The Origin and Behaviour of Chiasmata
XI. Dasyurus and Sarcophilus
1936 年 7 巻 1-2 号 p. 82-103
詳細
1936 年 7 巻 1-2 号 p. 82-103
1. Dasyurus and Sarcophilus have six pairs of autosome chromosomes. In Sarcophilus they show slight variation in length; in Dasyurus this is greater. The loci of attachment constrictions are median, submedian or subterminal.
2. The ehromosomes exhibit somatic pairing at mitotic metaphase.
3. The contraction of prophase chromosomes at mitosis is less in Sarcophilus than in Dasyurus, and the time required to arrive at the metaphase stage is longer.
4. At meiotic prophase the chromosomes contain well defined chromomeres. The number of varying sizes of chromomeres is the same in homologous chromosomes.
5. The zygotene and pachytene stages are very long. The pairing of homologous ehromosomes begins in one of the terminal regions, and never more than two separate segments of the same chromosome are involved.
6. At the end of pachytene a sudden change takes place in the first spermatocyte; the chromosomes loose their staining capacity and the volume of nuclei and Gell inereases. It is suggested that this stage is equivalent to the resting stage in that the delayed splitting of chromosomes occurs.
7. In Dasyurus there is a high chiasma interference with lower chiasma frequency than in Sarcophilus.
8. The relationship between the length of chromosomes and the chiasma frequency is disproportionate in Dasyurus, but is independent in Sarcophilus.
9. The different types of pachytene interlocking are described. One Gase is illustrated where interlocking leads to segmental interchange.
10. Chiasma frequency in multinucleate spermatocytes shows slight variation within the saure cell, which variation must be genetic.
