By comparing mouse fibroblasts from two parental strains (Bl6 and Spretus) with fibroblasts from their first generation offspring (F1) we can detect allele specific expression of proteins. The Bl6 and Spretus lines are evolutionary distant and harbour many SNPs in their genomes which when synonomous we can detect on the protein level using mass spectrometry. By mixing SILAC labeled Bl6, Spretus and F1 offspring cell lines we can detect peptides shared between all three cell lines and also SNP peptides that are only expressed in the F1 cells and either Bl6 or Spretus cells. By comparing the abundance of the shared peptides and the SNP peptides we can quantify how much of a protein in the F1 cells that comes from the paternal or maternal allele. This data were then further compared to polysome profiling data. Azidohomoalanine labeling was used to enrich newly synthesized proteins from the three cell lines.