**3.3.** *Xiphophorus* **genome sequencing and assembly**

Sequencing of *X. maculatus* genome is of great value to the aquatic model community [3, 21]. A problem encountered by those using the *Xiphophorus* model was that a genome sequence of one single *Xiphophorus* parent used in an interspecies cross did not allow the regulation of allele-specific gene expression to be determined in interspecies hybrid. The interspecies crosses are important in disease model research for both spontaneous and induced melanoma and other life history traits that involve complex genetic interactions. Therefore, 2 additional *Xiphophorus* species genomes (*X. couchianus* and *X. hellerii)* have been sequenced and assem‐ bled. In this section, sequencing and assembling multiple *Xiphophorus* species genomes is used as real-world example of the process of genome sequencing.
