生物學(xué)留學(xué)生essay代寫-Yeast genetics problems: Advanced Genetics

  1. You now cross one of the Leu- Tyr- progeny by strain ww-45 from Beth Jones’s lab that has no auxotrophic mutations in it. You obtain the following tetrads.

  a. What is the major change in the segregation patterns in this second cross?

  b. What is your hypothesis?

  c. If you cross a Leu+ Tyr- spore from the one tetrad in the second group http://www.400190.com/Thesis_Tips/lxslwfy/ (the class with 17 examples) to the other Leu+Tyr- spore in the same tetrad (assuming the mating-type alleles will allow this), what does your hypothesis predict will appear in 100 tetrads?

  d. What molecular experiments (not sequencing) would you propose to identify this change in segregation?

  2. In many fungi, tetrads are linear. http://www.400190.com/Essay_Writing/2611.html Don Hawthorne, an old yeast geneticist in Seattle, found a Saccharomyces strain in a jar of mayo that gave linear tetrads. Looking at the linear tetrads below, decide if pink and pseudohyphal growth are linked or unlinked and the distance for both genes to their respective centromeres. 46 45 4 5 Only the order within the linear tetrad is important. As an illustration, the two tetrads below would be placed in one group, as the information that they provide is equivalent. Now you isolate a new mutation that causes pseudohyphal growth (phd?);http://www.400190.com/thesis_sample/  this mutant shows greater filamentous growth than the phd1 mutant above. You cross phd? by the mutant strain above (pink, phd1). The diploids that you recover produce colonies that look like this:

  a. What are two hypotheses that explain the phenotype of the diploid with respect to color and filamentous/pseudohyphal growth?

  b. To begin to test your two hypotheses, you examine linear tetrads of from a cross of pink x phd?, beige. Are pink and pseudohyphal growth linked or unlinked and what are the distances for the phd? gene to its centromere? 70 5 5 4 6 5 4

  c. Which hypothesis does the tetrad data above support? d. Explain how you would go about cloning the phd? gene.

  3. The pseudohyphal phenotype is observed in response to nitrogen starvation. Activated Ras2 (G19V) stimulates pseudohyphal growth in strain Sigma 234 but inhibits it in a second strain. Briefly present three experiments using the power of yeast genetics and molecular genetics that may help to explain this difference.