Identification of X and Y spermatozoa in the northern vole, Microtus oeconomus.

The introduction of a quinacrine staining technique for identifying human chromosomes (Zech, 1969) also permitted recognition of the human Y chromosome in non-dividing cells (Pearson, Bobrow & Vosa, 1970), including spermatozoa (Pearson & Bobrow, 1970; Barlow & Vosa, 1970). The ability to distinguish between human Xand Y-bearing spermatozoa has been used in estimating the difference in the DNA content of these spermatozoa (Sumner, Robinson & Evans, 1971; Pearson, Geraedts & Pawlowitzki, 1973), the primary non-disjunctional frequency of the Y chromosome (Sumner, Robinson & Evans, 1971; Pawlowitzki & Pearson, 1972) and, more recently, for judging the success of a separation technique for X and Y spermatozoa (Ericsson, Langevin & Nishino, 1973). Chromosomes 1 and 9 have also been recognized in human spermatozoa (Pearson, 1972; Bobrow, Madan & Pearson, 1972; Geraedts & Pearson, 1973) by using variations in C-banding techniques which specifically stain the centric heterochromatin regions of these two chromosomes. There appear to be certain similarities in the staining properties of the chromosomes which have so far been detected in spermatozoa. The following criteria are accepted for recognition of chromosomes in spermatozoa : (a) there is a region of centric heterochromatin localized on one particular chromosome which can be stained and recognized uniquely in mitotic chromosome preparations; (b) the heterochromatic region remains visible in interphase nuclei as a differentially stained body; and (c) the latter is also visible through all the meiotic series into