Students often find the topic of DNA quite a tricky one. Through exposure in the media and popular science, students are aware of the molecule and know that genes are used to carry information. However, a great deal more detail is required by the specifications and there is always the risk that students have deep-held misconceptions. For example, in the relative scale of the molecule, nucleus and whole cell.
In this list, several of the resources look to assist students in gaining an in-depth understanding of the structure of the DNA molecule. Using models and animations help to provide a range of ways in which students can tackle this abstract concept.
Finally, an animation that shows how DNA is used to drive protein synthesis is included. This is a very tricky process and time should be set aside to make sure that it is understood.
Whilst this list provides a source of information and ideas for experimental work, it is important to note that recommendations can date very quickly. Do NOT follow suggestions which conflict with current advice from CLEAPSS, SSERC or recent safety guides. eLibrary users are responsible for ensuring that any activity, including practical work, which they carry out is consistent with current regulations related to Health and Safety and that they carry an appropriate risk assessment. Further information is provided in our Health and Safety guidance.
Links and Resources
This animation can be downloaded and used on stand-alone computers.
The structure of DNA is quite difficult to put into context. Anything in biology at this scale is quite an abstract idea.
This animation helps students to focus down from the scale of the whole organism, through cell structure, into the nucleus and via chromosomes to the structure of DNA.
Making the animation available on the school network allows students to revisit it whenever they need to remind themselves of the scale, location and structure of DNA.
Note the way that chromosomes are represented. This is as single chromosomes arranged as matching pairs. This is an excellent representation. A lot of pictures will show chromosomes in a classic ‘X’ shape. This representation is misleading. They are chromatids formed during mitosis. These are an original chromosome and its replicated copy joined at the centromere.
Activities that help students to understand the structure of DNA are very valuable. Making a model of DNA using a template can be a useful way of showing students how DNA forms the classic double helix form.
The activity includes templates and instructions.
Once students have made the model, they can be challenged to make a different representation using simple ‘raw materials’ such as thin card, sticky tape and lolly-ice sticks. This will help them to further explore their understanding of the molecule, as they will need to create a representation from scratch.
The activity can be completed by reminding students that Watson and Crick (Nobel prize winners) used models to discover the structure of DNA.
This article is from Catalyst, a magazine specifically written for 14-16 students. It describes the stages in discovering that DNA was the molecule responsible for passing on inherited information.
The article can be used as a focus for a small group activity (pairs or threes).
Challenge students to clearly show the sequence of events, and the build-up of evidence, that pointed to DNA being the molecule responsible for inheritance.
Listening to discussions provides an opportunity to assess understanding.
This activity shows how scientific discoveries build one on the next. It also allows students to practice skills in interpreting and presenting information.
Once groups have completed their initial discussion, they can then be mixed to allow students to compare each others’ interpretations. These second discussions can often allow students to tackle any misunderstanding.
Students can perform the practical activity, Extracting DNA from strawberries. This practical activity sees students isolating DNA from strawberries.
A range of materials can be used and classically the fruit of choice was kiwi fruit. Other sources can include onions or liver from the butchers.
Students could investigate the best source to use.
Whichever source is used, it is wirthwhile checking that students do not have any allergic or sensitivity reactions to the source. Some students can show an allergic response to Kiwi fruit.
The strawberries do not need to be ground up too much. Grinding generates heat and this can damage DNA. It will suffice to mush them up on a cutting board.
The protocol described suggests leaving the mixture stand for 10 minutes at room temperature. The process may be enhanced by incubating at a warmer temperature, for example 30oC.
As an extension, adding a protease (take care as they may be an irritant) can sometimes aid the extraction as they break down proteins in the nucleus. A comparison with and without protease could be a useful investigation.
Depending on the success of the extractions, thin wispy clumps of DNA can be seen in the ethanol. Stress to students that these are not individual strands of DNA. Do not reinforce any misconceptions on scale.
If sufficient DNA is produced, it may be scooped out using a blunt seeker or similar.
This video shows an active lesson about DNA. It looks at the base pairs in DNA and how the DNA sequence is translated into the amino acid sequence of a protein.
The lesson provides science teachers with some concrete and accessible ways to teach the topic of DNA.