The mean square projections of the end-to-end separation and radius of gyration along and perpendicular to the nematic director are determined for semiflexible polymer chains at the isotropic-nematic transition. The polymer chains are assumed to obey the Saito-Takahashi-Yunoki distribution for wormlike chains, interacting with each other through an Onsager-type excluded volume interaction, accurate to the second virial approximation.