Continuation of tranqositicn of Ac;an d its relzticn to soma%ic sectoring and to controls of mutaticn of mutable genes. I. Review of previous discussion: 1.173 all major respects, AC is inherited as a mendelian unit: a). Expected statistical ratio in F2, a AC : 1 ac; found. b). Expected 111 ?I in b.c. #of AC/W: 1 : L; fo: nd. 2. When)bomozygote, revealed: AC/AC, beckcrossed by ac, some unexpected events ? o Not all of the plants carry AC -- few with no AC b). Others, 2 AC fac%ors, independently located I~ % -t-he 4. Alteration in action of ActCLDWd: h (1) Dosage action of single AC double that of original AC = kFoL (2) Dosa& action of single AC increased over that of original AC but not double that of it. (3) Dosage action decreased. Ds breaks occur earlger in develoxment of tissue than those occurring when orif;inal was present. 3. The changes in AC occur la+e in development 0:' the sporogenors tissues: (1) This shown by the scattg,ed kernels on ear tnat carry the changed AC factors. (2) In case presented, !a - the ovules these changes occurred in only a few of produced by the fe:rlale plants, II. ihat is the mechanism responsible for t3cse changes of AC? 1. If one AC transposed from one chroimosoze to another in sporogenous cell, before meiosis, could get either no AC or 2 AC in the resul.t?ng apore or gamete: Fb- AL Q`py&i r fh.- k ,l; 2 (kc Qc.i P p&,,&&L i$ - -- 4 - -- -- !h.c i p&Jy - -- ,> (. $..q,j 2. If one AC in one cb?_rc;ycsc:;e redupllcatin, remains in one Ch`iT'C~Yl~e~SO:re af tcr ChrcposC-;.e can ret double-dose AC or no AC: In develocment 0:` the mepasnore but not both: either of these two cells recovered OriL;~ one cell-p: into the megas~ork~' -and onely one of spores produces the female gametorhyte: 3e In either case, wo:.ld ex-.:ec.L to fi,-;d a 1 : 1 ratio of kernels with no AC to those with eithe- 2 AC or docLble-dose AC. Observed: 19 with no AC to 23 witl eitl:er 2 AC or,ATAc I 4. In addition, AC was found to change Ln action-- to increase its dosqe action or to decrease it. How does this occur? :kb I J? If it is transposed, does its ;;Nositicn affect its action? If channes occur of this ty;3e, without chancge in nositicn, is AC ccm?yosed of a numbsr of sub-units? C'r, is its efficiency in scme manner eatered? III. What evidence i!?aT-e we that AC doss move from one ositicn to anot',lcr in the chromosoxal ccm lemcnt? To study, sho: ld know t?:e position of AC in the chro?ioscme corn lement and study is changes at t5is position and its removal from this T?ositi n, This was done because of atqecrance of AC in chrc:?oso-ne 9, which is well marked. 1. The first discovered case of AC Appearance in cb,rc:~osoxe 9: a). In@Gross of ac/ac plant by Ac/ac plant, no evidence found for any 41ink::l-e of AC with marke-:s in cI?rom~~some 9. b) The F '?~&-ing AC grown. 9 ulan* . 1 A*: * L bs crossed to Plants not carraying AC. h Both cl->roL-Tosomes 9 in male pa::ents with AC carried genetic markers in chrcxcsoxe 9, CL 8 plants showed th,at AC was not lir:_ked to factors in ch&---oso--e 9. d). 1 plant; the AC in t?l.s plant linked to markers in Cr. 9. 4. Its position tested, Found to be located to right of Wx: c xx Ds AC f). Type of data obtained in test of linked and non-linked AC: C sh bz wx ds, ac female by I: I Sh Bz llrx Ds AC male b Sh Bz wx Ds ac II: I Sh Bz I-iTx Ds e AC C Sh Bz wx Ds 8C Table 1, pc-ge 23, Symposium >aper. 0 , -39 2, Later, other cases of ap-earance of AC in chro-;-tosome 9 found. One of them, AC in short arm, just to left of Nx: C AC Mx Ds a> b axample of how such a case discovered: Mumber of ::lants in a culture came from one in t:r ich AC had not been located in chro::1osorre 9, These slants tested for AC. in &roxoso;-ne 9: One among them may now show AC Female: c k?x AC X C wx Ds, ac male: CWX -is- cernels on resupltkng ear: kJfdQ +-ikG 1 C Vx, non.v-riegatcd : 1 g Wx, with az=eas bk of c wx 1 C wx, non-variegated : 1 C wx, with areas of c bh-- la. If female were c AC Fix x C wx Ds ac, then, modified c ac wx ratios of variegated to non-verieg- cted classes: exnected in Xx and wx The ex$ent of deviation from 1 : 1 would depend upon how close AC were to Wx. And, the frequency of transposition of AC from &rot-:oso:Te -position, as indicated, to another-: position, Example in one test: c wx c:&lss --- Non-var. CWx-cwx var C wx class PTon-var. Cwx with c areas 19 207 164 14 b). AC obviously closely linked to \$x. '?he order could be: (1) or (2) c AC Wx c blx AC C ac wx c wx ac :). In usualy genetic test, three-point test: it would be simple to locate factor by a C AC Wx C ac \wx ~~e~eim,i.ne th e ?ositrion and crossover fresuencies readily in most genetic tests. 'his not easy in the case of AC, This is because of transpositions. d). A numbor of different tszts conducted wit? tis case, it took nearly three years before location and cross-over frequencies could be stated with some certelr:ty, 4. Tests are tedious to describe and not easy to follow because of number of genetic markiers used; and the many ty-pesbf' tests made. f), To avoid4 such descrinticns, a relatively simple type of test can be used to illustrate what happend: The cross: female male (1) c ac6aids c ac (WX)ds Y C ac &&Ds C Ac%xcds (2) Type of kernels on the resulting ear;:, 'heir constitutions as expected: 478 Colored, non-varieg,ated : non-crossovers cross-QVBT C ac Ds 6~ C AC ds CT ac Ds c as ds c ac ds c ac ds 17 Colored with c areas C AC Ds c ac ds (3) 17 "crossover" carrying kernels selected from ear. Plants groom from them. 16 plants tested; one died. Eac~lqSai~n;O~.e~~sB~d~,b~~r 1 Wx Ds ac I : tr to c wx ds ac The results: 13 plants of 15 only, as records of other 3 not here: 6 plants were crossover types: 6 plants had AC, but not in chrolr;osorne 9 short arm (4). This test shows th,at only half of the apnaeent crossovers are true crossovers. 9 short arm. The rest carry an Ac, not in cb.ro:~osorre 4. Other cases of appearance of AC in short arm of chroly,osome 9: AC C WX a. Changes in AC that were observed: Disapgearance from short arm coincident with a:Inearance elsew%re. Change in dosage actions Increased or decreased, either xith or : without change in location. --... ,.,;. +p, \ >,.&. , : L,-' 1 t !?E? - 5. A correlation noted between changes j,n location, and/or action of AC and changes occurring at Ds. 'he coincidence rr:te is high. a). This has made it nossible for ready selections of changes in location of AC- in kernels carrying them. Will be discussed later, where tllis will be strikingly a?xa:Te'7t. IV. With evidence of changes that occur to AC in mind, it is possible to evaluate t'ne patterns produced in kernels carrying Ds and AC. 1, The "early sectorials". of kernel. Changes of AC occur very early in development Result in sectors showin 'These ap;-Iear in kernels carr:-ing two B different types of AC action: c or a double-dose AC, Female witn AC LLale wi th dc-1-ibFdo se AC c sh bz xx ds AC x male 1 Sh Bz Xx Ds no *&c C sh bz wx ds m I+etcDs ac AEAC The endosperms: 2 independent AC 'he endosperms: 1 AcAc e 2, One of the AcAc males (homo2ygous and allelic positi_ons) crossed to various tester plants as females. 90 - 95 $ of kernels we e early sectorials: c /c "j. .f s r,, ' l The 3 most frequent types: - 7- The infrequent Q-pes: Sk- 3. Other cases, from crosses with female introducing AC. Some isolates give sectoring later in develonnent: sxamples: l+il4@@ W', 4. b31i.tl:. t?is in mind, 1 AC present. can attempt to evaluate the patterns observed when Examples: a). The kernels are mosaics of different AC constltuti*:ns: No AC -- not Ds breaks; sectors not sliowing breaks $0 ,2A= - sectors produced wfth late occurring Ds brep.ks sub "ittBZn them,/sectors produced with no Ds breaks or later occuring Ds breaks. b). Pattern of variegation in the kernels receiving 1 AC reflects the changes occurring to Ac and the time of these changes. It is not a "chance" pattern of Ds breaks. 3 - c>J Different isolates of AC can show quite different patterns in 1 dose. (1) Yit3 some, changes in AC commence early in the development of the endospeum. (2) With others, these OCCUT mch later. ($1 The ccnsequence: Various t.nes of patterns produced by different AC isolates These different actions reflect differences in the kc facto;s These differences have been designated different "states" of ---"-a-- AC, S -..- V, The bearing of the AC investigation on the problem of what control the mutations at tne locus of the mutable genes. is operating to 1, In the first discussion of this series, the reasons for study of mutable loci were emphasized, undertaking the were many, - - 2. It was em>hasized that in all examined cases,'-and there a controlling system was present. This system controlled the time of occurrence of mutatiens dur?ng the develoy?ect of a tissue and the cells In w%ch it would occur. (5). Whe- e did tL1i.s AC come from? If we assume transposition from short arm of chro:qosom.e 9 to another chrozoscme, this situation could be ex-olained: 4. C AC ds C ac Ds . . . . . . . . . c-e........ b). homoioguis homologues of anothsr chromosome AC transposed in this cell to ,*...... chro:losone: C ac ds C ac Ds . AC . ..*. ?? o ? ? ? ? ? ? 4 *'*eTotic segregations: Synapsis: Segregations: C dc ds ac ..*...**. C ac Ds AC . . ...*..*. Spo@genous cell C ac ds .-- C ac Ds . . . ac ,*****.***4 . . . . . . . . . . . AC (6). In the described test, in selecting fo r sup;7osed crossovers, -?y$ we are also selecting for transpositions of Ds. &x'I1 were present in approximately one-half of the supposedly cross-over class. yk -7 3. ?Je can also test for the removal of AC from chrn osC:~.le 9 &ort arm: a>. Exawle 02 the type of test: Female Gale c AC x C Ds ac c AC C Ds ac Types of kernels on ear from one such test: (Host of tests not here), 6 C, non-vnriegated: 3 kernels did not germinate 168 C with c yeas: 3 remaQ:ing plants tested: $hLf l 2 had ng AC 2 kexnels with very 1 had AcAc but no change in locat$t L- ii a_ ,*I late speckled patter of losses. s Plant grown from one of two kernels: 2, AC not in chrczosome 9. Plant I was : C Ds L AC c ds x6- AC action altered from that shown w?:en in chr. 9, -80 3. The observations for these conclusions came from the ap;Jearance of "twin sectors". They were: 4. ThBse relationships within the twin sugqested that one cell received sometX.ng that tile other cell lost, --- and t-?is something was associated * G7 with the control of mutations in future development 1. in the cells arising from those where the c.%nges occurred. 5. Since twin sectors ayn.ocr to come from sister cells, the event anTeared to be associated wit!: the mitotic process. 6. Also, the mutation -orocess itself a)::e::Ted to occur duri.ng a mitosis, and n the controlling s;-s-I;em: 7. AC controls bhe occurrence of breaks at Ds. If these events at Ds are compared to the mutations at mutable loci, then parallels mav be drawn: AC is the controlling system controlling the %utaticns" in this case. a). Segregations of AC occur at somatic mitosis. One cell can gain an AC that txe other cell loses. Restit is an altered time of occurrence or the absence of occurrence of Ds breaks in the progeny of the two resulting cells: b). The concident changes at both AC and Ds: Result in sister cells, these frequent. one of which may hzve altered AC: Change in AC in b-Z sector witin Ds break , ,i e-------- -_--- -5!L- -- J iiesulting sector: CL The parall.el regflrdlng controlling systems is striking. This wo?Cid suggest that the mu:;::ble genes also hzve controlling units that a-e responsible for the patterns of mutations. These un%ts either at the locus concerned or are separate - as Gth Ace VI. In next discussion, wol!ld like to consider Ds again and s+ow that it, also, transposesf'tiomone location to another and that there are very strBing consequences produced as a result of this; It is the cause of the a--;t:,earance of some of the mutable genes.