Chronology of DNA replication in the sex chromosomes of the reindeer ( Rangifer tarandus L.)

• Published in: Cytogenetic and Genome Research
• Main Authors: Fraccaro, M., Gustavsson, I., Hultén, Maj, Lindsten, J., Tiepolo, L.
• Format: Article in Journal/Newspaper
• Language: English
• Published: S. Karger AG 1968
• Subjects: The ''Y''; Rangifer tarandus
• Online Access: http://dx.doi.org/10.1159/000129984; https://www.karger.com/Article/Pdf/129984

The chromosomes of the reindeer (2n = 70) were studied with special reference to the chronology of DNA replication of the sex chromosomes. The X chromosome was metacentric and nearly of the duplicate type, being about 9% in length of the total complement. All the other chromosomes, including the Y, were acrocentric except one submetacentric pair. The X and Y chromosomes were apparently terminally associated at first meiotic metaphase in the male. A single, rather large chromocenter was observed in the majority of cultured female cells. The male cells were predominately negative but occasionally demonstrated a somewhat smaller, distinct chromocenter. Autoradiography showed that in the female cultured cells the ‘one entire X plus half of the other X heavily labelled’ pattern was conspicuously present at the end of the S period. A quantitative analysis indicated that one hour from the end of the S period both X chromosomes were uniformely labelled. One X was still completely labelled, while one arm of the other was not 45 min before the end of S, and at 30 min only one arm in each X chromosome was labelled. The two X chromosomes then seemed to be slightly asynchronous until the very end of S. In the male cells semiquantitative analysis indicated that one arm of the X and the entire Y chromosome were synchronous in terminating DNA synthesis.