I have two groups of RNA-seq data (A and B), with both two biological replicates within groups(A1, A2 and B1, B2). For each replicate, the reads are mapped two genomes(X,Y). Now i have counted the mapped reads for each orthologs between X and Y. Next, i want to do statistic test on expression ratio of X/Y between groups. I don't know which model or method could be used, anyone who can give suggestions. Thanks.