Gene Expression and Regulation

7.a) Based on the data provided, identify the gene that is most likely to encode a protein that is an essential component of glycolysis. Provide reasoning to support your identification.

7.b) The researcher observed that tissues with a high level of gene H mRNA did not always have gene H protein. Provide reasoning to explain how tissues with high gene H mRNA levels can have no gene H protein.

6.a) Based on the data, modified cap II is most likely to protect the end of the mRNAs from degradation because it has the longest mRNA half-life.

6.b) Based on the data for the mRNAs with modified caps, there is a positive relationship between the mRNA half-life and the total amount of protein produced. As the mRNA half-life increases, the total amount of protein produced also increases.

6.c) The researchers' hypothesis is not supported by the data. Although the mRNA with modified cap I has a similar half-life to the mRNA with the normal GTP cap, it produces significantly more protein. This suggests that each mRNA molecule with modified cap I is translated more frequently than each mRNA molecule with the normal GTP cap.

6.d) The production of a foreign protein may be more likely from the introduction of mRNA than DNA into cells because mRNA is directly translated into protein in the cytoplasm, whereas DNA must first be transcribed into mRNA in the nucleus before being translated. This means that the process of protein production from mRNA is more direct and faster than from DNA.

1.a) Circle ONE arrow that represents transcription on the template pathway. Identify the molecule that would be absent if enzyme YUC is nonfunctional.

1.b) Predict how the deletion of one base pair in the fourth codon of the coding region of gene Trp-T would most likely affect the production of IAA. Justify your prediction.

1.c) Explain one feedback mechanism by which a cell could prevent production of too much IAA without limiting I3PA production.

1.d) Rhizobacteria are a group of bacteria that live in nodules on plant roots. Rhizobacteria can produce IAA and convert atmospheric nitrogen into forms that can be used by plants. Plants release carbon-containing molecules into the nodules. Based on this information, identify the most likely ecological relationship between plants and rhizobacteria. Describe ONE advantage to the bacteria of producing IAA.

1.e) A researcher removed a plant nodule and identified several “cheater” rhizobacteria that do not produce IAA or fix nitrogen. Describe the evolutionary advantage of being a bacterial cheater in a population composed predominantly of noncheater bacteria. Plants can adjust the amount of carbon-containing molecules released into nodules in response to the amount of nitrogen fixed in the nodule. Predict the change in the bacterial population that would cause the plant to reduce the amount of carbon-containing molecules provided to the nodule.

1. Describe the effect that the addition of a charged phosphate group can have on a protein that would cause the protein to become inactive. Explain how a signal can be amplified during signal transduction in a pathway such as the PHO signaling pathway.

2. Based on Table 1, identify a dependent variable in the researchers’ experiment. Justify the researchers’ using the wild-type strain for the creation of the mutant strains. Justify the researchers’ using mutant strains in which only a single component of the pathway was mutated in each strain.

3. Based on the data in Table 1, identify the yeast strain and growth conditions that lead to the highest relative amount of PHO1 mRNA. Calculate the percent change in APase activity in wild-type yeast cells in a high-Pi environment compared with that of wild-type cells in a low-Pi environment.

4. In a follow-up experiment, researchers created a strain of yeast with a mutation that resulted in a nonfunctional Pho85 protein. Based on Figure 1, predict the effects of this mutation on PHO1 expression in the mutant strain in a high-Pi environment. Provide reasoning to justify your prediction.