I. 2easons for being asked to t2lk on rty work:

1. i:e+d genetic phenwxenon d_iscov-red in r?a.lze -- not ;;reviwsl:: noted
     in ot';?.e~ S't;-&j.(-S*

2.  I)henOmeizOn is probe 1-y quite general;  not confi-ned to lilalze.

II. The xajol> topics:

1. `he orL@n of ixany 3.utzticns.


8 kncvm ge:le.  Yhen horn0 z;,-gous,
the krnr~.m -ece s sive :

bm

          ---



--


-3-

endosn
abse&
wx s-l; c.

  i;ix to wx.  Wx rem! ts in gx:du.ction of axylose st:!rch in
e 32 2nd :olZ.en g-ah.  wx, recessive muant locus, resillts in
8 of SEC'l stnrch, amylopect5.n present.  lax skG.ns blue w!.tlrl iod:ke,
ins red,   Deficiency o:? Vx, reproduces the HX p!:e;loty-~30,

;a). &he e ssentials of t,is mechanism:
      .'..

(1) Ihe constitutfcn of' the ~?l+W;es. (&..ailS impD?tant; _
                           lxter.)      ,@ven

      9 emal e               i`L2.1e

( 2 )  The f'l: I slon of bl-o1.:en ends in tile zygote

                      / ------.., \
                  / <
               /': .+  c-l "\\

. )'

f- ._


(5) The 13, xslons of broken ends at teloy-:rise
     ,,/ y-- -----.--

`.    *..
\'     `.

(7) The repetitizhon of the cycle in the succeediy divisic.-,

       `-, c- 4I.i               L.---C-
                       
              --   __ `
                     -,      I     . .
               _.. .-

(b). In experiment,  hot:? broken ends a-t?e in si?-art aim Of chroq:Oso!:rie 9,

continuous breakage and fusion produces du?~lic-ti*~zns, deficie:?cies,
reduplic::tions and reorientations:  Zxaq3ies :

    PC).  Observation:  "he b.f',b. cycle can cease in  SC' :::e :c e ?+ 1 s .   2'rOX
then on, the broken e:?ds behzlve as normal ends.

   @I. The effects produced in the glan';s by t?Le cY-:ro,:loso:Te t: pe of
b~~e-~~~age-fusion-bridEa cycles:

(1) `he an -,e::rance of i&e :::+edlings

(2) The m~~e,crc-mce of normal a~l~~earing sectors and branches.
           _ 

     (3) The deat'h of the defective branches,  any -t-:e su:1.>vival of t!ie
normal bran&es.

v, Tne cytological examinati-.n of the c&-y-- _..osor:es i:? the normal branches:

  ?? o  The expected types of al-Lcratir:ns i- t1;e s:.:ort am of c5.r:; os?-ze 9
founcl.  &q3lic::tif?ns ?? segments, reduplic$t!.ons of seg;Xen.ts, rearraq;cnents
and deficiencies,

2). In addition, and tiis is iz.ortant, a nwlber of very unexpected t:?ees
of rearrangenenks seen.
of the co&le::lent.      T-nese involved chr: -:osor;?e 9 and otLer  6.1: i) .osc..:~e p
                                                                           L L
             &arvq
                  _ Lc n;;e::lents or_:curred at p.x?t< cula~ places in t:7-e
ChF -x2so-t71es in each case.   %ese will be considered in  et251 I.a%;or after
a discussion of the organization c'f chw:*osozes has been ,given.

VI. The procedure used to find the ex-ected new r,lutants:

  1. Each branch (about i~S0 brnncl-1s.s. nltoget+zr) self-pollin.>ted.
   Pollen (mle pAetes) placed on  si ks of sac s'iclk - Pollen 71r-)!q!
tassel placed on silks of same branch.  ii he silks le.Td to the OVU~6?8,
each 0wl.e curries a ferzrile gzlete.


  2, !Szcll err resulting frog sell?-nollination exmi3ed for ~I.J.~F~~~::IIS in
the k2mels.

VII, The Results:  General.

1, A number of new mutmts appemed, as expected,   In addr' tI.cn, a
la;,ge number of new phe2 oty:-pes, not at all expected.

%e paQtorns of stmaking seen i_n the seedl<.n,v,s:

VIII. The distrlbL:tion and frcqzency 02 c&cges in expressicn. 3xaqJ.e:
       lipj;;t green to dark preen: -                   \,
                                i                  !\
                         i                      :



          :


Sectors
Sectors
Sectors
Sectors

(33). Lie  "Twin-Secto33"

Full green-no vz.riegntion: ~Full green,reduced frequency Of s%reaks:


-70

X. The condlr~s$ons from the kitial observaticns:

               of plants that izti underbone the c. b.P.b.cycle,
1. In proGen:: derived from self-pollinations/ a Lange number of newly
proSwed altcw.%i.ons of gene loci occwred.  kn>~ 05' them (ov-T 1-1-0 L?ound>
were e>x:-esscd as va-.>iegation reselrbling "stable genes,"in tZ:eTr `behavior.
         ._
2. i n all we!.1 exaM.ned cases, a pa~t_i.cula:~ tpe of variggation r?e.ttern
                                                _.
pxqescnt in the i;eed" 'rigs.  yhe
of mut:~.tit-m obsj?Tved.       pattern -- size and f:~eir,uency 2.3 2ieli. as tJq3e

3. Charges occu:=red dw9x-g the development of the plant in cc:>tf-in cells
leading to obv?ous c'xnges i2 the time, t:-nejand frequent;: of xmtztion in
t'ne descendents of this cell,                 -

1:. `LTne a?-;?e.z-.-ance of twin-sectox>s s';o:;ed that so?eth5ng pre:;ent controllin
the pattern of xutatLon.   Tki.s could be altered as
somet-ing that occurred during a mitotic c:Tcle.    a cor!sequence of

5. Also, tie mutc.tion process itself occurred as
soxt,-lin@ that occurrrs dur5ng a titotF;c cycle.     the co:~se~~~:3nce of

  6, %erefo::e:  If mutation g-,rocess,  and if control of mutation :?yocess
in a developing leaf is rela.tecl to the mitotic process, it is subject to
expc~5mcntation,

XI, I n ilext lecture, ~5.11 take up the discovery or' the c?ww:osonal
asnects involved in t:;e c'r!sr?ge oP`ph~ot:~e
system,                             - the discover of the 3s - Xc
                                                                           B -