2013 Volume 53 Issue 4 Pages 168-175
In the Science part of the new Course of Study at the lower secondary school published in 2008, the unit of "Regularity of inheritance and genes" is included again. In some textbooks of science newly published, "Extraction of DNA" is proposed as a practical work for students by the simplified method using saline solution and liquid dishwashing detergent. In this study, in order to revise and develop the simplified method and plant materials using in the practical work on DNA extraction at lower secondary schools, we tried DNA extraction by the simplified method from banana, strawberry, onion and broccoli as plant materials. We also examined the UV absorption spectrum of the extracted and precipitated substance as a cloudy mass from these plants, comparing it to the fibrous substance extracted by a commercially available DNA extraction kit. As a result of study, we here propose a revised method for DNA extraction using a mixture of 4% NaCl solution and 5% SDS solution (24:1) as an extraction solution and broccoli as a plant source, and the diphenylamine-colorimetric method for the detect of extracted DNA. Furthermore, based on trial lessons at the University attached lower secondary school, we suggest that the following descriptions rather than the detailed structure of DNA should be added to the textbook of lower secondary school; 1) DNA molecule is very small, so usually we cannot see it by our naked eye and 2) In the eukaryotic cells, DNA is present in the nucleus and forms some parts of the chromosomes when cell is dividing.
