SECOND-CHROMOSOME BALANCERS

# CyO:  Curly of Oster
 constitution:  In(2LR)O, Cy dplvI pr cn2.
 order:  21-22D|33F5-30F|50D1-58A4|42A2-
   34A1|22D2-30E|50C10-42A3|58B1-60.
 synthesis:  Oster.
 synonym:  Cy, InsO5.
 references:  1956, DIS 30:  145.
   O'Donnell, Gerace, Leister, and Sofer, 1975, Genetics
    79:  73-83.
 properties:  More effective suppressor of crossing over in chro-
   mosome 2 than In(2L+2R)Cy; should be superior to SM1 as a
   balancer for chromosome 2.  Other markers introduced into CyO
   include AdhnA and AdhnB (O'Donnell et al.), l(2)DTS100,
   l(2)DTS486, and l(2)DTS573 (Falke and Wright, 1972, DIS
   48:  89), as well as b, bw, esc2, pk81h, Roi, sple81h, and
   others.
# SM1:  Second Multiple 1
 constitution:  In(2LR)SM1, al2 Cy cn2 sp2.
 order:  21-22A3|60B-58B1|42A3-58A4|42A2-
   34A1|22D2-33F5|22D1-22B1|60C-60F.
 synthesis:  R.F. Grell, 1953.
 references:  Lewis and Mislove, 1953, DIS 27:  58.
 properties:  Homozygous lethal.  Viability and fertility of
   heterozygote excellent.  Reliable balancer for all of chromo-
   some 2, although there is an occasional double crossover in 2R
   if X and 3 are heterozygous for inversions.  MacIntyre and
   Wright (1966, DIS 41:  141-42) found no recombination between
   In(2LR)SM1 and al dp b pr cn c px sp in females heterozygous
   for In(1)sc8 and In(3LR)Ubx130.  Nondisjunction of compound
   autosomes occurs in SM1/+ females [Lindsley and Grell, 1969,
   Genetics 61 (Supplement):  69-71]; balancer shows interchromo-
   somal effect (Parry, 1973).
#*SM2
 constitution:  T(2;3)SM2, al2 Cy ltv cn2 sp2.
 synthesis:  R.F. Grell, 1953.
 references:  Lewis and Mislove, 1953, DIS 27:  58.
   1954, DIS 28:  77.
 properties:  Not useful as a balancer.
# SM5
 constitution:  In(2LR)SM5, al2 Cy ltv sn2 sp2.  Series of over-
   lapping inversions and transpositions distributed over length
   of chromosome (Sankaranarayanan, 1974, Mutat. Res. 24:  389-
   93).
 order:  21A-21D2|36C-40F|29D-22D2|34A1-
   36C|21D3-22A3|60B-58B1|42A3-42D|42D-
   43A|58B1-58F|53C-42D|53C-58A4|42A2-
   40F|29E-33F5|22D1-22B1|60C-60F.
 synthesis:  R.F. Grell, 1953.
 references:  Mislove and Lewis, 1955, DIS 29:  75.
 properties:  Homozygous lethal.  Heterozygote usually has good
   viability and fertility, although may not be as good as SM1.
   Most complete balancer for chromosome 2.
# SM6
 constitution:  In(1)2LR)SM6, al2 Cy dplvI cn2P sp2 combination
   containing both In(2LR)O and In(2LR)SMI.
 order:  21-22A3|60B-58B1|42A3-50C10|30E-
   22D2|34A1-42A2|58A4-50D1|30F-33F5|22D1-
   22B1|60C-60F.
 synthesis:  Craymer.
 references:  1984, DIS 60:  234-36.
 properties:  Suppresses recombination over entire chromosome 2;
   carries cn2P, an amorphic  derivative of cn2.  Two versions:
   without Roi = SM6a; with Roi = SM6b.