Figure 2 - Patterns of newly synthesized polypeptides present in the saliva of larvae through the end of the fourth instar. Larvae at different ages at the end of the fourth instar were injected with 1 Ál of [3H]-Leu solution. The secreted radioactive material was collected over a period of 2 h from 4 larvae and processed for SDS-PAGE and fluorography (Figure 2A). The ages of the larvae are indicated at the top of each lane. At age E5, the first DNA puffs begin to open and by E7+6h all are already closed, except DNA puff B10. The apparent molecular mass, in kDa, is assigned on the left side. Figure 2B presents a schematic diagram of the fluorogram in 2A. The relative quantities of the labelled polypeptides are indicated by the height of the bars. MM = Apparent molecular mass in kDa.