articles Chromosome Initial sequence contigs Sequence contigs Sequence. contig scaffolds Number N50 length (kb) Number N50 length (b) Number N50 length (b) 396913 87,757 23.048 23048.1 4,607 2.610 contigs in the genome sequance, the N50 length ranges from 1.7 to 5.5 times the arithmetic mean for initial sequence oontigs, 2.5 to 8.2 times for merged sequence contigs, and 6. 1 to 10 times for sequence-o Sequence gi basest(MD) Number Total bases Number Total Number in gaps (Mb) in gaps(Mb) in gaps°Mb) 145514 3.28 86.9 2,344 433 14 240 caffald (including gaps contained within clonesis 2.916G fingerprint done contigs that contain sequenced clones excluding gaps for centromeres. timate an average size of o 17 Mb per FCC gap, based on retrospective estimates of the clone coverage of chromosomes 21 and 22. Gap estimates for chror omosomes We estimate the average number of bases in sequence gaps from alignments of the initial sequence contigs of unfinished clones (see text and extrapolation to the whole chromosome. sizes of the sho overestimate, because the drat genome sequence contains some artefactual sequence owing to inability to correctly to merge al yielding a total estime heterochromatic regions and acrocentric short arm(s) NatuReVoL409115FebRuAry2001www.nature.comAe2001MacmillanMagazinesLtdarticles NATURE | VOL 409 | 15 FEBRUARY 2001 | www.nature.com 873 Table 7 Sequence level contiguity of the draft genome sequence Chromosome Initial sequence contigs Sequence contigs Sequence-contig scaffolds Number N50 length (kb) Number N50 length (kb) Number N50 length (kb) All 396,913 21.7 149,821 81.9 87,757 274.3 1 37,656 16.5 12,256 59.1 5,457 278.4 2 32,280 19.9 13,228 57.3 6,959 248.5 3 38,848 15.6 15,098 37.7 8,964 167.4 4 28,600 16.0 13,152 33.0 7,402 158.9 5 30,096 20.4 10,689 72.9 6,378 241.2 6 17,472 43.6 5,547 180.3 2,554 485.0 7 12,733 86.4 4,562 335.7 2,726 591.3 8 19,042 18.1 8,984 38.2 4,631 198.9 9 15,955 20.1 6,226 55.6 3,766 216.2 10 21,762 18.7 9,126 47.9 6,886 133.0 11 29,723 14.3 8,503 40.0 4,684 193.2 12 22,050 19.1 8,422 63.4 5,526 217.0 13 13,737 21.7 5,193 70.5 2,659 300.1 14 4,470 161.4 829 1,371.0 541 2,009.5 15 13,134 15.3 5,840 30.3 3,229 149.7 16 10,297 34.4 4,916 119.5 3,337 356.3 17 10,369 22.9 4,339 90.6 2,616 248.9 18 16,266 15.3 4,461 51.4 2,540 216.1 19 6,009 38.4 2,503 134.4 1,551 375.5 20 2,884 108.6 511 1,346.7 312 813.8 21 103 340.0 5 28,515.3 5 28,515.3 22 526 113.9 11 23,048.1 11 23,048.1 X 11,062 58.8 4,607 218.6 2,610 450.7 Y 557 154.3 140 1,388.6 106 1,439.7 UL 1,282 21.4 613 46.0 297 166.4 ................................................................................................................................................................................................................................................................................................................................................................... This Table is similar to Table 6 but shows the number and N50 length for various types of sequence contig (see Box 1). See legend to Table 6 concerning treatment of gaps. For sequence contigs in the draft genome sequence, the N50 length ranges from 1.7 to 5.5 times the arithmetic mean for initial sequence contigs, 2.5 to 8.2 times for merged sequence contigs, and 6.1 to 10 times for sequence-contig scaffolds. Table 8 Chromosome size estimates Chromosome* Sequenced bases² (Mb) FCC gaps³ SCC gapsk Sequence gaps# Heterochromatin and short arm adjustments**(Mb) Total estimated chromosome size (including artefactual duplication in draft genome sequence)²² (Mb) Previously estimated chromosome size³³ (Mb) Number Total bases in gaps§ (Mb) Number Total bases in gaps¶ (Mb) Number Total bases in gapsI (Mb) All 2,692.9 897 152.0 4,076 142.7 145,514 80.6 212 3,289 3,286 1 212.2 104 17.7 347 12.1 11,803 6.5 30 279 263 2 221.6 50 8.5 296 10.4 12,880 7.1 3 251 255 3 186.2 71 12.1 336 11.8 14,689 8.1 3 221 214 4 168.1 39 6.6 343 12.0 12,768 7.1 3 197 203 5 169.7 46 7.8 337 11.8 10,304 5.7 3 198 194 6 158.1 15 2.6 275 9.6 5,225 2.9 3 176 183 7 146.2 27 4.6 195 6.8 4,338 2.4 3 163 171 8 124.3 41 7.0 249 8.7 8,692 4.8 3 148 155 9 106.9 19 3.2 122 4.3 6,083 3.4 22 140 145 10 127.1 14 2.4 163 5.7 8,947 5.0 3 143 144 11 128.6 29 4.9 193 6.8 8,279 4.6 3 148 144 12 124.5 26 4.4 168 5.9 8,226 4.6 3 142 143 13 92.9 12 2.0 115 4.0 5,065 2.8 16 118 114 14 86.9 13 2.2 40 1.4 775 0.4 16 107 109 15 73.4 18 3.1 104 3.6 5,717 3.2 17 100 106 16 73.1 55 9.4 102 3.6 4,757 2.6 15 104 98 17 72.8 41 7.0 95 3.3 4,261 2.4 3 88 92 18 72.9 22 3.7 113 4.0 4,324 2.4 3 86 85 19 55.4 49 8.3 108 3.8 2,344 1.3 3 72 67 20 60.5 7 1.2 33 1.2 469 0.3 3 66 72 21 33.8 4 0.1 0 0.0 0 0.0 11 45 50 22 33.8 10 1.0 0 0.0 0 0.0 13 48 56 X 127.7 141 24.0 182 6.4 4,282 2.4 3 163 164 Y 21.8 6 1.0 19 0.7 113 0.1 27 51 59 NA 5.1 0 0 134 0.0 577 0.3 0 0 0 UL 9.3 38 0 7 0.0 566 0.3 0 0 0 ................................................................................................................................................................................................................................................................................................................................................................... * NA, sequenced clones that could not be associated with ®ngerprint clone contigs. UL, clone contigs that could not be reliably placed on a chromosome. ² Total number of bases in the draft genome sequence, excluding gaps. Total length of scaffold (including gaps contained within clones) is 2.916 Gb. ³ Gaps between those ®ngerprint clone contigs that contain sequenced clones excluding gaps for centromeres. § For un®nished chromosomes, we estimate an average size of 0.17 Mb per FCC gap, based on retrospective estimates of the clone coverage of chromosomes 21 and 22. Gap estimates for chromosomes 21 and 22 are taken from refs 93, 94. k Gaps between sequenced-clone contigs within a ®ngerprint clone contig. ¶ For un®nished chromosomes, we estimate sequenced clone gaps at 0.035 Mb each, based on evaluation of a sample of these gaps. # Gaps between two sequence contigs within a sequenced-clone contig. I We estimate the average number of bases in sequence gaps from alignments of the initial sequence contigs of un®nished clones (see text) and extrapolation to the whole chromosome. ** Including adjustments for estimates of the sizes of the short arms of the acrocentric chromosomes 13, 14, 15, 21 and 22 (ref. 105), estimates for the centromere and heterochromatic regions of chromosomes 1, 9 and 16 (refs 106, 107) and estimates of 3 Mb for the centromere and 24 Mb for telomeric heterochromatin for the Y chromosome108. ²² The sum of the ®ve lengths in the preceding columns. This is an overestimate, because the draft genome sequence contains some artefactual sequence owing to inability to correctly to merge all underlying sequence contigs. The total amount of artefactual duplication varies among chromosomes; the overall amount is estimated by computational analysis to be about 100 Mb, or about 3% of the total length given, yielding a total estimated size of about 3,200 Mb for the human genome. ³³ Including heterochromatic regions and acrocentric short arm(s)105. © 2001 Macmillan Magazines Ltd