The normal function of one tumor suppressor gene is to prevent cells with damaged chromosomes and DNA from “progressing from G1 to S,” whereas another tumor suppressor gene prevents “passage from G2...

The normal function of one tumor suppressor gene is to prevent cells with damaged chromosomes and DNA from “progressing from G1 to S,” whereas another tumor suppressor gene prevents “passage from G2 to M.” When these tumor suppressor genes fail to work, cancer can result. Explain what the phrases in quotations mean.