I. Review of pxvicus disucnssion 1. Began consideration of the change at a normal D gene to give a mutable condition -- from recessive, colorless, c, to full color, C. 2. Condition found in 1 of 35'00 tested gametes from an Mngle plant whose cor_sltl:t$on ?~as: c skr wx Ds AC C Sh vx Ds ;tC 3. It was shown that mutzticrs to C OCCIU on2.y in z?esence of AC 4. ijithout AC, the colorless n5enoty?e, recessive, com;2letelp stabt2e; Xhen AC added to nucleus by ap`:`roprinte CTOSS, rmtati~ns commence, II. The stability of the C mutant from c-ml: 1, The mutant a:Teas in c/c/c-ml kernels: 2. The ger:xinal. mutati~:ns: iOFJ formed: c/c-ml AC ac Crossed to c/c: Few fully colored kernels. Those ewe from mutnticns at c-ml before gmtste formation, 3. Tests of the stability of Vne C mutants: a) Test ty->e I: Single kernel, frori~ ai>ovc cross. Self-pollinated for transmission of C mutant and ho~ozypous c.e:2dition Crossed bg kc-tester to determine presence and q n anr:enre or AC Crossed to c /c, ds ac -- to test fo- C p:?.enot;;oe. Cross::d to c / c AC. -- to test for reaction of C in p;-enence of AC, sPcoue d it be absent f'ro~? the plant beins tested, i'ic sul. t s : The C action coxnletal: stable in We presence of AC, b). Test type 2 - progeny test from a kernel. si-cl-e gemG.zml mutation car-;-.--ing Self-pollinated ear derived rrorn plant ~5th mutant U : %zmel.s of all tyges selected; Tested as above, Aesults: The same as above. i-iutnat C as s-kable as C f' ~y)y7A ?;J *! ; CA-& it was derived. III. _i The ?yresence of Ds in the c-ml cnrryin~y cI`Iro:wso:7e. 1. iriginal cross: ygc sh tm ds ac female 23gC Sil wx 9s AC YgC ;;ii-=- male QC 3. ConsicitI.:. Jticn cf plant was: 3 :'\sh wx ( > AC yg c shwx ds 2.c 4 o ? sh wx ds ac female X c-r?J Sh wx AC --- --..--. --.. C sh 2X =LC ,\\ c"Sh wx AC non-crossovers ..j ,- \ c s-l w-x no AC cr@SGOVCrS, region 2 and &pected a;;~e::.iyance C to c v3.r. colo~~less Sh :7x C t0 C Sh i'JX colorles:; sl?. lix c to c ST? i,Jx c Sn I-Jx (Crossovem) - i a). Ds &lose to or at the 1ocv.s of C -- that is, c-ml b), No Us at the standard loccticn in origin?1 r;lant. i c). 14utatio3s to C ascocT.zted wit!1 loss of Ds activ:it:: at I;he c locus. d). No cros~ov~:rs betr:oen c-ml and 1)s observed. NO kernels found yjith I ' e) Ds actlv5.t.g :~,ritl?out c to C 72utatI ens, I ' Nut9tic ns to C occur' on7.y r-ken AC c:?escnt. { L f) . Can beGin to conside:- the ?~ossib3Ji.t:,: that c-xl z~ose though txm.sposit~.on of I)s t0 tile C loCus, C&3 -- colorles?; action of C in--i.t:!ited. Loss of 13s Tram t;lis locus -- rett:rn of C action. IV, Attexl$s to rexlove Ds by crossing over -- to get a "mxztaticn to c!! 1. The test: Yb c sh wx ds ac fexK!..e x Yg c-ml Sh 'Yx ac male .P -- 3TQ c sh wx ac %Gkatarossed to AC tester cr+ocsed to c AC to test for c-YJ 20,000 kextels Tram the test cross -- none sl2owed any C ColoT, V, Attempts to rexove Ds from C by byeakage-fusion-bridge cycle. This a small test, Not many kernels enalysed, 1. The cross: Re c sh 1%~ ds ac female x c-1717. S1-1 Ux ac male. = - - . . n 3. `The crossovers -- the anaphasc bridges: I! 4. The transmissible gametes: % --+------- -- 4%' 44&h 0 . * -=: 5. The results: ~JO cases found where color aprearddq Larger test probo.;:ly would hnve s,+o~m this Sma11 test. -- i"ormatisn of a new AC factor, 6. Conclusions: of it, Ds mu&t be very close to the C gene I:ossibly a component Or kresence of Ds alters cross?ng-over: Reduced llero. kkatever the explgnation, the DsC sltuntZon acts as 2 unit, Changes in state o_f c-H _-- 1, The original stxLe of c-ml. Appearance of kernels with: c wx/c wx/ c-ml IJx, AC ac ac The sectors with altered actiofi: `; Found few kernels with whole area like one of t?:e des!zx?.bed seclvo~s. 2, Plots groom from the selected karnels dth altered numixr of mutations to C and numy;cr of spots rela-t? onships betxeen of tjlx carefully . EkcI2 kernel examined and pattern analysed, a). Iiange of selections: From very much increa? -ed Lrre-uency cf c to C mtations and no ux areas to those in w::.ich there woe only a few C specks and many wx areas, 3. Each ;-lant derived from t`ilese kernels crossed to'E/cy& female plants, Variegated kernels on resulting ear co3pc:red with each other and with patterneap-~c;;ing on the kernel Prom w`-fci~ plant arose. in kernel '" S' t: plant arose. the )>attern of variegation resembled that/from which the 'This very constant for those ca.scs where the rate of c to C mutat:ons were high and the rate of appearance of Fix are s ;rere less, Plants grown from the variegated kernels in eec? of -iS!e test t:Tpes: CcnstitutTom: centrome:Te AC ac ds- centromc~e. 4. The auuearance of . ..__ ..^ the plants with regard to Yg to yg va:yiegaticn: This a direct test for fre;-luency of breaks at c-ml, % not have to I.. - r.E$ rely on- b. cycles as with t?-e k-rnels, Each breaks eliminates2 --- Y- -~ Plant variegation Green; seldom if any yg streaks Kernel t:pe "'an:; c to C mutations; no wx areas Green; few yg streaks Green; many yg streaks verg Green;/many yg streaks. Leavily streaked. "B&h freqenclgr of c to C mutations; few ws areas Lower frequency of c to C mutations higher frequent;- of wx S?O-tS Low free-uency of c to C mutations; l::igh freal:ency of xx sT7ots 5. Concltions: , . DsC unit that alters the ratio of events Gsc,ne b:_1 -ks to those that give (1) Some change has occurred to t'ne that give c to C mutaticns r;ritl:out chr dicent.$ic formations, is DsC locus does not a?xear to have event "chat is altered in ratio of (2),The total number of events at th changed. frequency. It is ti;.e consequence of the e rise t* to these changed conditions arbse called -- changes in state of t3.e locus, (3). The alterations of DsC that giv suddently -- and only dlen AC is preset (4) o These chan,:es at the locus al-e II. The stability of the different altered s-bates of c-ml. , 1. Changes in state occur relatively frequently if tne state under cxrnside:+ation gives many dicentric c!-= at the D&Z locus, I,,omat;ids as tl:e cc::sequence of an event i3. 'They are rare if tjxerstate under consideration gives few dicentrics 3. If ihe state gives no dicentrics, state is very stable. or exceedingly few of them, the ' breaks -- that is, It does not change with regard to occurrence of -.... -- ,. dicentric chromatids, I.- _. (Emp&-+i~~e the dicentric aszz>-t) 'i" _____-Ix_... __^ . . e.-'.-' -- " .-- a). It results in a "pure') mutable gene. This . , %tis is $nportant. , quite compxable *' occur or are rare, o other kno~~rn mutable genes where breaks al;; I? rently do not b). This state of.c-ml is comparabi+e in its behavior in all major respects to the al - Dt condition, long knot.m in maize. III. The stated of Ds at its standard locztion illtxxin~~Ltec~ by the sturQT of chancres in state of c-ml, 1, The sudden change in action of Ds at its described earlier: _c . ., s-Landsrd locaticn -- fl _ Ds -. . 2. Tests m.nde of its stability: selections Quite stab&e. "ad to make very rigid among many kernels to obtain a state with increased freql:cnc;: of dicentric formatlens, 3. The increments in increase -- occurred stepwise, 4. The plants -- comparisons of variegation patterns when constitutior:s: Yg =% Ds-standard location AC ds YR c-&.b-+ AC YE? /'a l- b ,> YE? CL9 ac I Appearance of !rz-nel Apnearance of plant c $&A p$$ E &.iC k--- -7- 5. Conclusions: a). The Ds fl state reflects same co dlt-ion as at c-ml with s ate having few dicentric forming events in comparison with mutatTons to C. b). Th.e Dsfl pattern -- reflects only those events at Ds "ii-bat give rise to dicentrics. Probably as many other changes occur ac ~I,th c-19 but the result can not be id ntif'ied by a phenotq?ic alteration, as with c-d. Possibly sane XL;: cx I.d be found to detect t'nese pkeotyyic ciianees, but not an 1.Th.e test: 2. 'Ilho ear: cars, a) . "hese of stable recessives, C, from c-ml c-ml/c-ml, AC/AC (alleL5.c) female x c/c/ ad/at male Few colorless, non varie~a ed lqc~:-nels a~,-~zared On 3OXe co19d arise from changes of AC and losses of b). From changes of c-ml. to give a stable c. 3. Some of the colorless kernels selected: AC. Host resulted fromchanges of A few from changes of c-mL to give stable c, or no c to C mutat.i,ons in the tests made, The tests: Tests __ for urosence of AC -- AC tesi;er stock Crossed to c/c/ wft1: AC to test action of c-ml grossed to c/ c no AC. 4. The stable c from c-ml: a>. NO c to C mutatrions (wit::in tests m&e) when AC present, b). No diczrtric fromat ns. -- no bxaeaks at c cl. A new stable, recessive c mutant. Xuch like those stab&e a 1 mutants obtained from aI-Dt tests, -- The actir.n of AC on c-ml and Ds-standard locat9on dlen both In sane kernel, 1, The CrOssfi c-ml, 'tax ds; AC female x c Ux Ds ac male. State 0P c-ml i'igh frequency of c to C mutations NO dicc;ztrics Gi? rare. State of Ds: Hi,gg f re.:.uencF of dlcentric fez-alnations 2. The constitution of ~,o kernels: Background of kernel: cclorless aleurone; Hx in stamh of underlp.ng cells, a>. Consequence of a break at Ds -- a wx area w. Consequence of a mutaticn at c-m3 -- a C area in t;ie alaurone la:- ;r. 3. 'he genexl ap>Jearance of the kernels: 4. The ch.anges occurring soxmtically to AC to produce sectors w5th alteyed action -- l.or,:er dose p-ye or increased dosage tpe: Lower dose sector NC AC acti sect&r 5. The coincident events at c-ml and at Ds-standard: What to ex.:ect: @flat observed: colmmcidence. i=lany coincidences observed. Some without Difficulti s in mayfng exact intcrpretatinn: d . Chanps in state of Ds as consequence of thfs event. b). Translocatlons, etc, Then, instead of a dioentric forms-tion -- occur. no wx spot need be ri'ormcd, c-ml The control of AC on the time and the cells in x?:l.ch events at both and Ds at standard loca-Lion will occur: 1. 'I'he doses of AC -- and easily seen relationship, as sho';n above. 2. The resnonscs of' both to tjcle stabifized AC, C sl.2 bz wx ds ac x 1 Sh Bz $1~ i)s Stabilized AC The Trnnsposit3.:n of Ds fron t?le locus of c-x@. 1, i-iow recognized: In sectors that a7e C; in the kexels .- c/c/c-ml, AC, ac ac ik to right of C c 2 LC 0 Ds to left of C Twin-sgots B.F. f cycles: - 3 &T--r ^- I i.- 2. The oCC2zicnal ap::earance or germinal llnlt~:k;:;.or! I-;J.th Ds in new gosition: in crosses of c fernle by-c-d AC nzle, To ri,ght of c; A, ti.- To left of C Twin-spots 3. The tests Gf the qlaats derived frog t2lese kepnels: 4. Crossed to c/c ac Pema!Ses b). liernels on ear: Wm Show thrt Ds is vxqesent in G carrying C!iZi'!JXr. sczre: a)nly about 5 or 6 cascs~ emmined, Can remember the positions 0: only three of them: \J C Ds 3h for one 2.) Ds C Sn for another