Beadle and Tatum investigated the capability of Neurospora crassa to grow on a different medium. They did this by growing Neurospora cells in media whose composition was controlled by them. They found out that Neurospora cells can grow in the minimal medium, whose composition is only made from sugar, salts, and biotin. Furthermore, they created a mutant of the Neurospora through UV exposure and took samples of its descendants. Upon growing in the "complete" and "minimal" mediums, a few colonies survived in the "complete" medium but could not grow in the "minimal" medium. Which of the following can explain this result?