Figure 15: Comparison of L1 characteristics of autosomes and sex chromosomes as a function of (G+C) content in mouse (blue) and human (red).
From: Initial sequencing and comparative analysis of the mouse genome
Error bars depict standard deviation over all autosomes (circles). Diamonds, X chromosomes; squares, human Y chromosome. The mouse Y chromosome is not represented in the whole-genome assembly, and too little clone-based information is available to be included. a, The number of lineage-specific L1 copies per megabase declines 13- to 20-fold from lowest to highest (G+C) content. This relationship is stronger in mouse and on the sex chromosomes. Note that, for the same (G+C) content, L1 density is 1.5- to twofold higher on the sex chromosomes. b, The average length of lineage-specific L1 copies peaks at around the 39% (G+C) level, where it is three- (human) to fourfold (mouse) higher than in the (G+C)-richest regions. The average length in mouse is underestimated owing to the bias against full-length young elements in the shotgun assembly. On average, L1 copies are longer on human Y than on either X chromosome or the autosomes.
