The proximal portion of Chlamydomonas flagella contains a distinct set of inner dynein arms.

A specific type of inner dynein arm is located primarily or exclusively in the proximal portion of Chlamydomonas flagella. This dynein is absent from flagella less than 6 microns long, is assembled during the second half of flagellar regeneration time and is resistant to extraction under conditions causing complete solubilization of two inner arm heavy chains and partial solubilization of three other heavy chains. This and other evidence described in this report suggest that the inner arm row is composed of five distinct types of dynein arms. Therefore, the units of three inner arms that repeat every 96 nm along the axoneme are composed of different dyneins in the proximal and distal portions of flagella.