UNORDERED ARRANGEMENT OF CHROMOSOMES IN THE NUCLEI OF CHICKEN SPERMATOZOA

The arrangement of chromosomes in the elongated sperm nuclei of chicke n was studied using fluorescence in situ hybridization with probes spe cific for telomeres of all chromosomes, a microchromosome, the long an n of chromosome 6, the large heterochromatic block on the Z-chromosome , and the same heterochromatic block plus subtelomeric sites on macroc hromosomes 1-4. The positions of all probes vary from one sperm to ano ther. No order in chromosome arrangement is apparent. It is suggested that large chromosome size and small chromosome number correlate with constant positions of chromosomes and vice versa. Based on the known q uantity of repetitive units of the repeat on the Z-chromosome, the deg ree of compaction of chromatin in the chicken sperm nucleus is estimat ed as ca 0.7 Mb/mu m. As judged from the length of the heterochromatic region of the chromosome at the lampbrush stage, the total length of the Z-chromosome in mature sperm is 2.5-4 times that of the sperm nucl eus.