[Yeast] ade2-1 strain color

[Ren MIAO]

hi, I just received a W303 based strain from one of our collaborator. When I 
received it, it was streaked on a plate labeled with YPGal (there is a 
essential gene under Gal promoter) and was white or a little bit yellow.
I made stocks out of it and streaked some YPGal plates from the stocks. The 
colonies I got were mostly pink or red, few of them were white/yellow.
To my knowledge, ade2-1 mutant should appear pink/red due to red pigment 
formation. But I am just wondering how the cells on the collaborator plate 
(also YPGal plate) appear white.
Can I add some adenine to the media to repress the in vivo biosynthesis of 
adenine in yeast?

Thanks in advance!!

Ray

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