Abstract :
LetKbe an algebraic function field in one variable over an algebraically closed field of positive characteristicp. We give an explicit upper bound for the number of rational points of genus-changing curves overKdefined byyp=r(x) and show that every genus-changing curve of absolute genus 0 has finitely manyK-rational points. We thus prove that every algebraic curve overKthat admits genus change under base-field extensions has finitely manyK-rational points.