Multiple chromosome masses are seen at metaphase I in 15% of homozygous oocytes.
Mutant oocytes have precocious anaphase and anaphase II spindles.
The frequency of region 2b and region 3 cysts with two pro-oocytes (as assayed by c(3)G staining) in homozygous females is not significantly different from that seen in wild-type females.
Mutant females show reduction in the overall frequency of crossing over on the second chromosome compared to wild type. The reduction in crossing over in the centromere-proximal interval is more modest than the total reduction in crossing over frequency.
Crossing over is reduced to a frequency 3-7% of wild type. Reduction in crossing over is twofold less in the centromere proximal regions compared to the distal regions. High levels of nondisjunction on the X chromosome, lower levels on the 4th chromosome.
Recombination in females is reduced to 8% of control levels. Chiasma frequency greatly reduced. Stage 14 oocytes can finish both meiotic divisions without metaphase arrest. Rare normal metaphase figures indicate that even one chiasma is sufficient to ensure metaphase arrest.
Increases the frequency of X chromosome non-disjunctions in noda mutants.
Reduces meiotic exchange. Nonhomologous exchanges are occasionally produced.
Females homozygous for mei-218 exhibit reduced levels of meiotic exchange. The residual exchanges are distributed such that the probability of euchromatic exchange becomes more nearly proportional to the polytene-chromosome length (Baker and Carpenter, 1972; Carpenter and Sandler, 1974; Baker and Hall, 1976). This relaxation of the normal constraints on the distribution of euchromatic exchange is clearly demonstrated by the ability of mei-218 females to allow exchange between the normally achiasmate fourth chromosomes (Sandler and Szauter, 1978). mei-218 does not, however, permit exchanges to occur in heterochromatic intervals (Carpenter and Baker, 1982). Ultrastructural analysis of pachytene in mei-218 and mei-2186-7 females demonstrates a reduced number of late recombination nodules (to about 8% of normal), which are distributed in a fashion that parallels the residual exchange events (Carpenter, 1979; 1989). Many of the nodules which are observed are morphologically abnormal. There is also some evidence that early recombination nodules may be either fewer in number or more ephemeral in mei-218 females (Carpenter, 1989). Although mei-218 alleles reduce the frequency of reciprocal meiotic exchange, the absolute frequency of gene conversion at the rosy locus is two-fold elevated relative to wild-type controls (Carpenter, 1982; 1984). Moreover, co-conversion distances are shorter than those recovered from controls or from mei-9 females (Carpenter, 1984). Thus the function of this locus is required for the generation of reciprocal exchanges and not for gene conversion (Carpenter, 1984). The reduced levels of reciprocal exchange which are characteristic of mei-218 females allow for high frequencies of meiotic loss and nondisjunction (see Baker and Hall, 1976). Nondisjunction occurs at the first meiotic division and only nonexchange chromosomes nondisjoin (Carpenter and Sandler, 1974). All assays for an effect of mei-218 on mitotic chromosome behavior in males or on somatic chromosome behavior are negative (Baker and Carpenter, 1972; Baker et al., 1978; Lutken and Baker, 1979; Gatti, 1979).
mei-2181, nodDTW has abnormal meiotic cell cycle | female phenotype, suppressible by lwr05486
mei-2181 is an enhancer of female sterile | recessive phenotype of spn-BBU
mei-2181, mei-9a has abnormal meiotic cell cycle phenotype
mei-2181, mei-W68Z4472 has abnormal stress response phenotype
mei-2181, nodDTW has abnormal meiotic cell cycle | female phenotype
mei-2181 is a suppressor of presumptive oocyte phenotype of hdmg7
mei-2181 is a suppressor of presumptive oocyte phenotype of mei-9a
mei-2181 is a suppressor of presumptive oocyte phenotype of spn-BBU
mei-2181 is a non-suppressor of stage S1 oocyte | increased number phenotype of Scer\GAL4VP16.nanos.UTR, pch2UASp.Tag:HA
mei-2181 is a non-suppressor of stage S1 oocyte | increased number phenotype of c(2)MEP2115
A small but significant proportion of eggs produced by mei-2181/mei-2188 ; yemα1/Df(3R)3450 females are able to develop into adults. These exceptional adults do not display paternal chromosome markers, suggesting that they have developed from diploid gametes that have undergone gynogenesis, a form of parthenogenesis that requires fertilisation.
The high frequency of region 3 cysts containing two pro-oocytes that is seen in hdmg7 homozygous females is suppressed by mei-2181.
The high frequency of region 3 cysts containing two pro-oocytes that is seen in mei-9a homozygous females is suppressed by mei-2181.
The high frequency of region 3 cysts containing two pro-oocytes that is seen in spn-BBU homozygous females is suppressed by mei-2181.
mei-W68Z4472/mei-W68Z4472, mei-2181/mei-2181 double mutant females exhibit less crossing over following irradiation, as compared to mei-W68Z4472/mei-W68Z4472 single mutants.
mei-9a/mei-9a mei-2181/mei-2181 double mutant female meioses exhibit a lower frequency of recombination, as compared to wild type, and a lower frequency of post-meiotic segregation, as compared to mei-9a/mei-9a single mutants.
Simple meiotic gene conversion tracts produced in mei-2181 mutants have been compared with those produced in wild-type.
The fraction of viable zygotes produced by homozygous females (25%) is no greater than would be expected based on the inviability of aneuploid zygotes receiving zero or two maternal copies of an X chromosome or a major autosome.