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Extracting DNA Experiment.

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  • SL Core /
  • Molecular biology: Activities for Learning/
  • Extracting DNA Experiment.

Experiment to Extract DNA from Plant Cells

DNA (Deoxyribonucleic acid) is the genetic material of all organisms, DNA is universal. We find the same genes performing the same functions in all species living on Earth.

Since all living things contain DNA molecules we can safely extract it from a wide range of living things including; Peas, Strawberries, Yeast, Bananas and Onions and even Liver from the butchers.

Lesson Description

Guiding Questions

Do all living things contain the same type of DNA molecule?

Is the genetic code, ATCG, a universal code making the same proteins in all species?

Activity 1: Experiment to Extract DNA from Plant Cells

Carry out the experiment on the Students' Worksheet - Extracting DNA from Onions and Bananas. Does the data you collect support the hypothesis of the universality of DNA, at least in plant cells?

Activity 2 - IB Style Questions

Try these IB Style questions on DNA structure

Activity 3: Extension Questions

  1. Sodium chloride (NaCl) ionizes in solution, i.e., NaCl into Na+ and Cl-.
    How do you think the negatively charged phosphate groups of DNA will respond to the Na + and Cl- ions?
  2. If you had access to a high tech laboratory, what investigations could you do with the DNA that was extracted from the onion and banana?

Try  this   Build DNA online at the University of Utah

Teachers notes

This is a simple experiment in essence and the method give adds an IB twist by suggesting the hypothesis that DNA is universal, and suggesting that the experiment can provide evidence to support this hypothesis.

The worksheet includes questions which help students to practise writing answers like those in IB exams.

Answers to IB style questions on DNA structure

The experiment should take an hour in the laboratory, including the questions. There are many options for group working. Student could carry out both extraction ofr DNA from Banana and also from Onions, or groups could be allocated one type of plant cells and students could compare their results at the end.

Of course eny evidence from this experiment is likely to be rather inconclusive, there are so many possible variations in the look of the DNA which may be caused by impurities in the sample. At least the very fact of finding DNA in both samples will support the hypothesis.

Some other methods for extracting DNA can be found here: