Haveh 1, 195) mel me2 spreac of mutational enance alonn chro : a control a 3 1 > syst'ms I. Review of previous discussion! 1. Presented evidence showing tnat b.P.b, cycle results in alterations in heterochromatic elements of chromosones of complement -- contromeres, ends, mobs and nucleolus organizer, 2. Because new mutable genes apreared in proreny of b.f.b evele »lants, the relationship between altered hete rocnaromatin and their annearances suspvected, 3. Presented evidence of induction of Dt-tyne action in endosperms undergoing b.f.b. cycle whore a, homozygouse lh, Gave reason for expecting dots of A, in sectors -- the state of the aj recessive: Produces dots of A, in presence of Dt, 5. Recent work with a. - Dt system, Chances in state of a found: produce early muteati ns to A; and to pales, ‘This done by Nuffer at Missouri, 6. New »ositicns of Dt found: a). Mhoades: Dt in his strain located at or &n lmob in snort arm of chromosome 9, d). Nurfer, analysed strains of maize from South America to sce if Dt might be present i> them, “ound Dt unit in two strains: One from Feru and one from Brezil, Both of these Dt units bensve just as Dt dis scoverod by HNhoades, Can not be distinguished from one anoth:r on basis of ee of a Positions of Dt units in ¢chromesone corrmlement: One ana vyseds3 not in chro:csov7e 9 but 13 kage with i suggest it is located in chro-csov-e 6S this expected, if Dt like Ac, Can heve it loested in farious varts of the chromcsome cormlement,. These results bring resemblance of 4,-Dt syston closer to that know concerning the Ds ~- Ac system, The someuic tegregation found in early sectorials need further investisaticn for similarities, In the ay Dt system of Rhoac OS, hidden mutations very much suspectocd on basis of distripyvtion of dots in the kernels -= not random, but in sectors, II, Today - wisn to show other tyves of systems than those previously discussed 1. One i volves the s-read of mutational changes along toe chrevos7:e i-dcuced by aventis at Ds. 2, “he other two involve the action & controlling svstens thot from those of Ae or Dt, 3. o time to develop the analysis in det4l Itust describe ¢ ben tvior without much documentaticn this cime. III, the smread of mut atlonal chance alone the chro -osovue, . : 1, Kow discovered: Jn analysis of “two cases wosre Os between + and Sh, but close to Sh, I Ds Sh Bz 2einitial tests, showed Ds very close to Sh, : > 4 ; « * © “~ desermine the crossing over betyeen Ds and Sh, 3, The tryoes of tests: T qorh = 32 Wx CAS SS br x C ds sh bz wx, a). With Ac n heterozyrous ouverts “ne test: 5907 ksrnels,. Cnly one kernel that mignt be oO a crossover betveen Ds and Sh found, I Ds sh bz wx kernel. b). 37 excentional kernels found: these were ~ Ds sh Bz in vhenotwe, a nereencneereoee tere eens inycae tor em 1 Nee hia Could not be due to double-crossovers; No reciprocals: Sh bz. c). when no Ae in hetcrozygous parent, crossed to C sh bz wx AC, no 4 exceotional kernels found; no crossovers between bs and Sh either, d), Susmected that the exceptional kernels with | as sh Bz wee produced by change in action of 5h to sh from Ds event, 4. The tests of the homozygotes: DsSh Bz Ac or Ac x G sh bz wx no Ac Ds Sh Bz ac Ke The results: parentege in cross I Sh Ish "C'Sh "C" sh _sitotals Female 2,365 16 22 3 21106 Case I Male 11,l2 12 16 22 11,622 Female 9,082 18 55 2 9,157 Case II Male 5,cok ht h PO I 5 Olly IV. fests cof the I sh kernels: 37 were I Dssn Bz, 12 were I Ds sh bz 1. The I Ds sh Bz ke-nels: a). In 9 of 37 cases, reverse mutations to Sh occurred, fio chanre in ‘ s » » ik cy * a L Seer nen Ds location in the reversions, two of 9 higuly miteble: mu eee A ARR He aR EEE teat I Dssh - I DsSh -IDssh ODs not removed wien muteticns occur, nor changed in location, — : b). One o: the micbles: crossing over groatly modified: Increased 50 % over standard in I to Ds region, and 3005 over standsrd in Dssh Bz region, this anvreores even when mutetion to Sh occurs, tests conducte: over three generaticns -+ crossing over remains high, ec), Cther cases whore reversions occur == no change in erossine over in marked regions : I to sh, and sh to Bz, d), Among the non-revaérsicn group: Distinguished from one another on basis of crossing over: some show normal ariount; some show reducticn in sh to Bz intorval; some show no crossine over in sh to Bz interval and reduced amount in I to sh interv-1, e). In all 37 cases of mutation te sh, normal mele and fenale t-nemicsior and viable honozvgotes, f). Vonelusions: Mutation to sz occurs when Ds to left of Sh but only when Ac vresent, No change in location of Ds ween tig ce-urs3; mutants differ from one ancther on besis of presence or ansence of reversions, and on inercases or decreases in crossing over in I to so, and sh to bz in-ervels. - 3- @). In one case - Case II = Ae in chromesom majority of the I Dssh kernels, locstion or stat with apnesrance of mutaticn, @ 9, to left of I, In of Ac was altered coincidentl oO 2. The I Ds sh bz kernels 12 case a). tlarked differences exhibited among tnen: Plant from one kernel -- bz; non-muvable; no pollen and no kernels formed, Com: letely male and female sterile, Uthe s differed with rerard to presence or aosence of reversions; n viabilities when heterozygous and homogyeous; in transmissions terough 3 ale and female eametes, a ib b). These 11 formed a graded series, (1). @h and bz phenotzyves: Normal male and fenale transmicsio Ds present, to b&fbt of bg and right of I. Normal homozvygotess rev: sic to Bz in presence of Ac but rate very_low, No reversions to Sh noted, Chromosome: normal, Crossing over 4 to sh normal; not tested between Sh and bz, NS 3 a 3 rata (2), Exactly like above, except that no reversicns of sh or bz noted, (3). Reduced transmission of chremescme carrying the Ds sh bz modified segment.thrceugh male; no reduction through female; homozygote very inviable, Chromcscome normal; crossing over I to sh normal (4.). Very much reduced transmissions through male of chrcvosome carrying I Ds sh bz sepment. Normal transnissions througn females; no homozygotes; hetorozygotes (1 dose of Ds sh bz segment) very abnormal and quite inviable in some kernels, Chrovcsove normal in morvchologys crossing over to either side of modified segment normal; no crossing over wit in Segment noted, (5) No transmissions through pollen of chremosone carr ing segments reduced transmissions throug females; chrom-sc-as normals very inviable heterozygotes (1 dose); normal crossing over I to sh and Leyord be, No crossing over within segment noted, No reversions. ec). In all cases, Ds present. Ds sh bz formed a unit in inhcoritance, in casés where reduced transmissions OCCULrs ad). the inviabilities of the neterozygotes -- dominance -- not due to a deficiency, Deficiency of whole short arm of one chro csome -« normal kernels. e). Conclusions: A Ds event, resulted in change in action of Sh and Bz cotncidently. Produced only when Ac present, No cnange in location that is marked noted, Reversions in only one case -- and this a case of normal transmissions and viahilities’ of nemozygotes, Spread of muktional effect probably beyond Bz as indicated by the inviabilities encountered, No chanre in chronosone morpholosy noted in any case, me! -lpe V. The svread of change along chromosome from Ds to I, 1. The "C" kornels in table: These expected on follow ne reasoning: Females? Ds break: Ses I Sh Bz > ¢ ~ Sh Bz I 2 ne = * One-third of short arm eltminated: this is not sufficient deficiency to eliminate functioning of female sametopnyte, In cross: would exvect C Sh Bz kernels from this and they should be variegated for bz due to b.f.b. ecveles 2, On the ears, some of the C kernels showed expected bz variegation: others did not snow this variegation, Some exnected not to show b.f.b evycles: ransloc: tions, non-reciprocal could occur oecasi nally to produces ° @ee@eoeeeteoesen Sh B6 - 3. The anelysis of plants from the two types of C kernels: 10 from CBz - C bz variegated caass: All as expected: o 6 a wes = .- e wet ite on eh é. ¢ * e ie ace ea No Ds present in tests of subsequent generations. 10 from the C Bz, not obviously varierated class: 2 -- non-reciprocal translocations: Po & - No Ds. 1 -- former dicentric, centromere removed from one chromatid. No Ds, 7 li, The remaining 7 in the C Bz, not obvicusly var. classe a). All had normal chro-osomes 9, b), All had Ds, just to left of Sh, ce), Divided into two classes on basis of genetic behavior’ > l -- Reduced transmi sion of the Sh Ez chromosome througn male, 3 -- No transmission of Sh Bz chrov-osene throuch melee ad); The homozygotes: In lh cases: colorless kernels. lhe heterozygotes : ow lored kernels, = "Red T” DoINRy Red I Ds Sh Bz Crossing over Red-I to Bh, -- none, ~ " " Sh to Bz -- normal. C ds sh bz . e). Lhe seedlines from the homo_vgotes: green -- albinescent - dies, All four cases exactly alike in these respects. f). The three remainine cases: Like above, except no male transmissions of chroioso7es with the "red, I". Form good homozygotes with other lp cases, however. &). Gonelusicns: Ac io n of I, or a deficiency, not seen, to left of Ds. - Ds not removed by tis. PO t C ing over in al “Peeted. seement not seen, VI. General conclusions 1,lGenes close torether in this case. Ds in the middle, ee Changes occur to both right and altered in locstion wnen change in gen left of Ds but Ds not removed or markedly nic acticn occurs. 3. These changes are relatively rare -- see table -+ but methods used will find them readily. This not essvy in cascs where Ds not close to aeveral loci -- tne majority of cases, lL, Analysis reveals spread of mutational changealong chromcsome, Not always deficiency, as the ca:c of bz to Bz coincident with sh bz mutsticn SHOWS « as but Ds always vresont in these cases, Also, a heterozvrous deficie ency, incass of Ds sh bz not the explanation, 5. Deficiencies not probebly -= should lose Ds in many case 6, these rare esses can explain the few cases, in study of ec-ml, where reversion to © not accompanied by loss of Ds. It remained very close to ©, Also, some kernels thet rev rted to mutehle condition noted -- anagin, rare. CDs -c to C3 This CDs gives c-rmiable arain,) The system controlling evnts at a.-m2 A/a Ds and Ac i First appesrance: in culture having mpwmk. Change at Ay; found in ngle kernel following cross of female by aj/a, a fed bse 2. Two classes of miuatio Class I, -- To highe er, smooth over alesrone laye ns: vr alleles of normal Ay Kernel dark color; color Plant: Dark color; leaves colored in blade, Class II mutes. tins: Very diffcrent: Diffuse -mottoled: Quantative expressions from nearly colorless to very dark, Plant: color in sheath, glumes, but none in the blade except in mid-rib and edge of leaf Sun colored ~- vequires much sun to form dark color: Unner and lover sides of glumes show this Mutetions of both classes are stable, No relation between color in kernel in diffuse-mottled class and color produced in plant by same mutation, An almost colorless kernel can produce plant with dark color. 3¢ Mutatio s occur in vlants =~ can recognize both tyres resdily, Plants derived from v~ rieprated kernels -- will SrOW both classes or mutaticns, h. The germinal mutaticns: To full A, and to the diffuse mottled cahass, All stable in subsecuent gsencrations, 5. The frequency of germinal mutations? isxamples:s O nn s s a,-m2/a,; m-2 female x a, [a male 16 ears: Full Ay diffuse-mottled variegated for both types of mutanticns, 105 955 2751 Total -- 3811 1/h -- 953. Hach of the diffuse mottled mutations a new One» 5 ears Full A, diffuse-mottled variegated for both types of mutations, 31 309 579 total -~ 919 1/3 -- 306 lh ears Pull Ay diffuse-mottled variegated for both tyros of mutants L? 16 3h total ~- 899 B -- 19.5 Through male -- often same types of ratios observed: Ay diffuse-motthed variegated totals 3:1 ratio 25 180 53 678 = 1/l 169.5 l:l 95 1391 1356 262: & W221 yy 7 — ya ye 8 6. When mutant sector present on ear: a mn2 Zz a, x a, /a, / ah one \onande See Atay. ON afer Quagcr ; d). this phenotype appears generation after generation as stable, Wil t . Fit become mutable when V added: “hen, color of background - to full Aq. Amain, some of the rale areas, colorless, mutation. e). the V shows dosages -- seen in other states very clearly -- controls time of change to futl Ale Something like Ac in t-is respect. d). Linkare of V found -- First linkarce - chromosome 6, Tsble on board, \ 63 Ns 100 \ lls LG. SH Totals 369 3764 336 34 LL $92 379 LbUt Fie Veh LHATL AY bb% élb ($e SIP JO. “UW wea het a} , inte wo TOT ywR kun aay pf Raval ‘oso + a aggarn “fp an © Jew U0 \z Gat A Yg8 = o~