A Novel Mechanism for Introducing Human Genome Research in Freshman Biology Classes

这个实验使用聚合酶链式反应（PCR）这一强大的新技术来证明人类DNA的可变性。 虽然一个人与另一个人的DNA相似性大于差异性，但我们基因组的某些区域表现出很大的多样性。 这种可变序列被称为多态性（意味着许多形式），并为DNA的亲子鉴定和法医学测试提供基础。 许多DNA多态性存在于估计90%的不编码蛋白质的基因组中。 这些多态性的一个特殊类别被称为Alu插入。 Alu元件是已经扩增到约500，00个拷贝的短DNA序列，分布在整个灵长类基因组中。 其中一些Alu插入发生在过去的一百万年内，并没有固定在人类基因组中。 学生使用简单的漱口程序（无血和非侵入性）获得自己的DNA样本。 PCR用于扩增可能含有Alu插入的组织纤溶酶原激活物基因的内含子。 如果存在Alu序列，则将产生400-bp的PCR产物，而当不存在Alu序列时产生100-bp的产物。 扩增后，将学生样本加载到琼脂糖凝胶中，进行荧光染色，染色并拍照。 每个学生将在他们的凝胶泳道中看到一个或两个条带，表明他们是否是纯合的Alu插入，纯合的插入，或杂合的插入。

This experiment uses the powerful new technique of polymerase chain reaction (PCR) to demonstrate the variable nature of human DNA. Although the DNA from one person to another is more alike than different, certain areas of our genome exhibit a great deal of diversity. Such variable sequences are termed polymorphic (meaning many forms) and provide the basis for paternity and forensic testing of DNA. Many DNA polymorhisms are found within the estimated 90% of the genome that does not code for protein. A special class of these polymorphisms is called an Alu insertion. Alu elements are short DNA sequences that have amplified to about 500,00 copies, distributed throughout primate genomes. A few of these Alu insertions have occurred within the last million years and are not fixed in the human genome. Students obtain samples of their own DNA using a simple mouthwash procedure (bloodless and noninvasive). PCR is used to amplify across an intron of the tissue plasminogen activator gene that may contain an Alu insertion. If the Alu sequence is present, then a 400-bp PCR product will result, while a 100-bp product is produced when the Alu sequence is absent. Following amplification, student samples are loaded into an agarose gel, electrophoresed, stained, and photographed. Each student will see one or two bands in their gel lane, indicating whether they are homozygous for the Alu insertion, homozygous for the absence of the insertion, or heterozygous for the insertion.