Figure 4.
Two marsupial X chromosomes compared with the human X. Green is recently added to the eutherian sex chromosomes. No marsupial sequence was available for RPS4Y or KDM5D, so we could not predict when the X–Y gametologues diverged from each other. The three shades of blue represent X genes that diverged from their respective gametologues either pre-therian radiation, post-therian radiation, or unknown. Genes retained from the proto-Y on the tammar wallaby and human Y chromosomes are shown. These results highlight the poor resolution of human X chromosome Stratum 1.
