What does DNA look like?

Saraswathi Jayanthi and Vinay Singh

All of us have heard about the DNA (Deoxyribonucleic acid), but how many of us have seen it? It may surprise you to know that you can actually see the DNA by a simple extraction process. This article is divided into three parts for easy adaptation into a lesson plan.

  • Quiz – warming up activity
  • Laboratory activity – DNA extraction
  • Questions and discussion

test As biology teachers we have seen students showing a lot of curiosity and enthusiasm to learn about the DNA – the wonder molecule. Students of middle school are familiar with terms such as prokaryotic cell, eukaryotic cell, nucleus, chromosome, nucleic acids, RNA, and DNA. Though students have an idea about these terms, sometimes they may not be clear as to what these terms actually mean. Before going into a discussion on the structure of the DNA and its role and significance, the teacher can have a small warm up activity like a quiz in class. Here are some questions you can ask your students.
1. What is the difference between a prokaryotic and a eukaryotic cell?
2. Give examples of prokaryotic and eukaryotic cells.
3. What is the key cell organelle in a eukaryotic cell?
4. What is present inside the nucleus?
5. What are nucleic acids?
6. Where do you find them?
7. What do you understand by the term genetic material?
8. What is the difference between DNA and RNA?
9. What is a chromosome?
10. What is a gene?

Guide your students in understanding the terms chromosome, DNA, and gene and sum up the topic as below.
In eukaryotes most of the DNA is held inside the nucleus, though some DNA is contained in the mitochondria and chloroplast. In prokaryotes, the DNA lies in the cytoplasm as a coiled circular molecule known as nucleoid. DNA is the genetic material in most organisms with the exception of a few viruses. It is a negatively charged molecule made up of nucleotides.

Now, as the students have a basic understanding of the DNA, you can have a hands-on activity which enables them to actually see the DNA. Here we present a simple method for the extraction/isolation of the DNA from two sources.

Extraction of DNA from eukaryotic cells – banana
Materials required

  • Fresh banana
  • Knife
  • Mortar with pestle
  • Extraction solution/buffer
  • 500 ml beaker
  • Funnel
  • Cheese cloth (cut to fit over a small beaker)
  • Test tubes
  • Hot water bath set at a constant 60°C or a beaker of water set at 60°C using a thermometer
  • Ice water bath (a beaker containing crushed ice)
  • Measuring cylinder
  • Dropper
  • Alcohol
  • *Centrifuge (optional)
  • Distilled water

Dr. Saraswathi Jayanthi is a biology teacher and ICSE & ISC Coordinator at Sreenidhi International School, Hyderabad. She can be reached at saraswathij@sis.edu.in.

Mr. Vinay Singh is a biology teacher at Sreenidhi International School, Hyderabad. He can be reached at vinays@ sis.edu.in.

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