Figure 3.
Percent L1 vs. percent G + C composition. Nonoverlapping genomic sequences from the X chromosome (a) and chromosome 7 (b) were binned into cytogenetic band intervals based on cytogenetic and radiation hybrid mapping data (http://www.ncbi.nlm.nih.gov/genome/seq/). The percentage L1 content and G + C content for each bin of sequence is depicted graphically. Since the precise boundaries of cytogenetic bands are not known at the sequence level, many of the bins bracket two or more cytogenetic band intervals. L1s have been separated into old (L1M4 to L1M2) and young (L1M1, L1P5 to L1P1, L1Hs). The clustering of younger L1s at Xq13 and Xq21 suggests both a temporal and a positional bias in the accumulation of L1s on the X chromosome. The linear correlation (r2) between G + C and L1 content was 0.24 for the X chromosome and 0.50 for chromosome 7.