Comparative idiogram analysis of the rat and the Yoshida rat sarcoma

17 Pags.- 3 Tabls.- 4 Figs.Complete idiogram analyses were made for ten spermatogonial metaphases of the rat and ten stemline metaphases of the Yoshida sarcoma. In Fig. 3 these analyses are summarized as two average idiograms. The evolution of the tumour idiogram cannot have taken place only by new combinations of unchanged chromosome arms. A great number of structural rearrangements, also involving smaller units, must be assumed. The morphologic identity within the originally homologous chromosome pairs has been totally blurred during the development of the tumour. The sex chromosomes of the rat have been followed during mitosis and meiosis. Both X and Y are heteropycnotic during the first meiotic division. only the Y shows heteropycnosis in spermatogonial mitoses; neither of them is clearly heteropycnotic in liver mitoses. The Y was identified as the smallest rod chromosome present. The X is one of the larger medium-sized rods, probably number five in size order counted from the longest rod.Peer reviewe