Auxotrophy Experiment Laboratory


BY4741
W303-1A
his – –
leu – +
met + + (partial red color)
ura – –
trp + + (red color)
ade + – (red color)
YNB-ALL + + (partial red color)
YPD + +
MATa + +

Discussion:

Genotypes of BY4741 are MATa his3Δ1 leu2Δ0 met15Δ0 ura3Δ0. (1)According to this, we need to see no change in the petri dishes where these materials are not available. We should have any change in cultures having no these material, because mutated yeast cells, BY4741cannot produce essential growth nutrients without presence of these materials. His, leu, met and ura are auxotroph for the cells. Except “met”, the results are like we expect. Only the culture “met” shows positive result. During placing cells onto plate respectively, we placed “met” nutrient into the dish having to have lack of “met” accidently because of bad sterilizing. Other possibility is contamination during experiment by hands, or a wrong movement od experimenter.
Genotypes of W303-1A are MATa ade2-1, ura3-1, his3-11, trp1-1, leu2-3, leu2-112, can1-100. (2) W303-1A cells are formed mutated for these growth factors. Without these nutrients, culture can’t grow. Ade, ura, his, trp and leu are auxotroph for the cells. In this experiment, we shouldn’t have seen growth at “trp” and “leu”. The result show that these strains were prepared wrong. Also we saw red color at some samples. We see white colony if no change exist on the genes affecting pigment producing pathway. The reason of red color is that any mutation on ade2 or ade1 occur a change at adenine biosynthetic pathway and this accumulation form cell-limited red pigment. (3) . Without “ade” dish, we wasn’t expecting. Best explanation is contamination.

References:
http://www.yeastgenome.org/strain/BY4741/overview
http://yeastgenome.org/strain/W303-1A/overview
Agnese Kokina, Juris Kibilds, Janis Liepins. 1 August 2014. Adenine auxotrophy – be aware: some effects of adenine auxotrophy in Saccharomyces cerevisiae strain W303-1A. 697-707

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