February 8, 195k ; . whe oe 7 . m-1 The mechanism of transyositicn of Ds; Origin and behavior of ¢ ae IL. Review of previovs discussion 1. Transpositicns of Ds to positicns in short arm of chromosone 9 between the known merkers: Y : AD ie BY . a), Xecovered cases -- nositions of Ds non-random, Pldnie, Eo Sis peli b). The aberrant kernels with transpositions -- wrinkled endosperms3 dead embryos, ec). the lack of germinaticn of about of the selections, it d). The dominant letheis or semi-~letuals. -- To be discussed later, 3. The changed states of Ds: One case discussed: The Ds ~ f.l. trve. a). Origin in one step from regular Dg -- many breaks, b). Occurs only when Ac presente ce). From time of occurrence, sugsests one of the conseauences of changes occurring to Ds, d).tieturn to former stete -- occurs only through successive steps, Must- select carefully, Ds - f.1., a rele atively stable state, e). The meaning of this state will become apparent when the muteble e-pl, derived from insertion of Ds at © is disuussed, It is not that changes are absent at Ds but that they do not lead to dicentri formations, f). These states imoortant in understanding the nature of mutation at the mutable loci, ~~ Wat DS pase? © ab witer foabvr , wand oF Cp taced aed porabed. @ Lx py ave II. the mechanism responsible for the transpositions of Ds, Pp 1, “eans of anrreciating what the mechanism me be came from study of several cases in which a durlicstion occurred at the time of transposition of Ds. These ccses will be discussed, 2. First case -~ A kernel showing breaks between + and Sh as well as breaks eliminating I Sh Bz and Wx wore seen ina Single kernel in cross of: Female C sh bz wx, ds ac x male I Sh Bz Wx Ds Ac C sh bez wx ds ac The ear: I kernels CG kernels 5 ad I sh Wx, non=-var, 59 pF Py C sh bz wx 128 IvSh Wx, var. BT Que © Ish bz wx non-var. 5 C Sh Bz Wx non-var, 2 shh Is:: by wx, var. 0 C Sh Bz Wx var, 5 Lae I Sh bz wx var, 0 C sh Br Wx non-var, 1 CG sh Bz wx, var. 0 I Sh Bz(and few bz) wx nonevar, 52 CG sh bz Wx nonevar, 31 T Sh Bz wx var, . 0 C sh bz Wx var, Ce Odds: 1 I Sh Wx kernel with vattern of. ar. suggesting breaks between I and Sh as well as to right of Wx, wx a I/kernel with C Bz areas. Spontaneous breakage type; not investigate 3. Plant grown from odd kernel in greenhouso,. Matured very early. Uad to be s#lf-pollinated and could not be crossed -- no plants readye 4, The kernel tyves on ear -- 18 different classes, Obviously something unusual about the ! Sh Bz Wx carrying chrmoscomes?: 178 with I: 96 wth & 168 with Wx : 106 with wx. Variegation patterns -~- sevoral times, Suggested duvlication present, S. The 13 different tyres of kernels grown in field in following summer, Cytological and genetical analysis made of the plants in each of the sub- cultures. Crosses made with each, “ests continued the following summer, The results showed that the male gamete contributed by the parent carrying I Sh Bz Wx Ds / © sh bz wx ds in the first cross carried a chromosome 9 with a durlicstion as follows: oh TOshe, we un Rs) Db ve +--+ fn see pe Se a) IV. Case II dw lication: 1. Found in cross the subsequent summer, Cross the same tyre as in above cases C sh bz wx ds ac female x I Sh Bz Wx Ds Ac C sh bz wx ds ac 2. Analysis of tris ease showed: Duplicat on in tandem order, Ds to left of I, pi Yo LShh wy 0, F2hB We” ‘ . em Adee ~~ 4 pe ee sat V. Analysis of the ~ossible origin of duplication and transposition of Ds, 1. Required conditions in both cases: a). Duplication arose from breaks in sister chromatids: In the I Sh Bz Wx Ds chromatid, This Show b: com-osition of markers in each duplicated segment, Dept Coes = nventad nat wih We ch Ry ~ os Gres = Tandon TD. Wek rh Rely p b). Case I: Must have break in both sister chromatids to left of Ds, at least, to get duplication order(breaks 1 and 2), and one break in one chromatid (break 3), In this case, Ds inserted dn the sister chromatid at the position oomparable to break (3) 1 1 BY To ohBy hoe D fo er rath see ene cae oe ee ee en ne ee ee cy ; Sanne > . Lc By Voto 7t s WAY “ue e: pa vm =e © c), Case II: Must have break in sister chromatids to right of Ds (breaks 1 amd) and to left of I in one chrematid (break 2). Ds in one chromatid must be moved to positicn comparable to break (Q) in sister chromatid, Tshk lee B® 7 2 cemencmermeel ce wenn Aenean tment ete wok = ‘ @ 2 Sn By twee OD / a” iL ae Ka tt. ® ee ee werd ear oO rch BR ' n k Ww + R VI, How ean all of this be accormlished by one tyne of event rather than the coincideng event of transposition of one Ds to position corresponding with break in sister chromatid (peal $)9 The evidence from the two cases suggest that the transyositi n phenomenon and the break vositions are related and the exnression of one type of initial situation asm ciated with Ds action. 1. Ye lmow: Ds, as we heve been following it, produces many dicentric chromatids at the locus where it may be. How does this ocuur? 2. Ds associated with the origin of translocations between chro-osones: These seen on a number of occaaions, Therefore, Ds can produce the conditions leading to breakage and fusion, 3. A possible mechanism that accomplishes the transpositions and the chroiosomal abnormalities: Associated with the state of Ds that produces dicentric formation, This important to keap in mind, (Diagr-ms on board, pares lia and lib). VI. The origin of cen, 1. In discussion of transposition of Ds, menticned those cases where Ds inserted between markers, Will now discuss those cases where it is inserted at or adjacent to a known genetic factor, First case detected was that of insertion of Ds at the C locus, 2. The first detected case, Peculiar variegation patt=srn in cross of: yg ¢ sn wx ds ac female x Yg C Sh wx Ds Ac male, Yg C Sh wx Ds ac 3. One male used in crosses to 10 di. ferent females of given constitution: a). On ear, 1 : 1 ratio of CSh, non-var, to C to ¢ var. with exception of single kernel, Photo of ear, Plas DO b). The pattern of variegation: Colored background with colorless areas. of the usual type. No color in the colorless Areas, ~ Various tynes of patterns of losses of C in the different sectors on Barnel. - c), Among a total of 359),kernels, all as expected except one. ‘The pattern of veriegation on this kernel: colorless background with colored areas? a . “ ~ No colorless areas in Colored / r | eo. APCLSe , d). Plant grown from this kernel - culture h2oh. Apnearance of plant: Many small streaks of yg. Ds-break tyne pattern: Concluded i Ds in the Sh wx chromosone, Ab ee : ‘a phd e), Plant crossed in various ways to test for subseavent anpmearance of peculiar variegation; for Ac; for Ds, The tests: To c sh Bz Wx; C sh bz Wx; Self-pollinateds; to and by Ac-tester, to pyd c Wx / ye ec Wx. f). The avpearance of the kernels in the croses toc sh: 9 ears, — 23 full colored Sh 509 colorless to colored var, Shs 725 colorless Sh 15 w "! a nt " shg 153 i sh a AW Uys) Morus & 3 Cy Valores > AWE dh\ch ’ (2) bare & | _ Ue Ue tes é a) Crane purgp Ubowerere, bine (Doluglrealin . Oo loeoute burs wut Q povben wu oly 9 behuwen E+ Sh! Cnn “Wan so 2422 ‘ue hu pee oil eM (io nl . Che rr. the GH Miu of Govt Coby Ly Br we Brye Wrbrsh Ble pan 4 2, Wt ane iguana yon honlle wa arto Ubauahior . EH %rlbe ks Os . Hy hous. Pgutian ¢ baal % U0 lu plrea tay greens oF 0, nPaculled paula ¥ af qoulua 4 Uamtur 4 Dr breeual oT Au jouehay ¥; 1 rege Fue wo eal Te et ar ane Emr ee nano eneneen (1). Conclude that muteble e locus present, (2). The miable ec (designated cml) appeared in a single tested gamete of the C Sh wx Ds/C Sh wx Ds Ac/ac grand=arent, his shown by the linkage with Sh, (8). Only 4 of the Sh kernels show variegation -- suggests requiremen of an activator. for mutations to OCCU". (l.). Ac present from tests of 420 in Ac/ac constitution, Not linked to factors on c-ml1 CHPOMOSOME, (5). Types of variegated kernels on self-pollinated ear suggested the activator dosase behevior like that of Ac, . (6). Ds present,in the c-ml Sh wx chromosome but not to right of wx, probably; this snown in tests to C sh bz , Variegation in the Sh class and almost no sh kernels were verlerateds Important: None of the 23 kernels that were C showed any © to c variega- LON. This would be expected if Ds weve present and also Ac, Also, very few of the C areas in the kernels with ¢ to C variegation showed any © to ¢ variegation, Ds activity certainly present; This clear in the plant variegation and also in the variegation produced in the crosses to bronzes Question: Where is Ds; what is happening to it when a mutation occurs to GC? a : a a VII, “he subsequent tests -- a very large numb-r of them, Only an outline will be given of the important tests for our PUPPOSeS, lelests of plants derived from the ce to © Wx kernels in crosses of original plant to females ¢ sh Wx ds ac, a). Constitution: ceml Sh wx [Ac c sh Wx | se b). Plants tested for Ac -- in all cases, Ac present, ¢). Crosses to e sh wx plants: Ratios of variegation of ¢ to ¢ those expected if ec-ml is Ac controlled, ad). The crossovers: ce-ml sh Wx and cml Sh Wx, The variegated kernels: Ds prescnt. Sectos of wx present in the colorless areas in kernel, The C areas were WE amen) % Clot ute tk aad Cu tee LS hag = The non-variegated kernels: ec Sh Wx : None shoed any Wx to wx variegation The ¢ sh Wx kernels: None sh owed any Wx to wx var, e). Ds must be at or close to the ceml locus as only the ec to C var. kernels show presence of Ds type activity. 2. Tests of the colorless Bh Wx class in same cross as above: a). Hajority expected to give plants thet are: ce=ml Sh wx c sh Wx b). All plants crossed to ¢ sh wx ds ac plants: No variegated kernels appeared on ear, either for ce to C or for Wx to wx, probably no Ac, c). Plants crossed to c sh fe sh Ac/Ac (allelic) plants, (hb) “early all kernels in Sh class showed c to © variegation, d). Tested for Ac, All plants giving ¢ to C in cross to ¢ sh Ae vlants had no Ac, e). This and other tests established the Ac control of mutability at ceml, 35 The response of ec=ml to Ac doses: exactly like that of Ds, VIII, The Ds type activity at cml, 1, Above tests show that breaks occur at or close to the ceml locus as well as mutations to C, Be Cytological evidence obtained for breaks occurring at known rosition of the ¢ locus in plants carrying c=ml and Ac, 3. Yeml arose in plant homozygous for Ds at standerd location: C Sh wx Ds / C Sh we Ds; Ac/ac lg There was no Dg at the standard Location in =lLant arising from the original e-nl carrhying kernel, This shown by tests of this c-ml Sh wx chromosome in a number of individuals, 5. Ceml arose ina gamete that had lost Ds from its standard location, 6, Activity appears at locus of C=-ml concommitant with origin of mabable ec 2 from a previously normal C, Both types of events,omutation to C, and breakage occur at this locus, 7. When mutation to C occurs, all Ds type activity ceases at the locus of the mutated CG, 8. Conclusion: the mutable ec arose from transposition of Ds to C LOCUS. the mutations arise from removal of Ds from tris locus, Therefore, ceml, being Ds at C, is Ac controlled, Ds at the C locus -- CDS ~~ ig e in activity. fhe recessive e very stable if Ac absent, Test of over 20,000 kernels obtained from crosses of ceml/e no Ac toe no Ac, ~ 7 @ VIII, Tests for the svablility of the muiatkdnC from c-ml, 1. Tests of the C kernels arising from germinal mutations: In crosses of c-ml to ec in presence of Ac, Plants grown from them; Sself-pollinated: crossed to ¢ ds ac 3 crossed to ¢ ds Ac; tested for presence of Ac. In all cases ( over 30 examined), the C is stable; 2. Tests of a few cases (rare) in woich Ds activity present in the © carrying chromosone, _ Some - a new transposition of Ds, in another -osition in short arm of enrsmosone 9, In several cases, Ds still very close to the mitated locus, IX, Before other tests with c-ml considered, must examine the states of ceml, and the changes in state, 1, The original state of ceml: Hany breaks at e-ml locus; relatively few mutations to C, 2. the appearance of sectors with changed relationships on the kernels? Ao Constitutions: c-ml / ce /e /; Ac. ac ac aoe s between 3. The appearance of kernels with various altered relationship c-ml, frequency of mutation to © and frequency of breaks at . , wh . yea tet OO” : waee’s Po eee | eae aod : ae, ee ‘ ~ gy Z ~ ‘ . * . ¢ a es ° ° ¢ ee % 4. The tests conducted with the various kornelss The high rate of ce to C mutations and low rates of breaks or none wil l be used as example, Tests -= Stability in subsecuent generations, 5, The relation of the states of c-ml to those of Ds at other rnositionss a). Indicates that the Ds-f.1,. is like a ceml with high rates of mutation to C and low breakarates, therefore, the Ds in the cases of Ds-fl is actually undergoing some change in many cells but these do not show as breaks in the chromosomes. In the case of cH y we see the other trpe of event as a mutation, In the casss where no muvation can be seen, we can observe only the breaks, These a small fraction of the alterations occurring at Ds, however, X, The similerity of responses of c=ml and of Ds to changes of Ac, 1. Comperisons between c-ml with few or no breaks and Ds in standard location with many breaks, 2. The response to states of Ac == exanrmle; Stabilized Ac, a). The pat-ern produced by stabilized Ac in cross of C sh bz wx ds ac female x I Sh Bz Wx Ds Acestabilized (Photo) b). The pattern of c to C mutations in crosses of: e fc no Ac female x ceml Stabilized Ac -- the very same. 3. Ressonses to changes in Ac occuring during development: The tyne of cross? wx Wx female c-ml/ c-ml Ac x male ce Wx Ds, no Ac: The kernels: t™ ay /t¥™g,/] ¢8 Wedo, Re Reon Speckled pattern aanerh tan, Wet Sectoria .Ls in speckled hkornel (sbouin€ Ay Wag zeke * af ?F . wt . \ a, ol! S. pet ~ | “ ef Gy “ud fa \ | roa | lL. The cottncident changes at c=ml and at Dsestandard i “these ker rnelse a i gh GbR hey Se pA a th Psat . os Rost acer wm Rho Mow , ae Pant ‘ Bee g oS \, Pique at feta od th begs | \ € abe i i So » angen “Wt: ‘lo eg Charron ab" . . | [Cour Lowel Dy vata a) iol Mos a, loa. gt Uke, Ni 0, h-l ds 6 rg Hin Ard a An ce F + ‘Ny Chu B/C Shay Re of _ the C Shey Sh EShay Und A Otley | 2. the tap or By — aiuone publia, Cover wo C7. ts Poe nos on sce Ta OD arawe , lars. Ds Gyio 1 Vortad fa hes Rela Comhtubin - 2 Cumedts i dWe ane (kd; Lpdre, by tater, @. 3, We Dowd on ear fu Yen le esnk — ly tay, wa Sh olen, ma decl. 23 CG — ash ash 125 Sh 524 22Cw. 7. 2.17 Cabalbnn ‘ sal : 3% \ Luss. i OY Vo eign ys Ue C ante, = Wo Can. dane” : Re. a) a am ae Mby- VO oe £,\ hy e dh Webs so \ tb a b) ft Acthte = Wo be (. 3te Cv) CY fo ele? fe] Ae = naw sale a, A). the drage dul wv ¢ Kee Ihe = Pork aunt ols Le = ah. patlow ce * ec Have ihe = Avery Laut ofth sent Coe fed ©) Wtertntg — te be dtnGuked Lalo, . @ 5. Tot fir pouon 4 Ds . 6.\ “5c Sh Wry high i Mir | ong au : Au tla [ada b ca We | Laut = Aum Gb ag ASA Wk \. PRewt fem Cipe Qunadl 2h on Ch yay, fee C), We Cum- ar Lew - com hl zwiSh Uy, 6 Ofperovey hou + \. Ry wn- vor Ayo a eptortor , won-var. Lava : lt be 2 SU, Wp blows City Way ce van, El, Ub bobo ob C Lew, rn yn pata 24 ty as dos 5 he Lob b,thoo , Wy C2 a Covngau Gb. tho OB Uri dr a1 abel oy 4 mo! Ta) Fur chet - ralioa an @ er Wor. oy Oe &\ Yu aodon - C\ Pho hornet, vowh Olly obec, 8) The tag 7 plouit, fre Tay Maul 4 the eballby | abelnes 71-1 a Hane abo Sa f ') Cabrdins Vrarne — pgwuersh . \ Veledinke + 2) Sone Pw te; fees = Ate eo fow oT Wolregd