C(1;Y)6/Dp(1;f)YP223 males that are homozygous for mei(2)yh92¹ show a high frequency of non-disjunction of the sex chromosomes (18.1%) and fourth chromosomes (18.3%). Homozygous XY males show a high frequency of non-disjunction of the sex chromosomes (17.5%) and fourth chromosomes (8.7%). Analysis of the progeny of homozygous males mated to compound-X females indicates that mei(2)yh92¹ predominantly disrupts meiosis I. Homologous chromosomes are paired in prometaphase-metaphase I primary spermatocytes of homozygous males (as occurs in wild type). Defects are seen in homozygous males in the late stages of meiosis I; some chromosomes show a delay in migration to the poles or remain in the vicinity of the equator in anaphase I cells, while others have already moved a considerable distance to the poles. This asynchronous chromosome movement is seen in 43% of mutant anaphase I cells (it is never seen in control cells). Thin chromatin bridges are seen connecting daughter nuclei or nuclei associated with chromatin trailing behind at telophase I are seen. Homozygous female lay a large number of eggs with normal eggshell morphology, but nuclear divisions become abnormal by the syncytial blastoderm stage.

mei(2)yh92¹ males show about 20% non-disjunction between the X and Y as well as the 4th chromosomes. All homologous chromosomes are tightly associated at the first metaphase in meiosis in these males. Chromatin bridge formation occurs in 18% of first anaphase and telophase cells and the duration of the metaphase stage of the first division is prolonged.