The yeast Gal4 transcription activator comprises two domains: a DNA binding domain and an activation domain. The DNA-binding domain allows Gal4 to bind to appropriate DNA sequences located near genes that are required for metabolism of the sugar galactose. The activation domain binds to components of the transcriptional machinery (including RNA polymerase), attracting them to the promoter, so the regulated genes can be turned on. In the absence of Gal4, the galactose genes cannot be turned on. When Gal4 is expressed normally, the genes can be maximally activated. When Gal4 is massively overexpressed, however, the galactose genes are turned off. Choose correct explanation for this regulation?

A. In order for Gal4 to work properly, the DNA-bound Gal4 recruits many proteins, including RNA polymerase, to the promoter.

B. When there is too much Gal4 in the cell, the free and DNA-bound Gal4 will compete for the limited quantities of these other components.

C. In the presence of excess Gal4, those components are tied up in unproductive complexes with free Gal4, thereby preventing their recruitment to the promoter.

D. cells that massively overexpress Gal4 grow poorly because of the reduced availability of critical components of the transcription machinery.

E. Over concentration of Gal4 prevent suppressors to bind with DNA

#Question id: 389

#Unit 1. Molecules and their Interaction Relevant to Biology

A weak acid HA has a pKa of 5.0.  If 1.0 mol of this acid and 0.1 mol of NaOH were dissolved in one liter of water, what would the final pH be?

#Question id: 390

#Unit 1. Molecules and their Interaction Relevant to Biology

What are the properties arising due to varying concentrations of solute in a given solvent, irrespective of the nature of solute with respect to the solvent?

#Question id: 391

#Unit 1. Molecules and their Interaction Relevant to Biology

In a hospital laboratory, a 10.0 mL sample of gastric juice, obtained several hours after a meal, was titrated with 0.1 M NaOH to neutrality; 7.2 mL of NaOH was required. The patient’s stomach contained no ingested food or drink, thus assume that no buffers were present. What was the pH of the gastric juice?

#Question id: 393

#Unit 1. Molecules and their Interaction Relevant to Biology

Carbon dioxide (CO2) is readily soluble in water, according to the equation CO2 + H2O ↔ H2CO3. Carbonic acid (H2CO3) is a weak acid. If CO2 is bubbled into a beaker containing pure, freshly distilled water, which of the following graphs correctly describes the results?

#Question id: 400

#Unit 1. Molecules and their Interaction Relevant to Biology

Consider two solutions: solution X has a pH of 4; solution Y has a pH of 7. From this information, we can reasonably conclude that ________.

#Question id: 401

#Unit 1. Molecules and their Interaction Relevant to Biology

.Which of the following graphs describes the relationship between [H3O+] and pH?