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  • 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.

    Dr Adele Williamson

    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.

    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

    Activities that may be useful to do before doing this activity are Introduction to cells and Inside a cell and the related activity DNA detective.

    Other articles that provide interesting and useful reading to support students building their understandings of the concepts related to DNA include DNA and biotechnology and Biology idea 5: Organisation.

    Useful link

    The method described in this activity is based on a method by Petra Frey. Another method of DNA extraction is described here.

      Published 12 November 2010, Updated 5 February 2022 Referencing Hub articles
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