Question: What is the detectable marker used for selection of the modified organism? Need Assignment Help? To identify the origin of TSE-04, we referred to a similar previous study (Sun Zhaodi et al., 2023). The 18S rRNA of TSE-04 was amplified by PCR for species identification. As shown in Fig. 5A, PCR analysis revealed the expected 1841 bp fragment of 18S rRNA, which closely matched the 18S rRNA sequences of O. niloticus downloaded from (GenBank accession XR_003216134.1). The amplified fragments were then sequenced and compared to the known 18S rRNA of O. niloticus, confirming that TSE-04 was derived from this species. Furthermore, TSE-04 exhibited a robust expression of Cytoskeletal 8, an epithelial cell- specific marker, at both the gene (Fig. 5A) and protein level (Fig. 5B), confirming their epithelial characteristics.