The mcchani sm of transpositicn of Ds;  Origin and behavior of c m-l

It, Review of previol:s discussion:

  1. Transpositicns of Ds to posit'.::ns in sho-zt arm of chr~~osorle 9 betT:ecn
the kncwn mrrkers:

*: _ a).  iiecovered csscs -- zositi~ns of Ds non-random, l%-&i,& , gy&u;, ts d.
                   ~ ,.~:&*
b).                      8
     The aberrant kernels with tranq-:ositirjns
      dead embryos.                 --. wrinkled endosperms;
  CL The lack of gerdnaticn of about & of the selections.
  d) . The dc>itinant letheas or semi-let-:als. -- To be discussed later,
3. The changed states of Ds:   One case discussed:  The Ds - f.1. tye.
  4. Origin in one step from regular Ds -- many breaks.
b).  Occurs only when AC present.

CL From time of occurrence, suggests one of t:?e consenuences of
         chanps occu-rrin~; to Ds.                         
                         .1

ci),ri-eturn to former state -- occurs only t:zrou& successi-:e s%ens.   alst
   select carefully, Ds - f.l,, a relatively stable state,-
4. T'ne meaning of this St&e will become aqF:arent when the mu.tnble c-w,
   derived from 73
           -,,::s-rtion of Ds at c is discussed.   It is not that
   changes are absent at 2s but that they do not ILead to dicentric
   fomaticlls.

  2. First case -- A kernel showin& breaks bettieen ' and Sh as well as brenks
eliminating I Sh Bz and Wx w2re seen in a single kc:-nel in cross of:
    Female C sh bz wx, ds ac x m&.e  I Sh Bz Xx Ds     AC
                               C sh br: wx ds       8C

                The ear:
       I kernels                        C kernels

  I Sh Wx, non-var. 59
   I:,Sh Wx, var.
1 .,

C sh bz wx 128

I sh bz wx non-var. 5
I s.: bz wx, var.     0

I Sh bi wx var.     0


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I Sh Bz(and few bz) wx non-vzr.   52    C sh bz 1;Jx non-var. 31
I Sh Bz wx var.          .            0     C sb bz T;dx var
                                                           i              .     22

Odds: 1 I Sh Xx kernel with pattern of  ar. suggesting breaks between
         I and Sh as well as to right of Wx.
  I/grnel with C Bz areas.                                       d
                    Spontaneous breakage type; not investigate

3. Plant grown from odd kernel in greenhouse.   &&ped vcq- ezT;?ly, ITa:!
   to be s&W-pollinated and could not be crossed -- no plants ready.

4. The kernel types on ear --
    unusual about the 1   18 di:ffeFcnt classes,  Obviously something
                  Sh Bz Wx carrying chrmos'::,?es:

178 with I : 96 d th c;
168 with 'Yx : 106 with wx.

       Variegation patterns -- seTJ':ral tT3es.   Suggested du:~lication
present.

5. The 13 different ty:>es of kernels gra>m in field in following summer.
Cytological and genetical anal-To
cultures.             .)-is mac:e ofr,th.e plants in each of the sub-
           Crosses made with ez::h.   *ests continued the f'ollor.~ri~g
Sumner.  The results &owed that the male gamete contributed by the ::arent
carrying I Sh Bz t/x Ds / C sh bz wx ds in the first  cross carried a chromosome
9 with a duplic-tion as follows:

IV. Case II dulication:

1, Found in cross the subsequent summer,  Cross the same t:TTe as  in above
case:

C sh bz wx ds ac female x I Sh Bz Xx Ds    AC
                   C sh bz wx ds  8c

2. Analysis of t 13-s case showed:
    left of I,            Duplicat- on in tandem order, Ds to


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V. AnalysSs of the --ossible origfn of dqlicctinn and transposit?m or Ds,

1, Reouimd ccnditions in both cases:

a). Duplicatbx arose from breaks in sister chrmratids: In the
   I Sh Bz irJx Ds c3roxatid.   This sl-iol-mb: con-ositi on of markers
   in each duplicated se,went',

               \\  i' be D : 1 ih!iL%t~ st@Q LQ+gJJ I+3?$$ E ,
     b), Case I:   Hust have break in both sister chromctids to left of
  at least, to get duplication orderibrenks 1 and 21, and one break in one Ds,
chroxatid (bz-eak 3).   In this case,  Bs inserted &n the sister chromatid
at the positim oomparab2.e to b?erIy, (3) 1 i
             `t       L
              `I ' ibV&      l*.- c 0,
                       --._I  --.----I-__ _.. . .  L .--. -_.~ _~--      t
              _-^___- .___--- -
           `It ";h'Ij;,        _.               .o
                          LL,b
, `/       L   d     9
I>                    5-l       &I
                     -I   5 LLR,    `\th Q-A             c

   d.  Case II:  Duct 'nave b;.-eak in sister ch?oxatids to right of Ds
(breaks 1 ,M) and to Left of' I in one c?m-z&id (bx-eak a).   Ds in one
chroxa'iid muzt be moved to _nositic n coq?a~ab!_e to break (a) in slstcr c?~.rcz,?l;id,
              -l.gtbl    ia+. b.d@.J
                      . ..-1. --- --. - -. _.--.. A+

VI. Iior~ can all of t;~is bc accomlZshed bg o:le ty-c-!e of event rather -tIan
the coinciden& event of transposition of'
with break in sister ch-onatid (b%&a-tr"'5)? one Ds to pos?tion corresponding
                                 The evidence I"ron t&e two cases
suggest that the transposlti n phe:.loxenon and t3.e break rcsitlons are
related and the eqression of one ty?e oi" initial situation as~ciated 515th
Ds action.
  1, :le know:  lk, as we have been followi2~ it
chrozmtids at the l.ocus t?nme it may be.      , produces many dicentric
                                 How does t&is ocuur?

2, Ds associated w2t,?1 -the oTigiz of translocatZons  between cl~x~~oso.+-ms:
These seen on a number of occaalons.
leading to breakage and fus!.on.     merefore, Ds can nyoduce the corxEt?ons
3. A possible mechanism that accox:llishes the  t mns~ositlons  and the
chro ::?oso-real abnomalities:   Associated with the state 03 Ds that ~rodv.ccs
dicentric formation,   This important to Beap in mind,

(Di.a,q.-m on board, pases l&a and hb).


VI.  Tlhe origin of c-ml,

1. In discussLon o.f t:>anspositicm of Ds, rncntioned those czszs wh.ez;e
Ds inserted betraeen m~~rkcrs.   I-Till now discuss those cases where Zt is
inserted at 01' adjacent to a known genetic factor.    3irst case detected
was t&t of insertion of Ds at the C locus.

2, The first detects?d case.  PeculSar vericgatlcn pa':t;-;rn in cross Of:

yg c sh wx ds ac female x Yg C Sh wx DS    AC
            YgCSnwxDs ac   male.

3. One male used in crosses to 10 dLferent femles of given constitution:

a>. On ear, 1 : 1 ratio of CSh, non-vu. to C to c var. witn exception of
  single kernel,   Photo of ear, PMl@

b), The pattern of variegation:
     of the usual type.    Colored background with colorless areas.
                        No coloi? in the colorless Areas,
                      Various t:nes of patterns of losses of C
          *                  in the diffe:-ent set-to?ps on karnel.

  CL  Among a total of 3594,kernels, all as expected except one.   !IThe
pattnm of variegation on this kernel:  colorleks background with colored
areas:

No colorless amas in Colored
areas.

d) .  Plant grown f~on this kcxel - culture ,!.4.%0!~.  Appea-ance oi' ??lant:

Hany small streaks of yg.  Ds-break tyF?e pattern:   Concluded
         c          Ds in the Sh wx chrc?:Iosome.
        i \
        'i 1 \

        : L.

       : i  :i
       i  i

  4. Plant crossed in various ways to test for subsequent ap':earance of
peculiar variegation; for AC; for Ds.   The tests:

      To c sh Bz Wx;   C sh bz 'Jx;  Self-pollinated; to and by Ac-tes+:er.
      to pyd c Ux / yg c Xx.

f). The appearance of the kernels in &he croses to c sh:  9 ears,

       23 full colored Sh
      509 colorless to colored var.
       15 "      ,I2 II         Shs
                                                11        725 colorless Sh
                                sht  1453 "      sh

     ,. ' ,   >
     _
       ,k   't 'L i .


\ '
        /"

---7   / \ . . .
          `;"\

+



I~~*  Conclude that mut:nble c locus present.
    .  The mutable c (designated c-ml) appeared in a single tested
   B amete
       his  of the C Sh wx Ds/C Sh wx Ds Ac/ac grand--arent,
        shown by the lir&age with Sh.

(j). Only Q of  t' ne Sh kernels show variegation -- suggests requiremen
     of an activator. for mutations to occur.

(4). AC present from tests of 4204 in Ac/ac constitution. Uot li-zked
      to factors on c-ml c~:~~mso171e.

    (5). Types of variegated kernels OE self-pollinated ear suggested
         the activator dosage behavior like that of AC,        .

    (6).  Ds present,in tke c-ml Sh wx chro:::osoine but not to right of wx,
          probably;   this sIlown in tests to C sh bz    Variegation
      in the Sh class and almost no sh kernels weie variegated,
Iqortant:
     tlon, None of the 23 kernels that were C showed any C to c va-iega-
        This would be e,vectsd if Ds wetie present and also AC,
    Also, very few of the C areas in the kernels with c to C variegation
    showed any (3 to c variegation,

          Ds activity certainly p-escnt;   This clear in the plant
variegation and also in the wariegation produced in tl:o crosses to bronze.

            Question:
mutation occurs to C?     Where is Ds;  p?fiat is happening to it when a

VII, Ahe subsequent tests -- a very lnrge nmb-:r of them.
will be given of the important tests for our puqoscs,     Only an outline

1,Tests of plants derived from the c to c' &h Wx kernels in crosses of
       original plant to fenales c sh Wx ds ac.

4.  Constitution:  c-ml Sh      wx

                      C    sh     WX
b), plats tested for AC -- in all car;zs, AC pres-cnt,

c). Crosses to c sh wx plants:   Ratios of vcriegaticn of c to C
   those expected if c-ml is Ac controlled.

d), The crossovers:   c-ml sh Wx and c-ml Sh Wx*

The variegated kernels:   Ds present,  Sectos of wx eresent in

The non-variegated
  variegatio+

kernels:  c Sh Wx :  lij-one shoed any Wx to wx

              lhe c sh Mx kernels: None &owed any bJx to wx var.
4. DS ,mst be at or close to the c-ml locus as onlp the C to c K-r. honeys
     show presence of Ds tyi?e activity.


2, Tests of the colorless EXh 1x class in same cross as above:

a>.  lVlajority expected to give plants tnat  are :

c-ml Sh wx

                probably no AC.
            sh  WX
b). All plants crossed to c sh wx ds ac slants*  110 variegated kc:rnels
  ap:>eared on ear, either for c to '6 or fir Vx to wx.

4. Plants crossed to c sh / c sh  AC/AC (allelic) plants.
  (a) ii early all kernels in Sh class showed c to C variegation0

d)O Tested for AC,
  had no AC.    All plants giving c to C in cross to c sh AC slants


4. This and other tests established the AC control of mutability at C-d6

3. The response of c-ml to AC doses:   exactly like that of Ds.

VIII,  The Ds type activity at c-ml..

  1, Above tests show that breaks occur at or close to the c-ml locus as
well as mutations to C,

the a. Cytological evidence obtained for breaks occurring at kno~m ,.
  c locus in plants carrying c-ml and AC,                   73osition of

3. &ml arose in plant homozygous for Ds at standard loc<ztion:

c Sh wx Ds / c Sh = Ds;  Ac/ac

4. There was no Ds at the standard location in --plant arising from
   the original c-ml car+lying kernel,  This shown by tests of this
   c-ml Sh wx chr:,::;osome in a number of individuals,

50 c-ml arose in a gamete that had lost Ds from its standard location,
6, Activity anpears at locus of c-ml concomrnitent with origin of mtibable c
  from a previously normal C.
  breakage occur at this locus,  Both types of events,cmutation to C, and

7. Xhen mutation to C occurs,
  the mutated C,       all Ds type activity ceases at the locus of

8.  Conclusion:  the mutable c arose from transposition of Ds to C locus.
   the mut&tions arise from removal of Ds from tis locus,
    Therefore, c-ml, being Ds at C, is AC controlled.

Ds at the C locus --  CDS -- is c in activity.

'Ehe recessive c very stable if AC absent.  Test of over 20,000
   kernels obtained from crosses of c-ml/c no AC to c no AC,


VIII.  Tests for the stability of the mutzt&cInC from c-ml,

1, Tests of the C kezmels arri.sing f~omgez$nal mutnt?ons:
    In crosses of c-ml to c in presence of AC,

Plants grown from them;   Self-pollinated; crossed to c ds ac;
   crossed to c ds AC; tested for presence of AC,

Pn all cases ( over 30 examined), the C is stable;

2, Tests of a few cases (rare) in w?.ich Ds actLvity present in the c
     carrying chrorzosome.
   some - a new transposit?.on of Ds,   In another -:ositfon in she+
      arm of chr~:oso~e 9.
  In sevemzl cases, Ds still veF[ cl.ose to the mutated locus.

IL  Before otiher tests with c-ml considered, must examine the states of c-ml,
     and the changes in state*

1, The original state of c-ml:
    few mutations to C,     "'any breaks at c-ml. locus; relatively

2. The appearance of sectors with changed relatlcns5ips on the kcrnelst

Constitutions:  c-rriL ,' c / c /; AC. ac ac

                                     /.   ,:;\--       * i .:
                                     ',
                                       *'I t,*,; -\  '2.b
                                                    '   :
          ,e$ A--

3. The appcazance of kernels with various altered relationships between
    frequency of mutation to C and frequency of breeks at c-nil.

4. The tests conducted with the various kernels:   The high rate of c to c
   rilutat?cns and 101~ rates of breaks or none will be used as exa:zple,

Tests --

Stability in subsequent generatinns:


-8-

5. The relation of t'ne states of c-15 to those or Ds at ot3.9~ cositlons:
                                                                           _~

    4. Indicates that the Ds-f.1, is like a c-ml rifith high :%tes of
mutaticn to C and low breakarates.   Therefore,  the Ds in t'ne cas?s of
Ds-fl is actually undergoing some change in many cells but t'nese do not show
as breaks in the chromosomes*  In the case of c-giL, we see the other type of
event as a mutation.  In tLle cas-s t;ihere no mu-Lation can be seen, we can
observe only the breaks.   These a small fraction of the alterations occurring
at Ds, however,

X. The similarity of responses of c-ml and of Ds to changes of AC,

1, Compnrisons betrreen c-ml :;'itIn few or no breaks and Ds in standard
locatlcn 3fith many breaks.

2, The response to states of AC -- example; Stabilized AC.

a). The pnt.:ern produced by stabilized AC in cross of

         C sh bz wx ds ac female x 1 Sh Bz `l-ix 0s  AC-stabilized (Photo)

b). Tne pattern o:? c to C mutatZons in crosses of:
     c/c  no AC fem=ile  x c-ml  StabTlized AC  -- the rey,: Eame.

3. Hes.:on.ses to changes in AC occuring durjng development:   The ty>e of
     cross:

female c-ml?c-ml AC x     ' Mx Ds, no AC:

The kernels:  p+,q //p&J &3~b; tAcJlz+~
Speckled pattern           Sectorials in speckled i:c:.nel

                                                                        I . ..-I
4. The co3tncident changes at c-ml and at Ds-standard i:i tllesc kernels.


c \