H 3 -THYMIDINE UPTAKE BY A RING X CHROMOSOME IN A HUMAN FEMALE

Abstract

H3-thymidine was used to label peripheral leukocytes obtained from a female with gonadal dysgenesis and a karyotype XO/XXR/XXRXR. The ring X chromosome is the only late-labeling X chromosome in metaphases containing a late-labeling chromosome. The pattern of DNA synthesis in the ring X resembles that found in other X chromosomes studied in a similar manner. The relationship of the nonrandom late-labeling pattern of the ring and other morphologically aberrant X chromosomes to the "Lyon Hypothesis" is discussed.