: X-Y COMBINATIONS The X and one or both arms of the Y chromosome may be linked by recombinational events occurring in the heterochromatin. Such X-Y combinations are composed of the X, a centromere (derived from either X or Y), and either YL or YS or both. In the designation of such chromosomes, the component elements are listed in order such that the X precedes the centromere (symbolized by a center point), e.g., YSX.YL. Events that give rise to X-Y attachments are usually recurring so that the same combinations arise repeatedly; however, since the exact points of exchange differ, independent occurrences of similar combi- nations certainly differ from one another in heterochromatic content. Because similar X-Y combinations of independent ori- gin are not ordinarily designated, studied, or maintained as different chromosomes, and because for most purposes, it is not important that they be distinguished, for the most part, general categories of X-Y combinations are described in the ensuing section. Where a specific combination has been stu- died, it is listed with the designation of its component ele- ments followed immediately by its specific designation, e.g., X.YLC2. The complete designation of an X-Y combination consists of the following items in the order given: chromosomal elements, sequence of the X chromosome (if other than normal), gene con- tent. X-Y combinations that differ from one another only with respect to mutant genes or euchromatic inversions are not described separately because it is considered that such mutants and inversions can be removed from or inserted into the component X by euchromatic exchange. When X's differ by an inversion with at least one heterochromatic breakpoint, the chromosomes are described separately because they must differ in their heterochromatic constitution. # FR1: see YSX # Fragment 1: see YSX # mwh+YSX: see Dp(1;Y;3)M1-3 # sc8c.o.X: see YSX, In(1)sc8 # XY+: see X.YL # X.bw+YL constitution: X.(bw+-ba+) KL. X chromosome with prominent YL as second arm. origin: Spontaneous in y v/bw+Y; bw stock. synthesis: Erickson. synonym: Dp(1;Y;2)bw+. references: 1968, DIS 43: 63. properties: X chromosome originally carried y and v; Y arm car- ries YL fertility factors with bw+-ba+ inserted proximal to KL. # X.YL origin: A recurrent product of exchange between the proximal heterochromatin of C(1)RM and either arm of the Y. Also may result from exchange between YS and the proximal heterochroma- tin of a normal X or the interstitial heterochromatin of C(1)RA. Have also been recovered as one element of T(1;Y)'s induced in X/Y sperm with one break in YS and the other in X heterochromatin (Kennison, 1981, Genetics 98: 529-48). May be recovered with YL marked with various euchromatic markers, e.g., bw+ (Erickson, 1968, DIS 43: 63), y+, or BS. synonym: XY . references: Stern, 1926, Biol. Zentralbl. 46: 505-08. 1929, Z. Indukt. Abstamm. Vererbungsl. 51: 253-353. Kaufmann, 1933, Proc. Nat. Acad. Sci. USA 19: 830-38 (fig.). properties: An X chromosome in normal sequence with YL appended as a second arm. May carry varying amounts of the proximal part of YS between the X and the centromere; positions of such breakpoints with respect to bb, ks1, and ks2, as determined by Kennison for T(X;Y)'s provided with entries on the transloca- tions. Males carrying X.YL require KS in some form for fertil- ity. Chromosome V-shaped in metaphase. other information: A series of X-ray-induced exchanges between X.YL and y+Y replacing YL with y+YL investigated by Frankel (1968, DIS 43: 99; 1973, Genetics 74: 115-32). # X.YLC2 constitution: X.YL, bb- KL. origin: Recombination between YS proximal to bb+ and C(1)RM distal to bb+. synthesis: Lindsley. properties: Like X.YL but deficient for bb; X.YLC2/0 lethal. Shows unique behavior in double, first anaphase bridges (Novitski, 1952, Genetics 37: 270-87). Male sterile in combi- nation with y+Ymal+ (Stone, 1984, Can. J. Genet. Cytol. 26: 67-77). # X.YL, In(1)EN constitution: X.YL, In(1)EN, y.KL. origin: Single euchromatic recombinant from YSX.YL, In(1)EN/In(1)EN female. properties: An entirely inverted X chromosome with YL appended as a second arm. # XYL origin: Detachment of XYL.X or XYL.YLX (attached X chromosomes synthesized from XYL.YS) by interchange with small, free-X heterochromatic duplications, i.e., Dp(1;f). references: Lindsley and Novitski, 1959, Genetics 44: 187-96. XYL.YS From Lindsley and Novitski, 1959, Genetics 44: 187-96. # XYL.YS constitution: XYL.YS; originally y2 su(wa) wa (bb?) KL.KS. origin: X-ray-induced detachment in C(1)RM, y2 su(wa) bb/y+Y female; Y-chromosome breakpoint distal to kl5. Also a common product of X-Y translocation induced in X/Y sperm, at least when the Y is BSYy+ (Kennison, 1981, Genetics 98: 529-48). synthesis: Parker. references: Parker and McCrone, 1958, Genetics 43: 172-86. Lindsley and Novitski, 1959, Genetics 44: 187-96 (fig.). properties: Essentially an intact Y chromosome with all of the X euchromatin appended distally to KL. Carries all the sex- chromosome material required for male viability and fertility. other information: Several detachments of this constitution recovered (numbered 2-10T13, 2-10T15, 108-9, 112-17, and 129-11) as well as segregants from translocations with one break in X heterochromatin and one distal to kl5 in BS Yy+ (designated E12, E17, F6, K1, N16, P9, V13, and W8). XYL.YS129-16 # XYL.YS129-16 constitution: XYL.YS; originally y2 su(wa) wa (bb?) y+ KL.KS. origin: X-ray-induced detachment in C(1)RM, y2 su(wa) bb/y+Y female. synthesis: Parker. references: Parker and McCrone, 1958, Genetics 43: 172-86. Parker, 1968, DIS 43: 156. properties: Essentially an intact Y chromosome with all of the X euchromatin attached to YL distal to y+. Interstitial posi- tion of y+ shown by recovery of y+ reattachment; also inter- stitial y+ allele shows strong variegation. The break in the y+Y occurs between l(1)1Ac+ and y+ (Parker, 1968). Carries all the sex-chromosome material required for male viability and fertility. # XYL.YS, bb- constitution: XYL.YS, y v bb- KL.bb- KS; rDNA-deficient chromo- some carrying most of BS Ybb-; derived by detachment of the distal [In(1)dl49] X of C(1)DX and its attachment to YL of BSYbb- with loss of BS; In(1)dl49 replaced by recombination. synthesis: Komma. synonym: X-Ybb-. references: Komma and Endow, 1986, Genetics 114: 859-74. properties: A Ybb- chromosome with the X euchromatin attached (in normal sequence) distal to YL. Carries all the sex- chromosome material required for male fertility, but is defi- cient for bobbed. other information: bb/XYL.YS, bb- females show an increase in the number of 18S + 28S ribosomal genes (magnification) in their offspring. # X.YS origin: Recurrent product of recombination between the proximal heterochromatin of C(1)RM and the Y. Also recovered as one element of T(1;Y)'s induced in X/Y sperm with one break in YL and the other in X heterochromatin (Kennison, 1981, Genetics 98: 529-48). synthesis: Kaufmann. references: 1933, Proc. Nat. Acad. Sci. USA 19: 830-38. properties: An X chromosome in normal sequence with YS appended as a second arm. May carry varying amounts of the proximal part of YL between X and the centromere; positions of such breakpoints with respect to kl5, kl3, kl2, Su(Ste), and kl1 as determined by Kennison for T(X;Y)'s provided with entries on the translocations. Males carrying X.YS require KL in some form for fertility. Chromosome J-shaped in metaphase [e.g., Janning, 1970, Mol. Gen. Genet. 107: 150-57 (fig.)]. # X.YS, Basc constitution: X.YS, In(1)scS1Lsc8R+S, y31d scS1 sc8 wa B.y sc+. origin: Recovered as an X-ray-induced detachment from a C(1)RM, Basc/Dp(1;Y)1E female. synthesis: Ehrlich. references: 1971, DIS 46: 108. properties: Homozygous females viable and fertile; males viable and fertile with normal Y but lethal with Dp(1;Y)1E. Suppresses crossing over in X. # X.YSYL constitution: X.YSYL, y w.KS KL y+; metacentric chromosome. origin: X ray induced in X.YS, y w/y+ YL male. references: Johnsen, 1968, DIS 43: 158. Johnsen and Zarrow, 1971, Mol. Gen. Genet. 110: 36-39. properties: Attached XY with X in normal sequence on one side of the centromere and a complete Y on the other. X.YSYL/0 males fertile; transmission of the XY somewhat reduced. XYS.YL From Lindsley and Novitski, 1959, Genetics 44: 187-96. # XYS.YL constitution: XYS.YL; originally y2 su(wa) wa (bb?) KS.KL y+. origin: X-ray-induced detachment in C(1)RM, y2 su(wa) bb/y+Y female, in which the Y breakpoint is distal to ks2. Also a common product of X-Y translocation induced in X/Y sperm, at least when the Y is BSYy+ (Kennison, 1981, Genetics 98: 529- 48). synthesis: Parker. references: Parker and McCrone, 1958, Genetics 43: 172-86. Lindsley and Novitski, 1959, Genetics 44: 187-96 (fig.). properties: Essentially an intact y+Y chromosome with all of the X euchromatin appended distally to YS. Carries all the sex-chromosome material required for male viability and fer- tility. YL may carry any marker available on the long arm of marked Y chromosomes, e.g., y+, BS, etc. other information: Two detachments of this constitution recovered (110-8 and 115-9) as well as segregants from translocations with one break in X heterochromatin and one distal to ks2 in BS Yy+ (designated G7, N10, N30, P1, V4, V23, V25, V36, and Z14). # YSX constitution: YSX; originally KS y cv v f (Braver). origin: Spontaneous derivative from YSX.YL, In(1)EN, KS y.KL/sc cv v f. synthesis: Novitski. synonym: FR1: Fragment 1. references: Novitski, 1952, Genetics 37: 270-87. Lindsley and Novitski, 1959, Genetics 44: 187-96. Janning, 1970, Mol. Gen. Genet. 107: 150-57 (fig.). properties: An X in normal sequence marked with y and with YS appended distal to l(1)1Aa+. Reduces crossing over near y. # YSX, In(1)FM7 constitution: YSX, In(1)FM7, y+ KS y- wa vOf. origin: X-ray-induced detachment by exchange between the inter- stitial heterochromatin of C(1)M4 with the short arm of BS Yy+. references: Craymer, 1974, DIS 51: 21. # YSX, In(1)sc8 constitution: YSX, In(1)sc8, KS [l(1)1Aa-ac]- sc8. origin: Infrequent product of spermatogonial exchange between YS and the distal inverted heterochromatic segment of In(1)sc8. The incidence increased twenty fold in genotypes undergoing ribosomal DNA magnification [e.g., In(1)sc8, bbl sc8/Ybb], but decreasing with successive generations of mag- nification (Ritossa, 1973, Proc. Nat. Acad. Sci. USA 70: 1050-54). synthesis: Sidorov. synonym: sc8 c.o. X. references: Sidorov, 1940, Bull. Biol. Med. Exp. URSS 9: 10- 12. 1941, Dokl.Akad. Nauk SSSR, Ser. Biol. 30: 248-49. Lindsley, 1955, Genetics 40: 24-44. Ritossa, 1973, Proc. Nat. Acad. Sci. USA 70: 1950-54. properties: In(1)sc8 with the distal uninverted euchromatic region carrying the normal alleles of l(1)1Aa through ac replaced by KS; deficiency covered in single crossover between in(1)sc8 and In(1)EN, i.e., In(1)sc8LENR. Resembles In(1)sc8 in mitotic prophase. # YSXX.YL constitution: An X-Y combination carrying a C(1)RA; the distal X is YSX in normal sequence, and the proximal X is an inverted sequence with YL attached as a second arm. origin: Exchange in triploid females carrying C(1)RA, first replacing the centromere region of the proximal X with that of YSX.YL, In(1)EN and then the terminus of the distal X with that of YSX. references: Lindsley and Novitski, 1959, Genetics 44: 187-96. # YSX.YL constitution: YSX.YL, KS y.YL. origin: Recombination between YSX and X.YL. synthesis: Lindsley and Novitski. references: 1959, Genetics 44: 187-96. properties: An attached XY with the X in normal sequence. Con- tains all of the sex-chromosome material required for male viability and fertility. Commonly kept in stock as YSX.YL/0 males crossed to C(1)/0 females. YSX.YL, In(1)EN From Lindsley and Novitski, 1959, Genetics 44: 187-96. # YSX.YL, In(1)EN constitution: YSX.YL, In(1)EN, KS y.KL y+. origin: Recovered as recombinant between the proximal hetero- chromatin of YSX, In(1)sc8LENR and y+Y. synthesis: Lindsley, 1949. references: Lindsley and Novitski, 1960, DIS 24: 84-85. 1959, Genetics 44: 187-96 (fig.). properties: Contains all of the sex-chromosome material required for male viability and fertility. Exists without the y+ marker at the end of the YL arm. A derivative with BS at the end of YL described by Craymer (1974, DIS 51: 21); also exists with various combinations of sex-linked markers. Two X-ray-induced paracentric-inversion derivatives described by Novitski: In(1)24, a nearly complete inversion with one break in the normally proximal euchromatin and the other in the cen- tric heterochromatin, and In(1)26 with one break in 10A and one break in heterochromatin, distal or proximal not specified (Novitski, 1951, DIS 25: 122; Lindsley and Novitski, 1959, Genetics 44: 187-96). # YSX.YL, In(1)FM7 constitution: YSX.YL, In(1)FM7LENR, y+ KS y vOf.KL BS. origin: Recombination between YSX, In(1)FM7, y+ KS y- wa vOf and YSX YL, In(1)EN, KS y.KL BS such that the wa y- base of FM7 is replaced by the w+ y.KL of YSX.YL, In(1)EN. synthesis: Craymer, 74d. synonym: FM7Y. references: Craymer, 1974, DIS 51: 21. Mitchell, 1977, Genetics 87: 763-74. properties: Contains all of the male fertility factors. The FM7 inversions prevents euchromatic crossovers and the y+ and BS markers serve to detect recombinational events in the hetero- chromatin. # YSXYL. constitution: YSXYL., KS y KL.. origin: Rarely recovered recombinant between XYL. and YSX. synthesis: Lindsley. references: Lindsley and Novitski, 1959, Genetics 44: 187-96. Novitski and Brosseau, 1964, Genetics 50: 273 (abstr.). Donady, Seecof, and Fox, 1973, Genetics 73: 429-34. properties: Shows extremely reduced recovery from above hetero- zygous females (Lindsley and Novitski), all zygotes carrying YSXYL. being lethal in some autosomal backgrounds; reciprocal recombinant recovered frequently (Novitski and Brosseau; Donady et al.).