Genome size estimation
Genome size of G. przewalski was estimated by using the K-mer method (Liu, et al. 2013) based on the Illumina X-ten next-generation sequencing data. As for the method, 17-mer was selected to do this analysis and the information of total k-mer and average k-mer depth was obtained from the quality-filtered reads. Finally, the genome size was obtained by calculation based on the formula: genome size = total k-mer number / average k-mer depth.