The homologous chromosome pairs in our cells do not carry identical sequences in all loci. This heterozygosity (difference between the two copies) can be altered in cancer: in fact, loss of heterozygosity at many loci is observed in cancer cells, through an increase in either homozygosity (two identical copies) or hemizygosity (i.e. loss of one copy). Researchers can take advantage of this loss of heterozygosity in cancer cells to identify genomic loci that contain cancer-critical genes. What type of gene would you expect to find in chromosomal regions with a loss of heterozygosity? Proto-oncogenes (P) or tumor suppressor genes (T)? Write down P or T as your answer.