# Global Repeat Map (GRM) Application: Finding All DNA Tandem Repeat Units
## 3 Results
### Comparison of Human, Chimp and Mouse Chromosome 19 GRM Results  
The GRM application found 3026 different arrays of TRs in human chromosome 19 (ReqSeq NC_000019.10), 2827 arrays of TRs in chimpanzee chromosome 19 (ReqSeq NC_036898.1) and 7316 arrays of TRs in mouse chromosome 19 (ReqSeq NC_000085.7). In total, in human chromosome 19 these TRs comprised 5,332,298 bp, in chimpanzee chromosome 19, 3,044,102 bp, and in mouse chromosome 19, 7,399,221 bp. Given that human, chimpanzee and mouse chromosome 19 have approximately the same number of nucleotides, it is obvious that the mouse genome has, on average, the most TR arrays.  
However, the distribution of repetitive DNA in these three organisms is significantly different (Figure 7). While in mouse chromosome 19 the largest number of repeats come from short TRs, in chimpanzee and human chromosome 19 a large proportion comes from medium-long and long TRs. This is largely due to ~171 bp alpha satellite DNA, which completely builds the centromeric and pericentromeric regions of chimpanzee and human genomes [61]. In addition, as we have shown in example three, in the centromeric region of human chromosome 19, parts of these alpha satellite monomers are organized into different inner HOR structures (Table 2, Figures 5 and 6).  
On the other hand, although the chimpanzee's centromeric region of chromosome 19 is also composed of ~171 bp alpha satellite monomers (TRs No. 1159-No. 1216 from Supplementary Table S2), it completely lacks organization into higher-order structures. Furthermore, mouse chromosome 19 has no alpha satellites at all, neither in the form of monomeric arrays, nor organized into HORs. In the mouse centromeric region, the GRM application finds only ~210 bp and ~384 bp TRs (Supplementary Table S3), which are organized in monomeric arrays without higher-order structures. These TRs are interesting examples of highly conserved, tandemly multiply repeated sequences in the centromeric and pericentromeric regions of the mouse genoma. Namely, it was found that there are two tandemly repeated sequences in the mouse genome, known as minor (MiSat) and major (MaSat) satellites, composed of 120-bp and 234-bp repeat units, respectively [62; 63]. However, it was shown that there are two levels of subunits within the 234-bp repeat unit (4 7-11 bp basic subunits form 28 bp/30 bp secondary  
Figure 6: Fragment diagram for part of centromeric region of human chromosome 19. Each dot in the Fragment diagram corresponds to the fragment length (component \(a_{3}^{i}\) of vector \(a^{i}\)) at that position (component \(a_{1}^{i}\) of vector \(a^{i}\)). On the left side of the diagram the alpha satellite monomers are organized in 17 mer HOR (2896: 171 \(\approx\) 17) structures, in the middle in 13 mer HOR (2216: 171 \(\approx\) 13) structures and on the left in tandem monomeric arrays without any HOR structures.  
subunits form 58 bp tertiary subunits and 458 bp/60 bp subunits form 234 bp quartic HOR units [63]. The differences between the human, chimpanzee and mouse TRs are due to their different evolutionary development (or possible sequence methods used for covering gaps in centromere sequence assembly).