Continua-t. ion of discussion of wx-ml;  the &hd&etion of mutability

at selected loci;   the StZtCS Of a p3.

I. Review of previous discussion:
  1. The C locus - the origin of c-m2 from C in plants having AC,
2. The types of mutations occurring, at c-m2:

   Class I: produces substance 1 in excess and substance 2.  Color
va ies from very faint to quite dark - a spectrum of mu-Gntions in tYG.s class.
Possibly tile snectrum reflects &ount of subst,znce 2 produced.

    Class II. Produces substance 2 in excess but substance 1 ma:? l.e limited
in those Gazes qhere color is light.

    Some mutants - plent;;: of both substance 1 and subtance 2.   These
give rise to cells with exceedinglg dark pigmentat?. n -- as groat as that
produced by the normal C locus in 5 to 6 doses.

   The normal C losus -- seems to produce insufficient amounts of s?bst.?nce 1
This may be the explanaticn of Z::.e quantitative expreesi;n of dosages.

   The :wfilui;:it:fins -- those cas:-,s r-rh.e:?e ch.z1ge occurs at the c-m2
locus but gives insufficient color to be readily detected in kf:rnel.
Detection cc:mes from obscrvs.Lions of effects nrcduced on adjacent sector
whcr:e visj.'?;le -.-:;u:;;iti.cn present,

  II. The difZ'&rences bcizren c-ml and c-m2 quite obvious.   c-ml  -I-: 27 0 ti.-m e s

&  only muI.ations to the normal C t:;pe.   Only once has a small sector on a
  single kernel shown a mutat-icn resembling that of calss I above and many
  thousands of kernels shoxinp mutations of c-ml have been examined.
    If the units at the C locus -- pi_esuma:;ly D s in tl~c cnse of c-ml, and
  somet:ling similar in tile cas'. of c-m2, -- T,JQ:C tl;e same in thc txo cases,
   we should expect to f:ind some c-m2 like rlutzt5.::ns arising from c-ml by,;
  some cY?;anze in ds i;17~i; wouJ_d sir&late or replace the former action.   'his is
  not observed.
     Why do the two mu-table C loci - c-ml and c-m2 diz'f'er in t Leir er;r,:ession?
  What is controlling the expression of the gexic m::terial wLxn a change occurs
  at the locus,  unde;-, the influence of AC?

  III, %e tyr)e s of chan,ge s t?lzt have been examined at the C locus:
     (1) - c-ml from C-    AC controlled

(2) - c-m2 from C     AC controlled

   (3) c-m& from C      AC control!ed.   'i'h 5 s  c a s e  w'->.e F. it first nn:~c'r cd
gsve mutnti ns t5a-i; reserrbled t.%ose prodxxed by c-ml st:ites that, s3ow
high fror!uencies of mutation to C and no breaks.
   (4)   c-3.  'his &rose from a normal u locus.
xhe -ii:-pes of mu;at?ons:                         It is not   AC contro11ei
                 two only
a pale producing mutant       a) to the normal C e~xssion; b) to
                -- the sane pale color in all cases.

T'ne recessives:  ?fitilo- t AC
           %e kn    -- c-ml, c-?Q, c-mL~ are all stable recessives.
                    obrn recessive - c

color in the pr:sence of a f~tor -- Blotch -- - is also capable of sl~or-:i.;~g
                                    located in chrome so-,e 6
by Dr. B.A.Emerson,   The color 7-reduced very clearly dir':`-rs from t::at
given by mutati~xs oi' c-ml, c-m2, c-m3 or c-mJ+.


  The co,mmon component of all these cases is -- a change at one positTon
,i,n the short arm of c%ronoso?ne 9 -- corr:s~~onds wit:; the ti locus.
lhe changes in all cases affect the production of pigment in l&e aleurone
layer of the kernel,

   This indicates that t?ere ic so--et-.? ng at  t :-is locus in the cYro._71i> sc::-3e
t'nat is associ ted wit ~ t:le development of pigment.   Its mode of action,
in t`:is resl3ect, however, can be controlled quite differently.  Q2.i s  shown
by the differences in the expressions of tilis pigment in the cases described.
   1Jha-t is the nature of tis control?  hhat kinds of changes occur that
restit in suecific tJy3es of g6ni.c action?
   Pessibly some answers to these questions can be had in examining the
origin of other mutable ,gcn~s, and tee behavior of known recessives to
influences on tzhem.   The case of wx-ml will il?-ustrate this.

IV.   The origin of wx-ml -- previously discussed:

1, wx-ml was present in a single gamete among many t:,ousands observed
that we:ae derived from plants carr:Ting c-m2 Sh I;?x and AC,

  2. This mutable locus -- proved to ?e AC controlled.
  3. The time and the cells in rj_:ich mutat'ons will occur -- like all ot1ler
AC controlled mutable genes, -- it responds to doses of AC, states of AC,
changes in states or doses
AC-controlled mu-'iables,   occurring somatically in the same manner as other
              TU.s tlroves by combinations of them in the
same kernel -- like the cases of combinations of c-ma! and Ds, previously
described.

4. The t.. nes of mutations occurring at XX-ml:   A quantitative s;:.ries,
from a very small amount of amylose to the maximum amount observed in
normal material.

Continue with outline, page 4, February 18 discussion,

The inducfition of Ac-controlled mutability at selected loci.

I, From above discussions of orig:ins and similarites of mutable loci
derived from particular plants carrying known mutable genes, one should
be able to predict the origin of new mutable Tenes and t!&ir behavior,

  a>.  If we assume that c-ml, c-m2, bz-ml, wx-m-l, 5,5,7,8, c-m,!+.; arose
from insertion of some ccntrolling material at the locus of thegene.   If
we know that t-.is controlling illsterial can be trans?os-d from one location
to another, then:

    (1) In plants c rr-ing both Ds and Bc,
occur to various loci, among them,           transuosition of Ds could
   (2) L3y setting u?r, the    the locus of a kr&m gene,
after they occur,         --roper test ccndit?ons, such insertions,
            should be detectible,

II. The nature of the tests contiucted:
%ilot " eq3eriment as the freouency    Tine original test made as a
                       of occurrence of transposition of Ds to
a particular locus i3nt known.  The orig:nal test was small and no cntrols
were done,


  1. 'he nature of t5e pi&ot eqeriment:
  a). Number of plants carrying Al Sh2 / A 1 Sh2 in chro:scso~e 3 and
A2 Bm / A Bm
one cBrono~onel~ in chromosome 5 short arm grown.   Each :-lant had Ds in
           long arm and AC at an unknown location in the ch??-losome
com,lement:

b). Pollen from two sourses used on these plants:

(1)  al sh2   No AC;  neither recessive mutates in presence of AC


                                 !I          I1             11        :1     t1        11 11

(2) a2 bml I1 '

2, The results:

   a) 72 ears from cross (1).  All kernels with normal appearing aleurone
color except 1,  This kernel showed co$orless background &th colored spots,

   b). 120 ezrs from cross (2).
of three.                 All kernels normal in color with exception
      These three found on thrr:e different ears.   %cch &owed a
colorless background with colored spots or areas,

3. Tne tests of the single kernel from cross (1).   It proved to ::e a
mutable gene -- designated a,-&.+.   It was AC controlled.- Manner of
control exactly like that of all other AC-controlled mutables examined;

   4.  Without AC -- corn-?letPl;; coloress, stable.
   b).  kii.tn AC:   mu-tat-ons
color,                 of two main t:yyes:  pale color, and full A?
      The differences in exp;:esslon of these two classes 0~' mutants:

     Pale
No diffusion rims

Full Al
Diffusion rims

4. PIutations in $lle plants -- similar;  will be considered sho:,tly,

   d) . The germinal mutat!.t?ns
sectors.  'p&z; @-@R,.       -- like the mutaticns in k-;mels to give

   4. The changes in state:  ?ew charyes in state noted,
appeared on several occasions:                    %e type
full AC type -- diffusfon rims,  colorless with only a few small spots of the
     Tnc meaning of chani;i: s
presented shortly in       in state at the mutable al locus will be
         the examination of al-mj, anot?ier Ac-controlled mutable.


- 1.L -

4. The tests of the three variegated karnels from cross (2).

a>  The female parent:

A?

Bml n                Ds Pr

             A3     Bxl, h             ds pr
                                          v
     b 1.  ?he t::ree kernels removed, plants grol*rn from them. Tests
conducted to deterz4ne t3e nature of t5-e instability e,xpressed in the kernels.
     (1) One plant:  In the tests of this plant, the chrom;c::;o~e 5
contributed by the female parent was not transmitted to the fol'or;b :?g
generations.  SometlZng wrong :-;lith it.
'i'his mutable condit!.on lost, tlierefore,   No cytolop;ical exazinati!:n made.

      (2) Plant 2:   Prmved to have a new mutable a  locus.   Fkl5.S
arose +n the 382 Dml carrg?ng chrc~lrsome.   In t3.s plan $ , sonthing wrong
at the Pr locus or close to it -- not male trflnsmissible,    The crossovers
recovered -0 carried a2-& Dml ds pr,
        (4.
expression the same a$-*: Brmved to be AC controlled, and again t%s
                   s t3a t  sho;gn for all other &-controlled mu-Lzble  loci
with respect to time of occurrence of mute-t+-ns as an exl:,I-aesslon of AC dose
and state.   The nature of the mutat?ons -- many very pale mutations, few
like full A2 76th diffusion rfms:

The range of pales -- very light to q:aite dark; no diffusion 12Ffls.   i?POEl
frequencies obszrved in this initLa1 s&ate, many hidden mutat4.ons sus'3ccted.
They do not give any perceptible amounts of color.

     (3) Plant 3:  A nBw origin of mutability at A2 in the A2 Bml
chromosome.   This mutable is not Ac-controlled.  ijesigna,ted a2-m3.
It mutable beb.avior vcr;: different from that of the AC-controlled types,
Many of the muto.tions to full A2 ex:-:?ess:i.on and some to pales of varying
intensrty.
stable a2.  IIany earl:7 occurln,r_: :riut:.ti.ons in t3e plant; many chanr:es to
       Piany chances in state occur,
develo9ment of -r:~lant.              and these take -place enrj.:: in

states.   Can be     Plants may be I-6g::I.v sectorial for many c'-lan,yed
           exj-zcted from these plants anci xJ:*~tained as altered s2ate se

           i~lt!lou;;L: test is small, and no control, it Lc. clear
    Ac-controlled mutable iOCf may be obtained and at loci nreviously
selected for tl+.s,   The ;ncc~~ nism of control can be enticincted- but   the

tymes of mutati.ons that :,&II occur can not be antlcinzted. ~ tL'hisxll be
shown in t3.e exa.minat:i.on of aI-m3, an Ac-controli.ed mutable locus de3ved
from a normal Al in plant car:::j.nh Ds and AC,


I.  The ori@.n of Al-123.

    Con stitutiiln of pMk.nt:

   Crossed to al/al plant:    d:qo:red $jlat the locus iEvolved :ms Al
    Bo mut2hles ?3rezent at t`-is locus in sis.,cix y-lants,
II. The subceaucnt~ tests:   Thi s new nut ebie >>roved to he AC-controlled,
'lhe emrcssion or" mutati.ons dicfered markedl-ffrom t !osc of  a
described,                        i-rd> just
  1, i%ust be emphasized:  The time ol" occurrence of mutatl;onn cor*:plet~ly
controlled by Acarld its dose and state,   The $ pe of mutat'ons controlled
by cozdbtic;ns J uresent at the al-m3 J.ocus.

  2. 'he or2f 1-?aJ- s";,zte :
Spots or -:zlm s, each    R~.thc~~ dc.rlr pale bzckground with vey deep Al
               s2~:oG.n~ dif-r^%us j.on rim.

III. The types ol' states:   See chart.

IV. Summary:

1, Origin of al-33 in Al/Al 73h.M.
plant carried 0s m c:i-lm.:oscxe 1 and AC One o_" the A loci affected.
                   in unknown $occ.tim.       'L'i-l i s