Eliminates meiotic crossing over in homozygous
females. First-division nondisjunction and chromosome loss
frequent (30% for X, 2, and 3; 20% for 4); second division
normal; exceptions more frequent at 25 than at 19. Production
of triploids and intersexes 300-500 times normal. Egg hatch
very low. Synaptonemal complexes absent from oocytes (Meyer),
and both duration of meiotic prophase and number of 16-cell
cysts per germarium reduced in c(3)G/c(3)G females (Smith and
King, 1969, Genetics 60: 335-51). Meiotic loss of ring chromosomes increased in c(3)G females (Sandler, 1961, Nat. Cancer
Inst. Monogr. 18: 243-73). No meiotic effects in homozygous
males. In c(3)G/+ females, both intergenic recombination
(Hinton, 1966, Genetics 53: 157-64) and the subset of
intragenic recombination accompanied by recombination of
flanking markers (Carlson, 1972, Genet. Res. 19: 129-32)
increased. Somatic pairing (Semjenov, 1979, Tsitologiya
21: 1353-55) and somatic crossing over (Le Clerc, 1946,
Science 103: 553-54) normal in c(3)G homozygotes; however,
reported to be deficient for one of two X-ray-induced reactions leading to mitotic exchange (Handle, 1974, Molec. Gen.
Genet. 128: 233-39). Heterochromatic interchanges inducible
in oocytes of homozygous females by X irradiation (Roberts,
1969, Genetics 47: 387-408; Wurgler, Graf, Ruch, Beck, and
Steiner, 1978, Arch. Genet. 51: 217-42). Oocytes of homozygous females show increased sensitivity to X irradiation and
lack the normally observed fractionation effect (Watson, 1969,
Mutat. Res. 8: 91-100; 1972, Mutat. Res. 14: 299-307); Watson (1972) also reports increased sensitivity of c(3)G-bearing
sperm from c(3)G/+ males to translocation induction. RK3.
Effects slightly more severe than in c(3)G. Meiotic
recombination absent; first-division nondisjunction and loss
high (40% for X, 2, and 3; 30% for 4). Low level of nondisjunction in second meiotic division. Oocytes of homozygous
females lack synaptonemal complex (Carpenter).
Hypomorphic allele. Homozygous females show polarized reduction of recombination to 4.3% between y and f with
greatest reduction distally. X-chromosome nondisjunction temperature sensitive; 16.7% at 25; reduced to 10.2% in oocytes
exposed to 17 during metaphase I and anaphase I; no X-chromosome loss at either temperature. Synaptonemal complex
reduced in quantity and abnormal in structure.
c(3)GOR28/Df(3R)sbd105 females exhibit no recombination and
32% X-chromosome nondisjunction.