Bioscience Methods 2025, Vol.16, No.4, 183-192 http://bioscipublisher.com/index.php/bm 189 Figure 3 The direct DNA sequence comparison between C. angulata and C. gigas genomes. (A) The dot plot for the comparison of the 10 pairs of pseudo-chromosome sequences. Top x-axis: G1-G10, the pseudo-chromosomes (10 largest scaffolds: cgiscf1-cgiscf10) in the C. gigas genome. Right y-axis: A1-A10, the pseudo-chromosomes (10 largest scaffolds: canscf1-canscf10) in the C. angulata genome. Bottom x-axis: the length of G1-G10. Left y-axis: the length of A1-A10. The sequence identities were represented by the upper right colors. (B) The synteny of conserved DNA blocks between the two genomes. The two images were drawn from DNA blocks with a size of ≥1 000 bp and ≥10 000 bp (max=226 631 bp), respectively. (C) The distribution of alignment identities of the conserved DNA blocks in the 10 pairs of pseudo-chromosomes. x-axis: sequence alignment identity. y-axis: the 10 pseudo-chromosome pairs. The black vertical lines in the bean plot denote the median values. ide1: the alignment identity measured by the gap-uncompressed method. ide2: the alignment identity measured by the gap-compressed method. (D) A sketch map for the large indels in the alignments of conserved DNA segments. The four DNA alignments are from A3:13,369,498-13,506,783 vs G3:12,755,799-12,900,025, A5:4,508,362-4,563,006 vs G5:5,295,108-5,404,622, A6:20,475,358-20,598,634 vs G6:21,302,015-21,412,762, and A7:6,838,813-6,932,940 vs G7:7,304,889-7,382,157, respectively (Adopted from Qi et al., 2022) 7 Conclusion Not all species have their origins as clear as in books, but in the case of oysters, at least now there is a much clearer picture than before. Judging from current genetic data and fossil records, they probably appeared near the Arctic in the early Jurassic period. Later, with the opening of the Atlantic Ocean and the changes in the Tethys Ocean, the species and number gradually increased. But things are not that simple. What you see is a group of shells that look similar, but what the genes tell us is a very clear lineage. That's how those hidden species that "can't be seen but are really different" were discovered. In addition, they are particularly sensitive to
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