RINGS # R(1)1: Ring (1) cytology: R(1)1A;20B-C; salivary chromosomes show deficiency for most of 1A and a duplication for 20C-D [Schultz and Catcheside, 1937, J. Genet. 35: 315-20 (fig.)]. Ring shaped in metaphase. new order: |1A - 20.20F - 20C|. origin: Spontaneous from C(1)RM, y female. discoverer: L. V. Morgan, 1922. synonym: Xc; X0. references: 1926, Proc. Nat. Acad. Sci. USA 12: 180-81. 1933, Genetics 18: 250-83. genetics: Carries y. Male and homozygous female have reduced viability; X/0 male lethal (Schultz, 1941, Proc. Int. Congr. Genet., 7th., pp. 257-62). Somewhat unstable, tending to be eliminated during mitosis. Shows about 5 times as much somatic crossing over as rod X (Brown, Walen, and Brosseau, 1962, Genetics 47: 1573-79). Crossing over reduced in ring/rod heterozygote; only double crossovers recovered. Exceptional males result from 4-strand double crossing over in R(1)1/+ female. other information: May open out into a rod [e.g., In(1)EN] spontaneously in stock. # R(1)2 cytology: R(1)1A3-4;19F-20A1; salivary chromosomes deficient for 1A1-3 and reported to be duplicated for all of region 20 (Schultz and Catcheside, 1937; Viniika et al., 1971), but duplication was not confirmed by Falk (1973). Ring shaped in metaphase. new order: |1A4 - 20.20F - 20A1|. origin: Spontaneous as a detachment of C(1)RM, y+. discoverer: Beadle, 34b (ring nature discovered by Boche). synonym: Xc2. references: Schultz and Catcheside, 1937, J. Genet. 35: 315- 20. Viniika, Hannah-Alava, and Arajarvi, 1971, Chromosoma 36: 34-45. Falk, R, 1973, DIS 50: 144-45. genetics: Carries y+. More viable than R(1)1; X/0 male sur- vives. Ordinarily, ring elimination less than 1% (Batta- charya, 1950, Proc. R. Soc. Edinburgh, B 64: 199-215; Braver and Blount, 1950, Genetics 35: 98), but nearly 20% of the first progeny of 11-day-old females crossed to ring-bearing males are gynandromorphs (Hannah, 1955, Z. Indukt. Abstamm. Vererbungsl. 86: 600-21). Number of male nuclei in eggs of gynandromorphs varies greatly, suggesting that loss of the ring X may occur more than once and that it may take place as late as the ninth cleavage (Zalokar, 1980, Cell 19: 133-41). Crossing over reduced in ring/rod heterozygote; only double crossovers recovered. Exceptional males result from 4-strand double exchange in R(1)2/+ female. other information: Ring may open out spontaneously in stock [e.g., In(1)EN2]. # R(1)5A cytology: Ring shaped in mitotic figures. origin: Derived from C(1)TM5A by meiotic exchange between arms. references: Pasztor, 1967, DIS 42: 107. 1971, Genetics 68: 245-58. genetics: Mitotically unstable, producing gynandromorphs and XO males. Duplication of X required for male survival; R(1)5A/0 and R(1)5A/Y males not recovered; however, R(1)5A-bearing males survive in combination with BSY or su(f)+Y. # R(1)9-1 cytology: Ring shaped in mitotic figures. Early prophase shows heterochromatic constitution (proceeding from normally proxi- mal euchromatin, across the centromere to the normally distal euchromatin) to be as follows: a large segment, a well- defined constriction, a large segment, a constriction, a small segment, the centric constriction, a small segment. origin: Regular product of exchange in C(1)TMBS9-1. references: Lindsley and Sandler, 1965, Genetics 51: 223-45 (fig.). genetics: Carries y. R(1)9-1/0 male survives. On basis of origin, R(1)9-1 is euchromatically but not heterochromatically identical with R(1)1. # R(1)9-4 cytology: Ring shaped in mitotic figures. Early prophase shows heterochromatic constitution (proceeding from normally proxi- mal euchromatin, across the centromere to the normally distal euchromatin) to be as follows: a large segment, a constric- tion, a small segment, the centric constriction, a small seg- ment. origin: Regular product of exchange in C(1)TMBS9-4. references: Lindsley and Sandler, 1965, Genetics 51: 223-45 (fig.). genetics: Carries y. R(1)9-4/0 male viable. Based on origin, R(1)9-4 euchromatically but not heterochromatically identical with R(1)1. # R(1)63 cytology: Ring shaped in mitotic figures. Early prophase shows heterochromatic constitution (proceeding from the normally proximal euchromatin, across the centromere to the normally distal euchromatin) to be as follows: two large segments separated by an ill-defined constriction, a constriction, a small segment, the centric constriction, a small segment. origin: Regular product of exchange in C(1)TM2. references: Lindsley and Sandler, 1965, Genetics 51: 223-45 (fig.). genetics: Carries y. R(1)63/0 male survives. Based on origin, R(1)63 is euchromatically but not heterochromatically identi- cal with R(1)1; however, survival of R(1)63/0 males suggests otherwise. # R(1)94-2A1 cytology: R(1)1A;1F-2A;5E-6A;17F-18A;20; duplicated for 1A-F and 18A-20. new order: |1A - 5E|1F - 1A|20.20 - 6A|18A - 20|. origin: Spontaneous product of C(1)94-2A. Possibly a product of breakage of double second-anaphase bridge formed by exchange between the arms of the compound. discoverer: Armentrout, 1964. #*R(1)C1 cytology: Ring shaped in mitotic figures. origin: Spontaneous derivative of In(1)sc8LENR; arose by recom- bination between distal heterochromatic segment of In(1)sc8 and heterochromatic short arm of In(1)EN. discoverer: Lindsley, 1950. references: 1958, Z. Indukt. Abstamm. Vererbungsl. 89: 103-22. genetics: Carries y. On basis of origin, R(1)C1 is euchromati- cally identical with R(1)1, but it must be different hetero- chromatically since R(1)C1/0 male viable. # R(1)Ddc+ cytology: R(1)1A3-4;19F-20A1 In(1)3C1-2;20F + Ddc+ insert (near sn). origin: Double crossover between R(1)2, In(1)wvc and rod-X chromosome with P-element mediated Ddc+ insert. synonym: Ddc+-Ring-X. references: Gailey, Bordne, Valles, Hall, and White, 1987, Genetics 115: 305-11. genetics: Shows instability characteristic of R(1)2, In(1)wvC. Used to generate Ddc mosaics. # R(1)l-v459 cytology: R(1)3D-F. origin: Associated with T(1;2;3)l-v459. # R(1)y4: Ring (1) yellow cytology: R(1)1A8-B1;18A3-4; deficient for 1A and duplicated for 18-20. new order: |1B1 - 20.20 - 18A4|. origin: Regular product of exchange within inversion in C(1)SB; which is a C(1)RM heterozygous for In(1)y4 = In(1)1A8- B1;18A3-4. discoverer: Sturtevant and Beadle. references: 1936, Genetics 21: 554-604. Novitski and Sandler, 1956, Genetics 41: 194-206. genetics: Deficient for loci distal to y, duplicated for car- bb. Heterozygous female survives; male lethal, owing to defi- ciency for l(1)1A loci. # R(1;Y)EN cytology: Complete X and Y chromosomes joined together in a ring. origin: X-ray-induced exchange in tandem metacentric carrying a normal X attached to one Y arm and an inverted X to the other arm without loss of Y fertility factors. synonym: C(1;Y)R, EN. references: Fowler, 1971, DIS 46: 74. Novitski and Childress, 1976, The Genetics and Biology of Dro- sophila (Ashburner and Novitski, eds.). Academic Press, Lon- don, New York, San Francisco, Vol. 1b, pp. 487-503. Novitski and Puro, 1978, DIS 53: 205. genetics: Filicidal except in certain genetic backgrounds. Not obviously unstable. Neither the X nor the Y in the ring lack any essential viability or fertility genes. # R(Y) Described in section on Y derivatives. # R(2)Bl: see Dp(2;f)Bl # R(2)rl+: see Dp(2;f)rl+ # R(3)S1: Ring (3) Synthetic cytology: Ring shaped in mitotic figures. Duplicated for 89C- 92D and deficient for terminal chromatin of 61A and 100F. new order: |61A - 100F|92D - 89C|. origin: Synthesized from In(3LR)P88 + In(3R)C and a structur- ally normal 3 by crossing over in both the 61-89 and the 92E- 100F region. references: Craymer, 1984, DIS 60: 80-81. genetics: Duplication of 89C-92D compensated by Df(3R)P47 = Df(3R)89D;92A; R(3)S1/Df(3R)P47 flies have minor phenotypic abnormalities and are sterile or nearly so; a few fertile crossovers carrying Df(3R)P47 in the ring are fertile. other information: Ring useful for inserting markers into In(3R)C. # R(3L) cytology: Ring involving all of 3L. origin: Byproduct of synthesis of 3R3L.3R chromosome by X ray. references: Novitski and Puro, 1978, DIS 53: 205.