Fig. 4From: During evolution from the earliest tetrapoda, newly-recruited genes are increasingly paralogues of existing genes and distribute non-randomly among the chromosomesRegression of the content of (A) “young” genes (those assigned to phylostrata 15 through 19 or (B) “old” genes (those assigned to phylostrata 1 through 13) against the GC content of the chromosomes. The red-encircled points in both figures depict chromosome 5 while the blue-encircled points show chromosome 19Back to article page