A Close-Up Look at PCR

The Polymerase Chain Reaction (PCR) is a fundamental laboratory technique that allows for the amplification of many copies of a desired DNA target sequence. Despite its prevalence, undergraduate students often have poor comprehension about the underlying molecular mechanisms of PCR and the components necessary to carry out the reaction. We designed an interactive modeling activity to help students visualize the underlying molecular processes of denaturation, annealing, and extension, and to see how PCR parallels in vivo DNA replication. During the activity, students mimic denaturation, annealing, and extension by synthesizing DNA strands from individual nucleotides and primers in the 5' to 3' direction. Because they carry out three cycles, students construct and observe the intermediate products that lead to the exponential amplification of the target sequence. Instructors can easily assemble kits from relatively inexpensive foam nucleotide pieces, and the models can be reused indefinitely. Field testing with first and second year undergraduates suggested that students productively interacted with the models to improve their understanding of PCR.

聚合酶链式反应（Polymerase Chain Reaction，PCR）是一项基础的实验室技术，它能够实现对特定DNA靶序列的扩增。尽管PCR技术广泛使用，但本科学生在理解PCR的潜在分子机制以及执行反应所需成分方面往往存在理解不足。我们设计了一项交互式建模活动，旨在帮助学生可视化变性、退火和延伸等潜在的分子过程，并了解PCR与体内DNA复制的平行关系。在活动中，学生通过从单个核苷酸和引物中合成DNA链，按照5'至3'的方向模拟变性、退火和延伸过程。由于他们执行了三个循环，学生能够构建并观察导致目标序列指数级扩增的中间产物。教师可以轻松地从相对低廉的海绵核苷酸零件中组装成套件，且这些模型可以无限次重复使用。对一、二年级本科生的实地测试表明，学生通过积极与模型互动，有效地提高了对PCR技术的理解。