Cazinge Week 6

Discovery Question Responses

1. (Question 5, p. 110) Choose two genes from Figure 4.6b (PDF of figures on Brightspace) and draw a graph to represent the change in transcription over time. Create your plot in Excel (or other program that can do plots) and display the image up on your wiki page. Alternately, you can do it by hand, scan or take a photo of the plot, and display the image on your wiki page.
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2. (Question 6b, p. 110) Look at Figure 4.7, which depicts the loss of oxygen over time and the transcriptional response of three genes. These data are the ratios of transcription for genes X, Y, and Z during the depletion of oxygen. Using the color scale from Figure 4.6, determine the color for each ratio in Figure 4.7b. (Use the nomenclature "bright green", "medium green", "dim green", "black", "dim red", "medium red", or "bright red" for your answers.)
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3. (Question 7, p. 110) Were any of the genes in Figure 4.7b transcribed similarly? If so, which ones were transcribed similarly to which ones?
   • Genes X and Y were transcribed the most similarly, they both follow the pattern (roughly), of Black -> dim red -> black -> medium green
4. (Question 9, p. 118) Why would most spots be yellow at the first time point? I.e., what is the technical reason that spots show up as yellow - where does the yellow color come from? And, what would be the biological reason that the experiment resulted in most spots being yellow?
   • The reason that the spots are yellow at the first time point is due to there being an equal ratio of green to red dye at said timepoint. Because there is an equal amount, both dyes are represented equally, and thus their colors combine. Since red and green make yellow when combined, the spots start off as yellow.
5. (Question 10, p. 118) Go to the Saccharomyces Genome Database and search for the gene TEF4; you will see it is involved in translation. Look at the time point labeled OD 3.7 in Figure 4.12, and find the TEF4 spot. Over the course of this experiment, was TEF4 induced or repressed? Hypothesize why TEF4’s change in expression was part of the cell’s response to a reduction in available glucose (i.e., the only available food).
   • TEF4 was repressed by quite a bit, given that its color is bright-green when compared to the surrounding genes.
   • As TEF4 contributes to protein synthesis, when the cell recognizes a reduction in available glucose, it likely represses TEF4, as it has few to unnecessarily spend on functions such as protein synthesis when there is a low amount of glucose available.
6. (Question, 11, p. 120) Why would TCA cycle genes be induced if the glucose supply is running out?
   • TCA cycle genes function as energy metabolism genes. When glucose is no longer readily available, TCA genes are induced in order to make energy for the cell.
7. (Question 12, p. 120) What mechanism could the genome use to ensure genes for enzymes in a common pathway are induced or repressed simultaneously?
   • Genomes should use transcription factors to ensure genes for enzymes in a common pathway are induced/repressed simultaneously.
8. (Question 13, p. 121) Consider a microarray experiment where cells deleted for the repressor TUP1 were subjected to the same experiment of a timecourse of glucose depletion where cells at t0 (plenty of glucose available) are labeled green and cells at later timepoints (glucose depleted) are labeled red. What color would you expect the spots that represented glucose-repressed genes to be in the later time points of this experiment?
   • TUP1 represses glucose-repressed genes. As TUP1 is no longer available to repress these genes, I would expect the color of their spots to be red.
9. (Question 14, p. 121) Consider a microarray experiment where cells that overexpress the transcription factor Yap1p were subjected to the same experiment of a timecourse of glucose depletion where cells at t0 (plenty of glucose available) are labeled green and cells at later timepoints (glucose depleted) are labeled red. What color would you expect the spots that represented Yap1p target genes to be in the later time points of this experiment?
   • Yap1p provides resistance to environmental stress. In an experiment of glucose depletion, the cell would undergo an environment of stress, and thus I would expect Yap1p to be induced and therefore produce red spots.
10. (Question 16, p. 121) Using the microarray data, how could you verify that you had truly deleted TUP1 or overexpressed YAP1 in the experiments described in questions 8 and 9?
    • For YAP1, if the spots are bright red after performing the experiment then it's very likely that YAP1 was induced and thus overexpressed. For TUP1, if it had truly been deleted, then it should be neither red nor green, and instead black due to no change occurring.

Acknowledgements

This week I worked with my partner Qlanners on the discovery questions segment of the homework. I mainly texted him whenever I was stuck on a problem and needed guidance.

While I worked with the people noted above, this individual journal entry was completed by me and not copied from another source.

Cazinge (talk) 00:02, 10 October 2017 (PDT)

References

1. Campbell, A.M. and Heyer, L.J. (2003), “Chapter 4: Basic Research with DNA Microarrays”, in Discovering Genomics, Proteomics, and Bioinformatics, Cold Spring Harbor Laboratory Press, pp. 107-124.
2. LMU BioDB 2017. (2017). Week 6. Retrieved October 5, 2017, from https://xmlpipedb.cs.lmu.edu/biodb/fall2017/index.php/Week_6