A.R. Solimanifarjam, N. Asadzadeh, K. Khaledi, A. Javanmard, Detection of Polymorphisms in the Bovine Leptin (LEP) Gene: Association of a Single Nucleotide Polymorphism With Breeding Value of Milk Traits in Iranian Holstein Cattle, Journal of Molecular Genetics, Volume 2,Issue 1, 2010, Pages 10-14, ISSN 2070-4267, jmolgene.2010.10.14, (https://makhillpublications.co/view-article.php?doi=jmolgene.2010.10.14) Abstract: The objective of this study was to assess the association of polymorphism in leptin gene with breeding value of milk traits in Iranian Holstein cattle. Traits analyzed were breeding values of Milk and Fat production. A strategy employing polymerase chain reaction was used to amplify a 422 bp from blood, semen. Digestion of polymerase chain reaction products with Sau3AI revealed two alleles: Allele A was 390, 32 fragment and allele B was 303, 88 and 32 (only 303 fragment visible on the gel). Three patterns were observed frequencies were 0.900, 0.100 and 0.00 for AA, AB and BB, respectively (p≤0.21). The AB bulls were superior for milk fat production, in relation to homozygous AA. The Bovine leptin gene is strong candidates in the dairy cattle QTL search. This polymorphism could be further evaluated for marker assisted selection and the developed PCR methodology would expedite screening for large numbers of animal required for such studies. Keywords: polymorphism;holstein cattle;leptin;Milk traits;screening methodology;Iran