DNA
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.
Zoom in on Your Genome
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.
Origami DNA
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.
Yummy Gummy DNA, another modelling activity can be found at http://stem.org.uk/rx6yx
Explaining Inheritance
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.
Create a DNA Fingerprint
This is a nice little simulation of a crime being solved using a DNA fingerprint. To run the simulation, press the View button on the web page.
It describes the original process of DNA fingerprinting, using gel electrophoresis and blotting. This process has now been superseded but this type of result is often the type shown in examination questions or on television programmes.
Students can try the simulation and then produce a flow chart to describe the process of DNA fingerprinting. Students can be challenged to explain:
• Why are restriction enzymes used?
• How does electrophoresis separate the fragments of DNA?
• Why are radio active DNA probes added?
• Why are DNA fingerprints unique to each individual?
The animation is from the USA and they use the term Jell-O to describe the agarose gel. Students may need to be told that this is just a term for jelly.
Commercially-available kits are available that will allow students to run DNA fingerprints (without the use of the radio active markers) in the school laboratory.
Forensic DNA profiles are currently produced by a process called SGM+. For a brief explanation of this process, see page 13 of the teachers notes or slide 4 onwards in the presentation found at: http://stem.org.uk/rx3jc
Protein synthesis animation
The process of producing a protein from a gene is complicated. This animation helps students to visualise the different stages. There are many animations available on the internet for this process but most are aimed at too high a level for 14-16 students. This one is pitched quite high but about right.
It is worthwhile going through the animation in stages and explaining each one. Students may need to be reminded that it is the sequence of bases on the DNA that hold the information to make the protein.
A useful analogy is one of the letters of the alphabet. In themselves, each letter does not hold any information. However, when joined into words and sentences, they can convey complex information. The four bases of DNA are sometimes called the genetic alphabet.
You, or your students, can produce a series of cards, each with one discreet processes involved in protein synthesis. After watching the animation, students can sequence the cards and produce a flow diagram of the process for their notes.
Use the topic to also reinforce and revise students’ knowledge of proteins as a long chain of amino acids joined end-to-end.
Ceri Evans' Masterclass: DNA
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.
