DSA Review Answer Key

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Evolution 1
#1 Why are internal membranes and organelles important to eukaryotic cells? Organelles isolate specific reactions increasing metabolic efficiency
#2 What was the purpose of the Miller Urey experiment? To simulate early Earth conditions as understood in the 1950s and to prove that the molecules essential to life today could have formed under early Earth conditions.
#3 Populations of a plant species have been found growing in the mountains at altitudes above 2500 meters. Populations of a plant that appears similar, with slight differences, have been found in the same mountains at altitudes below 2300 meters. What kind of data could be collected to provide a direct answer to the question, do the populations growing above 2500 meters and the populations growing below 2300 meters represent a single species? ability to cross-pollinate. ability to produce fertile offspring. DNA comparison. Comparison of chromosome number and structure. Fertile hybrid populations between.
#4 Refer to Trees: Which of the following phylogenetic trees is most consistent with the data? C
#5 Fossils of a microscopic organisms are found in rocks determined to be over 3.5 billion years old. Identify a type of evidence that could be used to answer the question of whether the organism was photosynthetic. Presence of photosynthetic structure. Oxides in surrounding rock.
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#1 Refer to Extinction: The students are sampling a side in search of fossils from the Devonian period. Based on the chart, which of the following would be the most reasonable plan for the students to follow? B
#2 Refer to finch intro: What mechanism is behind the change in beak size in the finch population? A change in gene frequencies in the finch population due to selective pressure from the environmental change.
#3 Refer to Muscle: What would be the result of continued presence of the antibody? A decrease in action potentials in the muscle, causing muscle weakness and fatigue.
#4 Refer to Anabaena: Based on your understanding of the ways in which signal transmission mediates cell function, which of the following predictions is most consistent with the information given in the diagram? A. Free calcium is needed for heterocyst formation. Binding the calcium will prevent cyst formation
#5 Refer to Spirogyra: Autotrophic algae are maintained in a water solution containing dissolved carbon dioxide and a source of phosphates but lacking nitrogen compounds. A researcher determines the rates of synthesis of several organic compounds found in the spirogyra before and after several weeks in the water solution. Which of the graphs best illustrates the likely results of the experiment? B. Without nitrogen spirogyra can't synthesize proteins or nucleic acids
Chemistry and Cells
#1 Refer to Cell Signaling: The mechanism of action of many common medications involves interfering with the normal pathways that cells use to respond to hormone signals. Which of the following best describes a drug interaction that directly interferes with a signal transduction pathway. B
#2 Refer to Phagocytic Cell: Which illustration correctly illustrates the process of pathogen digestion by a phagocytic cell? C.
#3 Refer to Red Blood Cells: Which of the following best predicts which diagrammed microscope view the laboratory worker would see? C. The saline solution is isotonic to the contents of the cell.
#4 Refer to the amino acid diagram: Which diagram correctly illustrates a dipeptide and an amino acid in the optimal position to form a tripeptide? A
#5 Refer to ARA operon: Which statement can be best used to justify why the GFP is expressed by E. coli cells after transformation with the plasmid? A. Arabinose will bind with the repressor protein allowing expression of the genes controlled by the ara regulatory sequences.
DNA and Genetics
#1 Why do retroviruses such as HIV, which have RNA as their genetic material, show a very high rate of mutation? errors are introduced in the DNA molecule through reverse transcription.
#2 Refer to Fruit Flies: Explain the difference between the expected data and the actual number observed. Chi square doesn't conform to mendelian frequencies. Body color and eye color are linked genes. Novel phenotypes are the result of crossing over.
#3 Refer to DNA: When DNA replicates, each strand of the original DNA molecule is used as a template for the synthesis of a second, complementary strand. Which of the following figures most accurately illustrates enzyme-mediated synthesis of new DNA at a replication fork? (Refer to the DNA diagram) E.
#4 In a population of certain frogs in which the allele for brown skin is dominant to the allele for green skin, a drought leads to selection against green-skinned frogs. When the drought ends, 12 percent of the remaining frogs exhibit the green-skin phenotype. If the population is now in Hardy-Weinberg equilibrium, what will be the frequency of the green-skin allele in the next generation? 0.34-0.35
#5 In a certain species of flowering plant, the purple allele P is dominant to the yellow allele p. A student performed a cross between a purple flowered plant and a yellow flowered plant. When planted, the 146 seeds that were produced from the cross matured into 87 plants with purple flowers and 59 plants with yellow flowers. Calculate the chi-squared value for the null hypothesis that the purple-flowered parent was heterozygous for the flower color gene. Give your answer to the nearest tenth. 5.3-5.4
#1 Refer to Succession: Based on the diagram, why do other trees replace oak trees following a fire? Other trees grow taller than oak trees, forming a canopy that shades the understory
#2 Refer to Prey and Predator: Use the graph to calculate the lag time in months between the change in the densities of the prey and the predator populations. 1.4-1.7 Months
#3 Refer to Carbon Flow: How much carbon is released into the atmosphere as a result of the metabolic activity of herbivores? 60 g/sq. m
#4 Refer to Population Growth: What biological factors determine the shape of the growth pattern shown for bother period 1 and period 2? Period 1: Exponential growth, lack of limiting factors, birth rate exceeds death rate. Period 2: slowing growth, density dependent limiting factors, carrying capacity
#5 Refer to Nitrate: Figure I and II show the growth of an algal species in a flask of sterilized pond water before and after the addition of phosphate. Which curve correctly predicts the algal growth if nitrate is added instead of phosphate? C. Phosphate is the limiting nutrient in aquatic ecosystems
Final Question
Refer to Hedgehog: One approach to treating patients with pancreatic cancer and other cancers in which the Hedgehog protein is detected is to modify the Hedgehog signaling pathway. Which of the options is the most useful approach? C. Inactivating Smo will modify the Hedgehog signaling pathway, thus reducing the risk of developing pancreatic cancer cells.