balal sadeghi - Department of Animal Science, and Research Institute of Biotechnology, Ferdowsi University of Mashhad, Mashhad, Iran
mohammadreza nassiri - Department of Animal Science, and Research Institute of Biotechnology, Ferdowsi University of Mashhad, Mashhad, Iran
Ali Masoudi-Nejad - Laboratory of System Biology and Bioinformatics, Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran
Mojtaba Tahmoorespour - Department of Animal Science, and Research Institute of Biotechnology, Ferdowsi University of Mashhad, Mashhad, Iran

MicroRNAs (miRNA) are a class of noncoding and regulatory RNA molecules about 22 nucleotides in length. MicroRNAs regulate gene expression by an RNA interfering pathway through cleavage or inhibition ofthe translation of target mRNA. Many miRNAs have been reported for their important roles in developmentalprocesses in various animals, but there is limited information about cattle and sheep miRNAs. The comparativegenomics approach due to their conserved nature is a good source for the miRNAs discovery. Cattle and sheep are ideal model organisms for biological and comparative genomics studies. In our study, a computational method based on expressed sequence tag (EST) analysis was used for detection of cattle and sheep miRNAs. Incattle, 25 miRNA candidates found by homology searching frequently clustered at certain chromosomes and 28 miRNAs in sheep had been detected. Our results show that the cattle and sheep miRNA database can be providing useful information for investigating biological functions of miRNAs in cattle and sheep. Furthermore, the bioinformatics approach is a good manner for studying these functions

microRNAs, comparative genomics, homology searching, sheep, cattle