BASIS Independent Silicon Valley

BIOLOGY 109

1. The relative amount of in a cell at various stages of the cell cycle is shown in Figure 1 . Figure 1. Amount of per cell during different stages of the cell cycle, relative to the beginning of the stage Which of the following best describes how the amount of in the cell changes during phase? (A) The amount of doubles as the is replicated. (B) The amount of slightly increases as a result of new organelle synthesis. (C) The amount of does not change while the cell grows. (D) The amount of is halved as the cell divides into two daughter cells. 2. Antigens are foreign proteins that invade the systems of organisms. Vaccines function by stimulating an organism’s immune system to develop antibodies against a particular antigen. Developing a vaccine involves producing an antigen that can be introduced into the organism being vaccinated and which will trigger an immune response without causing the disease associated with the antigen. Certain strains of bacteria can be used to produce antigens used in vaccines. Which of the following best explains how bacteria can be genetically engineered to produce a desired antigen? AP BIOLOGY Scoring Guide Big idea 4 IST AP Biology Page 1 of 65 (A) The gene coding for the antigen can be inserted into plasmids that can be used to transform the bacteria. (B) The bacteria need to be exposed to the antigen so they can produce the antibodies. (C) The of the antigen has to be transcribed in order for the produced to be inserted into the bacteria. (D) The of the antigen has to be translated in order for the protein to be inserted into the bacteria. 3. Arsenic is a toxic element found in both aquatic and terrestrial environments. Scientists have found genes that allow bacteria to remove arsenic from their cytoplasm. Arsenic enters cells as arsenate that must be converted to arsenite to leave cells. Figure 1 provides a summary of the arsenic resistance genes found in the operons of three different bacteria. E. coli is found in environments with low arsenic levels. Herminiimonas arsenicoxydans and Ochrobactrum tritici are both found in arsenic‑rich environments. Figure 1. Operons found in three selected bacteria for arsenic removal Researchers claim that bacteria that live in environments heavily contaminated with arsenic are more efficient at processing arsenic into arsenite and removing this toxin from their cells. Justify this claim based on the evidence shown in Figure 1. (A) There are multiple operons controlling the production of proteins that process and remove arsenite from cells in both H. arsenicoxydans and O. tritici. In contrast, E. coli has only one operon devoted to arsenic removal. (B) Both H. arsenicoxydans and O. tritici contain the gene that codes for a repressor that turns on the operon to eliminate arsenite from the cell. (C) Both O. tritici and E. coli contain the gene, which codes for a protein that helps remove arsenite from the cell. (D) Both H. arsenicoxydans and O. tritici. have more arsenic resistance genes than has E. coli