和咱们国内的竞赛一样，同学们如果能在这些竞赛中拿到好成绩，那么也就意味着距离名校又进了一步！接下来，顶试留学想和大家聊聊的是USABO竞赛的含金量如何以及部分USABO竞赛真题，如果你也对USABO竞赛感兴趣的话，希望下面的内容可以帮到你！

　　一、USABO竞赛的含金量如何？
　　USABO竞赛的含金量如何？如下是顶试留学为大家整理的信息：
　　学术性强，影响力大
　　USABO竞赛作为美国理工科竞赛中的重要项目，以其比较高难度的真题设置和广泛的影响力，成为了数以万计想提高生物水平和申请国外名校的学生的选择。
　　据不完全统计，每年有超过2万名的美国高中生参与USABO竞赛，而在国内这一趋势也日益明显。
　　申请名校的助推器
　　USABO竞赛的获奖证书和参赛经历，不仅是学生生物学术能力的有力证明，更是他们通往顶尖名校的一把金钥匙。
　　这些荣誉和经历，在申请大学时能够为学生增添不少光彩，增加其被心仪学府录取的几率，尤其是哈佛大学、斯坦福大学、耶鲁大学、康奈尔大学等藤校非常看重USABO奖项。
　　培养生物兴趣，提高生物水平
　　参加USABO竞赛，对于学生来说，不仅是可以学习到更广泛的生物知识，更是一次对生物学科深入了解和培养兴趣的过程。
　　通过参加USABO竞赛，学生能够更加系统地掌握生物知识体系，激发对生物学习的浓厚兴趣和持续热情，尤其是想选择医学、生物学等专业的学生。

　　二、部分USABO竞赛真题
　　Streptomycin is an antibiotic that works by binding to the 16S rRNA, preventing protein synthesis from occurring. Which of the following structures does streptomycin most likely directly bind to?
　　Nucleus
　　Golgi Apparatus
　　Vacuole
　　Nucleolus
　　Ribosome
　　本题考察16S rRNA的位置，rRNA是ribosomal RNA因此位于Ribosome选E.
　　Which of the following proteins most likely contains a nuclear localization sequence?
　　A. Kinesin
　　B. Collagen
　　C. Ubiquitin ligase
　　D. Phosphofructokinase
　　E. Estrogen receptor
　　USABO生物竞赛
　　Estrogen作为female sex hormone 是一种hydrophobic的steroid hormone，会结合cell内部的receptor并形成hormone-receptor complex，进一步进入Nucleus去regulation gene expression。因此Estrogen receptor含有nuclear localization sequence 选E.
　　A gram stain is performed to determine whether a bacterial species is gram-positive or gram-negative. Which of the following steps is part of the procedure?
　　I. Staining with safranin
　　ll. Immunoprecipitation
　　III. Visualization with UV light
　　IV. Staining with crystal violet
　　A.I and IV only
　　B.ll and Ill only
　　C.ll and lV only
　　D.I, I1I, and lV only
　　E.I, II, I, IV only
　　USABO生物竞赛
　　Gram stain 是一种鉴别bacteria cell wall结构的染色法，过程需要用到Crystal violet和Safranin因此选A.
　　Jonah is a farmer-scientist who cultivates a plant that produces aggregate fruit and is known to follow the ABC hypothesis. He wants to produce various mutants of this plant in an attempt to increase fruit yield. Which of the following mutant plant forms would improve fruit yield the most?
　　A. Constitutive expression of a cytokinin-producing gene
　　B. Deletion of the B gene
　　C. Expression of genes that increase phloem plasmodesmata
　　D. Overexpression of the A gene
　　E. Overexpression of the C gene in areas where the B gene is expressed
　　USABO生物竞赛
　　本题考察花的ABC hypothesis，想要生成更多的fruit，需要在保留B gene的条件下overexpress C gene 故选E.
　　Three plants display different mutations related to the plant hormone ethylene:
　　- ein: ethylene-insensitive
　　- eto: ethylene overproducing
　　- ctr: constitutive triple response
　　Farmer John crosses these plants with each other and with WT plants in an attempt to produce short offspring. Which of the following crosses is least likely to produce short offspring, and should thus be avoided by Farmer John?
　　A. WT with ctr
　　B. WT with eto
　　C. ein with eto
　　D. ein with ctr
　　E. eto with ctr
　　USABO生物竞赛
　　根据植物Ethylene的triple response，ethylene越多植物越矮，题目要求选最高的，应是不响应ethylene的植株，ein，同时eto不能recover这种不响应，故选C.
　　A red blood cell traveling between which pair of locations (in the direction of first location to second location) would have the least distance to travel?
　　A.Left Atrium Cardiac Muscle to Left Atrium
　　B. Left Lung to Right Lung
　　C. Liver to Adrenal Gland
　　D. Small Intestine to Liver
　　E. Stomach to Spleen
　　USABO生物竞赛
　　Hepatic portal vein的存在使small intestine直接连接liver，因此选D.
　　Ruffles has a condition where he retains too much water, causing him to feel bloated. His doctor prescribes a diuretic with the unfortunate side effect of shuttling protons through the inner mitochondrial membrane, which significantly reduces the yield of cellular respiration. Which of the following portions of the kidney would be most affected by this?
　　A. Proximal Convoluted Tubule
　　B. Descending loop of Henle
　　C. Ascending loop of Henle
　　D. Distal Convoluted Tubule
　　E. Collecting Duct
　　USABO生物竞赛
　　Nephron中的distal tubule是进行一系列osmolality regulation的主要位置，因此发生最多的active transportation，因此受影响最大，本题选D.
　　Which of the following statements is true about CD8?
　　A. It's most commonly found as an intracellular glycoprotein
　　B. The D1 domain can bind to MHC ll from antigen-presenting cells
　　C. It's a marker of cytotoxic T cells
　　D. It's a highly polymorphic protein
　　E. CD8 markers are an effective screening tool for the diagnosis of Human immunodeficiency Virus
　　USABO生物竞赛
　　CD8 protein是Cytotoxic T cell的marker故选C.
　　Aphids, herbivores with a short generation time, have been observed to run on S. niknud sap as a new food source. S. niknudsap initially had a lower cost of acquisition but greater foraging time relative to T. do sap. Which of the following would best explain the given change in aphid herbivory patterns?
　　A. Imprinting
　　B. Optimal foraging model
　　C. Game theory
　　D. Spatial learning
　　E. Problem-solving
　　According to the optimal foraging model, natural selection should favor a foraging behavior that minimizes the costs of foraging and maximizes the benefits. 因此本题中Aphid的行为符合optimal foraging model故选B.
　　In a BLAST sequence similarity search on the NCBI website, which of the following proteins will likely have the highest sequence similarity to Porpoise cytochrome c?
　　A.Human cytochrome c
　　B. Manatee cytochrome c
　　C. Sheep cytochrome c
　　D. Zebra cytochrome c
　　E. Horse cytochrome c
　　USABO生物竞赛
　　本题考察Mammal diversity，对于mammal而言Porpoise和sheep同属于Cetartiodactyla因此cytochrome c的similarity应最高，故选C.

　　以上便是关于USABO竞赛真题的介绍了，作为一家拥有30年经验的留学机构，顶试留学不仅拥有丰富的名校资源，也拥有中英美专家团队，能因地制宜地制定个性化的留学方案，让学生们能顺利进入自己的梦中情校。如果您在筹备赴英留学的过程中遇到任何问题，都欢迎联系顶试留学。