GERM CELLS, WHICH EVENTUALLY DEVELOP INTO EGGS OR SPERM, CARRY THE GENETIC INFORMATION OF AN INDIVIDUAL FROM ONE GENERATION TO THE NEXT. THESE CELLS ARE SET ASIDE DURING THE EARLY DEVELOPMENT OF THE EMBRYO, BUT WE DO NOT KNOW HOW, WHEN, OR WHERE THIS HAPPENS IN CATTLE. GERM CELLS ARE CRITICAL TO AN ANIMAL'S FERTILITY, AND BETTER UNDERSTANDING HOW THEY DEVELOP CAN OPEN THE DOOR TO NEW APPROACHES FOR GENETIC IMPROVEMENT OF LIVESTOCK. ENHANCED FERTILITY AND GENETIC QUALITY ARE BOTH MAJOR FACTORS THAT COULD INCREASE THE EFFICIENCY OF LIVESTOCK OPERATIONS IN THE FACE OF GROWING DEMAND FOR ANIMAL PRODUCTS AND NEED FOR SUSTAINABLE SYSTEMS. IN THIS PROJECT, I PROPOSE TO ESTABLISH THE TIMING, LOCATION, AND SPECIFIC CHARACTERISTICS THAT SET THE EARLIEST GERM CELLS, KNOWN AS PRIMORDIAL GERM CELLS (PGCS), APART FROM OTHER CELLS IN THE BOVINE EMBRYO. THE FIRST AIM IS TO IDENTIFY THE PRESENCE AND REGION OF THE FIRST BOVINE PGCS BY LABELING EMBRYOS AT DAY 12-18 OF PREGNANCY WITH ESTABLISHED MARKERS OF EARLY GERM CELLS. THE SECOND AIM WILL FOCUS ON CHARACTERIZING THE IDENTITY OF NEWLY-FORMED BOVINE PGCS THROUGH ANALYSIS OF THE GENE EXPRESSION PROFILES OF THE INDIVIDUAL CELL POPULATIONS OF THE EMBRYO BY A TECHNIQUE CALLED SINGLE-CELL RNA-SEQUENCING. THIS WILL REVEAL WHAT MAKES GERM CELLS UNIQUE FROM THE OTHER CELLS OF THE EMBRYO, AND WILL PROVIDE DETAILS TO ALLOW PGCS TO BE ISOLATED FROM OTHER CELL TYPES FOR FUTURE STUDIES. ONCE COMPLETED, THESE AIMS WILL PROVIDE THE FOUNDATION FOR FURTHER EFFORTS TO DEVISE METHODS TO IMPROVE THE CURRENT TECHNOLOGIES FOR ASSISTED REPRODUCTION AND ULTIMATELY THE EFFICIENCY AND SUSTAINABILITY OF PRODUCTION OF LIVESTOCK ANIMALS.