6th March 196'L

Departmsnt*o* Biological Sc&ncBa,
Purdue Unfversitg,
Lefage t te I Zndfana 47907,
U&A,

Dear Sewell,

   We were very pleased to get your letter, and Sea~n the new informatio
about the position of component 301   It certainly :8eem9 that you do not
pick thfs up unless the gene fs working fafrly strongIg.   we E38EoiU.l~ fX'Olil
what you say about the expected size of the psptide'thaf yau have located
the rfght-hand end of fts prssumabfg by using amber mutants.   Sydney is
very keen that you should try the effect of a UGA mutant to tha ,rQht of
component 30.   We now have a weak suppressor fcrr UGA and so we can
always ob-hain i% wbersvsl! WB have ani ochre,   It would be I.n%eresting
to compare the effect of an cmhre aad UGA at the same 8ite to the ri.ght
of oompsnent 30.   ff you wKL let us know roughly where oomponent 30
fs S dney would be very pleased tt, produoe such a pair of mutants for
ycxz t we would probably also make the amber as well 3.e we could),   Of
cour8&) we would expect that with an ochre or an ambe there you should
ffnd a reasmabla amount of component 30, but we are not at all aleas
what to 8X&Wdi for UGA,

   As far as 1 recall the evfdence af last 8umer about the revertants
of oahrea turned out to be no good because whan Sydney looked Into
A'31and*s data the reversion rate wae far too szrmall to be signffioant,

   Bath Sydney and I would weloom %ilIiam MctCJain in elther the
summer OT fall of 1968 (it would not be possfble to have.him earlier),
so da encourage hfm to look into fellowships.   1 am asking Lealie

Contimed CI+*oC


Dr S, Chamge.

Barnett
to know

to send

6th March 1962.

you tha mutants you ask for,
pwld like ~~ornae of them1     Sydney is very 4x4..rious

F,H.CL  Crick,