African clawed frog
After becoming a faculty member in zoology in the University of Texas at Austin, Jeffery published a study in "Developmental Biology" which suggested that Poly(A)-binding protein is present in oocyte and is responsible for oogenesis in the African clawed frog. In 1983 he along with Craig R. Tomlinson and Richard D. Brodeur studied "Styela plicata"'s eggs and suggested that cytoplasmic regions also carry messenger RNA codes for actin isoform. In 1995 he, Billie J. Swalla and Noriyuki Satoh studied tailless tadpole larvae of the Ascidiacea species and discovered that the Manx gene may be responsible for tail control and development.