Transmission rate through females to progeny is 28% in the first 5 days of egg lay. SM1, TM3 and FM7c balancer chromosomes have no effect on transmission. FM7a-nod4 balancer chromosome causes a mild reduction in transmission. Heterozygous deficiencies can have strong effects on the transmission of the chromosome.
Exhibits moderate instability in a monosome transmission assay; transmitted to only 27% of the progeny.
Transmission rate through females to progeny is 28% in the first 5 days of egg lay. nod, ncd and Klp3A mutations strongly decrease transmission. One or two extra copies of nod provided by P{flag-nodhsp} partially rescues transmission. mei-S332 ord double mutants amd ord mutations cause a mild reduction in transmission. Other ord and mei-S332 mutations, grau, cort, mit(1)15 or wapl mutations have no effect on transmission. rod mutations cause a mild increase in transmission.
Contains only 290kb of centric heterochromatin.
Acentric mini-chromosomes are lost at a moderate but elevated rate during male germline mitotic divisions and in female mitosis, but appear to be transmitted efficiently through pre-blastoderm mitoses and male meiosis. mit(1)15 can localise to the mini-chromosome. Acentric mini-chromosomes are normally inherited, transmission is achieved by a mechanism similar to normal centromere-containing chromosomes, which utilises nod and mit(1)15 and involves movement to the spindle poles. Newly generated acentric fragments from the tip of the normal X chromosome do not display neocentromere activity in male meiosis I.
Minichromosome is 580bp in length.
Monosome transmission behaviour from both male and female parents is moderately unstable, heterochromatin contains only all of Bora Bora.
Used in experiments that showed that efficient achiasmate homolog disjunction in female meiosis I requires 1000kb of overlap in the centric heterochromatin and is not affected by homologous euchromatin or overall size differences. Disjunction efficiency decreases linearly as heterochromatic overlap is reduced from 1000 to 430kb. Rescue experiments with nod transgenes showed that heterochromatin does not act solely to promote chromosome movement or spindle attachment. Centric heterochromatin seems to contain multiple pairing elements that act additively to initiate or maintain the proper alignment of achiasmate chromosomes in meiosis I.
"Terminal" deletion.