Extracting DNA
DNA is the most important component of chromosomes and is wound up very tightly within the nucleus of the cells of all living things. Every organism has a unique number of chromosomes.
DNA in an organism. It’s a blueprint for all of the instructions of how that cell is going to behave and how it’s going to be replicated.
All human cells, with the exception of red blood cells, contain 46 chromosomes. If all the DNA contained in the chromosomes of one human cell was unwound and the pieces were stretched out in a line end to end, it would be almost 2 metres long. There are approximately 100 trillion cells in the human body, so our bodies contain more than a billion kilometres of DNA!
The long stringy nature of DNA is hard to conceptualise. By extracting it, the concept can become easier to understand. Extracting DNA from cells is a common technique used by scientists studying genes and other fields such as microbiology.
In this activity, students will extract the DNA from a tomato.
Double helix DNA
A diagram showing the double helix structure of DNA.
DNA helix by MesserWoland, CC BY 2.5.
By the end of this activity, students should be able to:
extract and observe DNA from a tomato
explain that DNA is common to all plants and animals
explain that DNA holds genetic information for plants and animals.
Download the Word file (see link below).
Related content
Other articles that provide interesting and useful reading to support students building their understandings of the concepts related to DNA include: DNA, chromosomes and gene expression, DNA and biotechnology and Biology idea 5: Organisation.
Activity ideas
Activities that may be useful to do before doing this activity are: Introduction to cells and Inside a cell with the related activity DNA detective.
Useful links
The method described in this activity is based on a method by Petra Frey.
Another method of DNA extraction from Learn.Genetics is described here.
