Distributions of Alu Subfamilies within the Genome andAlu-Containing Exons[i]
| Subfamily | Age (million years)[ii] | Distribution in the genome[iii] | Distribution in the set ofAlu-containing exons[iv] | ||||
| Occurrences | Percent | Occurrences | Percent | ||||
| Alumonomer | 112 | 1183 | 1% | 7 | 11% | ||
| Alu-J | 81 | 45156 | 29% | 26 | 43% | ||
| Alu-S | 48-31 | 88645 | 58% | 26 | 43% | ||
| Alu-Y | 19 | 15574 | 10% | 2 | 3% | ||
| Unknownfamily | — | 3087 | 2% | 0 | 0% | ||
[i] There is a statistically significant difference between two distributions (P < 6.4 × 10−21).
[ii] Age of Alu subfamilies from Kapitonov and Jurka (1996).
[iii] Distribution in the genome was calculated from a set of 153,645 human Alus compiled previously by Stenger et al. (2001), available at http://dir.niehs.nih.gov/ALU.
[iv] Subfamily types of the Alu sequences contained within alternatively spliced internal exons were determined usingRepeatMasker(http://repeatmasker.genome.washington.edu/cgi-bin/RepeatMasker).