During long-zero regeneration, there is a linear correlation between IFT train size and flagellar length. (A) Three examples of KAP-GFP cells undergoing long-zero regeneration, showing brighter IFT trains in the shorter of the two flagella (cell dimensions are diagramed above the kymographs). As the length disparity between the long and short flagella increases (kymographs left to right), the difference in average train intensity also increases. Kymographs were generated from Videos 3–5. (B) Example of an IFT27-GFP long-zero cell. Kymograph was generated from Video 6. (A and B) Bars: (horizontal) 5 µm; (vertical) 1 s. (C) Plotting data from all of the KAP-GFP and IFT27-GFP long-zero cells together reveals a linear relationship (r² = 0.86) between the ratio of flagellar lengths and the ratio of IFT train intensities. Train intensities were corrected for the flagellar background and normalized by the ratio of integrated flagellar intensities (Fig. S3 B) to control for variability in total IFT content. (D and E) Despite this correlation between length and train intensity, the speed (D) and frequency (E) of IFT is the same in both the long and short flagella. (C–E) Data are plotted on a ratio scale. S, short flagella; L, long flagella, C, corrected for camera noise; F, corrected for flagellar background.