium-sensitive genes, alpha-S1-casein, alpha-S2-casein, beta-casein, have evolved from a common ancestral gene by events such as gene duplication and exon shuffling whereas the k-casein gene appears to have evolved along a different pathway, since it does not share any common pattern with other casein genes. In the present study the relatedness of kappa- casein gene which is involved in milk clotting with fibrinogen gamma-chain , leucine rich repeat interacting protein 1 gene and chymosin gene involved in blood clotting, was being studied. The mammary derived kappa casein cDNA of Buffalo (Bubalus bubalis) was compared to the other three caseins along with fibrinogen γ chain , chymosin and leucine rich repeat interacting protein 1(LRRIP1) gene. kappa casein and chymosin are involved in milk clotting while fibrinogen γ chain and leucine rich repeat interacting protein 1 gene are involved in blood clotting. Phylogenetic analysis showed co-evolution of kappa casein gene with chymosin, fibrinogen γ chain and leucine rich repeat interacting protein 1 gene as their gene sequences culminated on one node while the other three caseins formed a different composite group. 1305537960.php