Question regarding yeast strain with ura3-52 mutation - (Mar/07/2013 )

I am working with a yeast strain that contains (among other mutations/deletions) a ura3-52 mutation which should result in a uracil auxotroph. However, these cells seem to grow very well in synthetic yeast medium lacking uracil. Does anyone have an explanation for this? Thanks.

The easiest explanation would be there is contamination. I would re-streak to isolation and try again. If this was a stock culture it could have gotten contaminated along the way. The only other explanation would be that the mutation is not present.