>When I put this strain (Which is ade3, his7) through a cross
>Histidine auxotrophy segregated mostly 3:1, indicating that in addition to
>the his7 allele another mutation affecting His-ness was segregating -
>could this be sap3?
I just wanted to let everybody know that didn't already know:
ade3 mutants are phenotypically His- !
The reason for this is somewhat unclear although it may be that
precursors of THF or tetrahydrofolate (the product of Ade3p or THF synthase)
may somehow be poisoning enzyme(s) in the histidine biosynthetic pathway.
THF itself is not required for His biosynthesis although a related
compound tetrahydrobiopterin is.
The reason that His- was segregating strangely for Lenore was
that ade3 was also segregating along with his7. As to sap3 I have never
heard of it. Good luck!
Department of Biochemistry SJ-70
University of Washington
Seattle, WA 98195
moser at u.washington.edu