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

这个实验使用强大的聚合酶链反应（PCR）的新技术来证明人类DNA的可变性质。尽管人与人之间的DNA相似多于不同，但我们基因组的某些区域表现出极大的多样性。这种可变序列被称为多态（意味着多种形式），并为亲子鉴定和DNA法医测试提供了基础。在大约90%的不编码蛋白质的基因组中发现了许多DNA多态性。这些多态性的一个特殊类别被称为Alu插入。Alu元素是短的DNA序列，已经扩增到大约50万个拷贝，分布在整个灵长类基因组中。这些Alu插入中的一些发生在过去的100万年里，并没有固定在人类基因组中。学生们使用简单的漱口程序（无血无创）获得自己的DNA样本。PCR用于在组织纤溶酶原激活基因的内含子上进行扩增，该内含子可能含有Alu插入。如果存在Alu序列，则产生400 bp的PCR产物，而当不存在Alu序列时，则产生100 bp的PCR产物。扩增后，学生样品被装入琼脂糖凝胶，电泳，染色，并拍照。每个学生都会在他们的凝胶通道中看到一到两条条带，表明它们是Alu插入的纯合子，没有插入的纯合子，还是插入的杂合子。

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.