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Table 2 Base composition (in percent GC) of introns and at the third position of four-fold degenerate amino acids.

From: Codon usage in twelve species of Drosophila

  Dmel Dsim Dsec Dyak Dere Dana Dpse Dper Dwil Dmoj Dvir Dgri
All 6,698 homologues             
No. introns 24960 19890 20742 20768 20716 20826 20492 20467 20535 20784 20772 20876
Total intron length (Mb) 27.9 12.0 12.2 13.3 12.8 14.4 12.7 13.4 18.2 17.0 16.5 15.4
Average intron length (bp) 1119 1546 1520 1637 1582 1991 2075 2107 2565 2236 2120 1754
No. introns: 100/2000a 8769 4505 4606 4700 4698 4227 3460 3509 3860 4472 4769 5324
Intron GC% (Wt.)b 40.3 41.1 41.0 40.8 41.4 40.8 44.1 44.3 35.1 37.3 38.6 36.8
Intron GC% (Ave.)c 37.0 38.5 38.2 37.7 38.6 38.2 43.3 43.9 34.2 35.5 37.3 33.7
Intron GC% (Ave. 100/2000)d 37.6 37.9 37.5 37.2 37.9 37.5 42.5 43.0 33.5 34.5 36.5 32.7
GC% 4-fold AAe 66.8 68.3 67.9 68.1 68.4 65.8 69.7 69.5 51.0 64.2 66.3 62.8
33 F homologues             
Intron GC% (Wt.)b 32.1 (31.3)f 34.0 32.3 33.3 32.6 39.4 35.4 35.9 35.8 35.8 34.2 30.2
Intron GC% (Ave.)c 28.8 (28.4)f 29.0 28.3 28.5 27.9 28.8 31.3 31.1 34.1 31.2 30.6 26.9
Intron GC% (Ave 100/2000)d 29.8 (29.8)f 32.7 31.4 32.0 30.5 30.6 33.8 34.2 33.3 33.9 32.9 26.5
GC% 4-fold AAe 37.9 37.8 37.5 37.5 37.5 34.7 43.7 43.3 44.9 43.4 50.8 53.4
  1. aSubset of introns between 100 and 2000 bp after removing 50 bp at each end and possible transposable elements.
  2. bWeighted average %GC from cumulative sequence (all introns concatenated).
  3. cUnweighted average %GC from all introns.
  4. d Unweighted average %GC only from introns between 100 and 2000 bp after removing 50 bp at each end and transposable elements.
  5. eGC% of third position of four-fold degenerate amino acid codons.
  6. fGC% from all 79 genes known to be on the F element in Dmel that have introns are shown in parentheses.