Table 1

Sequence repeat content for major interspersed repeat families

FamilyX chromosome Non-X chromosomes X vs. non-X Δ, %P value
bpNo.%bpNo.%
SINE5,420,45823,4059.5650,020,310220,53914.34−4.78<0.0001
Alu4,254,31915,8597.5141,809,635162,00111.99−4.48<0.0001
 MIR1,166,1397,5462.068,597,60358,5382.46−0.400.0008
LINE17,090,78919,68230.1659,450,470101,98917.0413.12<0.0001
 LINE-115,015,01313,01826.5046,839,14455,56513.4313.07<0.0001
 LINE-21,963,4316,3943.5612,761,31044,2333.66−0.100.3172
LTR5,090,8538,9418.9823,688,83648,9846.792.19<0.0001
 MaLRs2,247,8084,3153.9710,684,58725,1613.060.91<0.0001
 Retrovirus1,689,3162,5902.988,269,77813,8152.370.610.0010
 MER4961,2071,6921.693,930,7958,1811.130.56<0.0001
DNA1,411,0085,4832.498,515,50033,1762.440.050.2685
 MER1757,6403,6891.344,463,69521,6631.280.060.1140
 MER2499,0039950.883,217,4556,5100.92−0.040.2170
Mariner49,3941900.09210,6741,0570.060.030.01590
Total29,184,062NA51.50139,432,284NA39.9711.53<0.0001
 Total bp56,666,472348,844,905
  • Major classes for interspersed repeat content are shown in terms of the number (No.), total base pairs (bp), and percent bp (%) of repeats. LINE and LINE-1 content are dramatically increased on the X chromosome. The absolute difference (Δ) between mean X and non-X percentages was used to determine significance (Monte Carlo simulation; 10,000 replicates). A similar analysis has been performed addressing enrichment on the X chromosome in terms of G + C content (32). SINE, short interspersed element; MIR, mammalian-wide interspersed repeat; MaLR, mammalian LTR retrovirus; MER, medium reiteration frequency; NA, not applicable.