Abstract
The morphology, G- and C-banding pattern of the Akodon mollis chromosome complement is analysed. Over a total of 14 males and 10 females studied, 8 males and 7 females had a modal chromosome number of 22, while 6 males and 3 females showed a modal number of 23 chromosomes. In the animals with 23 chromosomes the odd element was considered a B chromosome on the basis of: (a) its small size, (b) the lack of an homologous chromosome and the subsequent formation of univalents at diakinesis and metaphase I from testes, (c) the weak or null genetic action as evidenced by the lack of any obvious variation in the phenotype of carriers.
Four females exhibited a sex-pair dimorphism indistinguishable from that observed in males. The G-banding analysis showed homology between the pattern found in the Y chromosome and that detected in the short arm of the X. The study of C-band distribution showed that several autosome pairs and the X chromosomes had small masses of centromeric heterochromatin. On the other hand, the Y and B chromosomes were C-band negative. The Y-like chromosome in females with dimorphism of the sex pair was also C-band negative. Accordingly these females were considered to be XY and not Xx (the x being an extensively deleted X chromosome).
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This work was supported by grants from UNESCO, OEA, CONICET and CIC. Requests for reprints should be addressed to N.O. Bianchi.
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Lobato, L., Cantos, G., Araujol, B. et al. Cytogenetics of the South American Akodont rodents (Cricetidae) X. Akodon mollis: a species with XY females and B chromosomes. Genetica 57, 199–205 (1982). https://doi.org/10.1007/BF00056483
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DOI: https://doi.org/10.1007/BF00056483