mglater's blog

We were interested in analyzing the water quality of the stream by the Sylvan residence halls. Research has shown that the levels and diversity of periphyton found in the water could be used as a way to analyze the overall health of the water. Periphyton is a broad term, consisting of algae, cyanobacteria, and other microscopic organisms living in the water. We created a method to collect samples of periphyton by placing three glass slides held together into the water. We placed these slides at three different locations in the stream, and collected samples after one week and after two weeks. We found that the levels of periphyton collected increased over the two weeks, and used the Shannon Index to quantify the diversity and abundance. We found that one of the three locations had a significantly higher number of total periphyton.

We were interested in analyzing the water quality of the stream by the Sylvan residence halls. We found that the levels and diversity of periphyton found in the water could be used as a way to analyze the overall health of the water. Periphyton is a broad term, consisting of algae, cyanobacteria, and other microscopic organisms living in the water. We created a method to collect samples of periphyton by placing three glass slides together in the water. We placed these slides at three different locations in the stream, and collected samples after one week and after two weeks. We found that the levels of periphyton collected increased over the two weeks, and used the Shannon Index to quantify the diversity and abundance. We found that one of the three locations had a significantly higher number of total periphyton.

As expected, the H0 yeast matings served as controls, all resulting in white colonies. The H0 strain is unmutated, so the genes complemented any mutant that they were crossed with. Both of the unknown A type mutants gave the same results, meaning they share the same mutation. When crossed with HB2, they formed a white colony, meaning the genes complement each other. This means that the mutation in the A mutants is in Ade1. This is confirmed by the fact that the cross between the unknown mutants and HB1 results in little to no cell survival. The mutations are in the same gene, and therefore cannot complement each other. The two unknown alpha mutants also gave the same cross results and are therefore the same mutation. The unknown alpha mutants complemented with HA1 to produce a white colony, while they failed to complement with HA2. Following the same logic as with the A type mutants, this means that the mutation in the alpha yeast is in Ade2. Looking at the crosses between the A and alpha unknown mutants further supports this claim. The crosses between the unknown mutants all resulted in surviving white colonies, meaning that the genes complement. The only way for the mutations to complement are if the mutations are on different genes.

The YED plate and the MV+Adenine plate do not provide information directly about whether the mutation in the yeast is Ade1 or Ade2, rather, they act as different forms of a control. The YED plate contains all the nutrients needed by the yeast to grow, but has a suboptimal amount of adenine. Because of this, the yeast cells attempt to synthesize adenine, and the mutants that build up AIR turn red. On the other hand, the colonies of yeast which are wild type or which complement each other are able to produce adenine with no buildup, and remain white (Figure 4). The appearance of red cells on this plate is a confirmation that some of the mating crosses did not have complementary genes.

After three days of incubation, the growth of yeast on each plate was unique. On the YED plate, all colonies grew very well, but some colonies were red while others were white (Figure 4). The MV+Adenine plate had all colonies grow well to a slightly lesser degree than the YED plate. The colonies on this plate were all white cells (Figure 5). The MV plate was the most drastic difference. While some colonies grew to the same degree as on the MV+Ade plate, there were colonies which were extremely weak, or completely non-existent. The colonies that were healthy were white, while the remains of sickly colonies were red (Figures 6 and 7).

Yeast were plated and each plate was mutagenized by Dr. Loomis by exposing the plate to UV radiation for 9 seconds via a UV light box. Cells that turned red were allowed to grow into larger colonies to be used for the experiment. Four different mutant strains were produced, two of mating type A and two of mating type alpha. Yeast labelled “A” were of the A mating type, while yeast labelled “B” were of the alpha mating type. A YED plate was set up in a grid to perform crosses (Figure 2). Each side consisted of one mating type of non-mutant yeast (HA0/HB0), a known Ade1 mutant (HA1/HB1), a known Ade2 mutant (HA2/HB2), and the two mutant strains for that mating type (MA1/2, MB1/2). After one day of growth, the yeast were crossed in a gridwise manner. Two days later, the yeast were replica plated to an MV plate and an MV+Adenine plate (Figure 3). After three additional days of incubation, the yeast colonies were observed. The full procedures followed for all steps can be found on Moodle.

Yeast were plated and each plate was mutagenized by Dr. Loomis by exposing the plate to UV radiation for 9 seconds via a UV light box. Cells that turned red were allowed to grow into larger colonies to be used for the experiment. Four different mutant strains were produced, two of mating type A and two of mating type alpha. Yeast labelled “A” are of the A mating type, while yeast labelled “B” are of the alpha mating type. A YED plate was set up in a grid to perform crosses (Figure 2). Each side consisted of one mating type of non-mutant yeast (HA0/HB0), a known Ade1 mutant (HA1/HB1), a known Ade2 mutant (HA2/HB2), and the two mutant strains for that mating type (MA1/2, MB1/2). After one day of growth, the yeast were crossed gridwise. Two days later, the yeast were replica plated to an MV plate and an MV+Adenine plate (Figure 3). After three additional days of incubation, the yeast colonies were observed. The full procedures followed for all steps can be found on Moodle.

The purpose of this study was to examine mutations in the yeast (Saccharomyces cerevisiae) adenine biosynthesis pathway. Adenine is one of the four nucleotides making up DNA, and thus is a vital compound for the survival of the yeast. The synthesis pathway of adenine has many steps, with different enzymes changing the compound until finally adenine is produced. The enzymes involved in these steps are named “Ade” followed by a number. This study examined mutation in the Ade1 and Ade2 enzymes. Ade2 converts the compound AIR into CAIR, and Ade1 converts CAIR into SAICAIR

To determine whether the mutation in a red yeast cell is in Ade1 or Ade2, the knowledge of complementation was used. The idea of complementation is that when two mutant haploid cells mate and produce a diploid, the ability of the diploid to produce functional, non-mutant proteins depends on whether the parent mutations were in the same gene or different genes. If the mutations were in the same gene, the diploid would inherit two dysfunctional alleles, and would therefore also be a mutant phenotype. However, if the mutations were in different genes, then the diploid would have one mutant allele and one functional allele for each of the mutant genes. The functional gene would be able to produce a functional product, and the diploid organism would not show the mutant phenotype. In this experiment, if the mutations of the haploid parents were both in Ade1 or Ade2, the diploid offspring would not have a functional copy of either enzyme, and thus still be red. If one mutation was in Ade1 and the other was in Ade2, the mutations would complement, and the diploid yeast would appear to be wild-type. Through complementation analysis, the unknown mutant gene in a red yeast colony can be determined.

Through complementation analysis, unknown mutations within the yeast (Saccharomyces cerevisiae) adenine biosynthesis pathway were identified. Studying the ability of unknown mutant colonies to produce successful colonies with known mutants revealed the identity of the unknown mutation as either a mutation in Ade1 or Ade2. Four mutant strains were examined, two strains of the A mating type and two strains of the alpha mating type. The A type yeast produced living colonies when crossed with a known Ade2 mutant as well as the unknown alpha type mutants. The alpha mutants produced living colonies when crossed with a known Ade1 mutant as well as the unknown A type. Using complementation analysis it was determined that both unknown A mutations were in the Ade1 gene and both unknown alpha mutations were in the Ade2 gene.