Figure 1

Quality and amount of total RNA preparations from imaginal discs. Total RNA was prepared separately from 2, 4 and 12 third-instar larval wing imaginal discs using the Mini RNA Isolation Kit (Zymo Research). The total amount of RNA, based on the absorbance at 260 nm (A₂₆₀), was 462, 540 and 1,530 ng, respectively. The A₂₆₀/A₂₈₀ ratios of 2.08, 2.2 and 2.27 for the separate preparations is indicative of high-quality RNA preparations. The amount of total RNA per disc was calculated to be 230, 140 and 130 ng, respectively. Assuming a poly(A)⁺ RNA content of 1-2%, this amount of total RNA roughly corresponds to 1-4 ng poly(A)⁺ RNA per wing disc (62,000 cells). The other discs are smaller and contain fewer cells. The equivalent of 1, 2 and 6 discs was separated on a denaturing agarose gel (lanes 1, 2 and 3, respectively). The two prominent bands represent the 18S and 28S ribosomal RNA populations (arrowheads). Poly(A)⁺ RNA is detected as a smear. No obvious small-molecular-weight products were observed. Lane M contains molecular-weight markers, with numbers indicating the approximate lengths in nucleotides.