xvii, 125 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / MicroRNAs are small regulatory RNAs that control various developmental and physiological processes in animals and plants. To study the involvement of microRNAs in skeletal development, I manipulated the expression of miR-140, which is strongly expressed in the developing skeleton, and miR-196, which is located among the body patterning Hox cluster genes. I found that miR-140 regulates zebrafish palate formation by interfering with neural crest cell migration through the inhibition of the expression of the platelet derived growth factor receptor alpha ( pdgfra ) gene. I also found that miR196 regulates zebrafish pectoral fin initiation by regulating the expression of the retinoic acid receptor alpha b ( rarab ) gene and that miR-196 is involved in the patterning of zebrafish pharyngeal arches and vertebrae. These results illuminate previously unknown regulatory mechanisms of skeletal development. I also reviewed current knowledge concerning microRNAs in skeletal development and evolution and discussed potential relationships between microRNAs and skeletal disease. This dissertation includes previously published and unpublished coauthored material. / Committee in charge: Judith Eisen, Chairperson, Biology; John Postlethwait, Advisor, Biology; Charles Kimmel, Member, Biology; William Cresko, Member, Biology; J. Andrew Berglund, Outside Member, Chemistry