Genome and Gene expression
Students find the topics of genome and gene expression difficult. Through exposure in the media and popular science, students are often aware of a range of terms such as: DNA, chromosome, genes, genetic engineering etc and they know that genes are used to carry information.
However, this over exposure can lead to misinformation and misconceptions with students understanding; they struggle to appreciate the relative size of DNA, the nucleus and the whole cell, as media images often appear to show DNA and genes as something which appears visible. Using animations and images can help to put the structure of DNA into context and appreciate the scale of DNA molecule and chromosomes.
The level of detail that is required in the study of DNA is also not always understood by students, students must be able to describe DNA as a polymer made from four different nucleotides, and they must know that each nucleotide consists of a common sugar and phosphate group with one of four different bases attached to it. Students must also be able to give a simple description of protein synthesis, which includes explaining how DNA structure affects the proteins made in protein synthesis. This requires some time to deliver and careful planning is required to ensure that this content is covered effectively
Links and Resources
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.
In this video produced by Nowgen there are two practical activities demonstrated: making mucus and extracting DNA, it is the second one which is relevant for this topic.
In this practical activity the method for extracting DNA is relatively simple using mouthwash containing cheek cells. Along with the video, which is useful for both teachers and students there is an accompanying instruction sheet.
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
This Catalyst article is all about chromosomes: in particular, the article looks at genes and explains how the chromosomes and genes a human inherits from their parents can cause problems such as sickle-cell anaemia, cystic fibrosis and Huntington's disease.
The article provides a good reminder of the process of cell division and has some useful illustrations.
The level of detail about the coded instructions in DNA is described clearly and the context of mistakes in this coding sequence leading to possible diseases and conditions will help students to understand the importance of the process.
The article could be used as a focus for a small group activity, with students challenged to represent the process of protein synthesis in a flow diagram, or series of steps, or they could be asked to produce a glossary of all the important terms used in the article.
There are many ways to make effective use of Catalyst articles such as this. A booklet has been produced which provides ideas on how Catalyst articles can be used with students and includes six exemplar activities. This booklet can be accessed at: https://www.stem.org.uk/elibrary/resource/27308>
This animation from ABPI has some very useful animations within it.
Pages 1 and 2 are most relevant to this topic area, although all 8 pages link together a number of GCSE Biology topics.
Pages 1 and 2 would work well as an independent study activity either for individual students or in pairs.
On page 2 the animation that shows the cell all the way through to DNA helix will support students understanding of relative scale of the DNA molecule.
Students will enjoy changing the baby’s eye colour.
The protein synthesis animation is simple but effective.
There are then 9 questions, with multiple choice answers that will auto mark, so students can revisit any questions they answer incorrectly
This is a simple activity, designed for Key stage 3, to introduce genetic conditions and how gene therapy is being developed to try to treat them.
Students undertake a simple modelling activity to investigate chromosomes in a nucleus, representing this using string or wool and moving about the classroom.
There are then some questions to answer on a provided worksheet.
This resource, from Genetic disorders UK, links with the topic of inheritance and is part of a collection of materials about a boy who has a rare genetic condition.
This activity is useful as a recap on Key stage 3 knowledge and as a starter for further work on this topic.
This animation describes how DNA is tightly packed in the nucleus of every cell.
Whilst the level of detail within the animation is at times above the required level of GCSE, it is still a worthwhile animation to show as it reinforces the idea of scale with the magnification at each stage clearly shown.
Within this resource is a practical activity for extracting DNA from strawberries. It is possible to use a range of other materials: kiwi fruit, onion or liver. Students could investigate the best source to use.
If using strawberries these should not be ground up too much, grinding generates heat and this can damage the 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 300C
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 is a resource for teachers.
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.
Watching the video will provide teachers with some concrete and accessible ways to teach the topic of DNA.
This resource from the Sanger Institute, is a craft based activity most suitable for classroom use or science festivals where students make a DNA sequence bracelet that carries part of the code of an organism such as a human, trout, chimpanzee or butterfly.
The activity reinforces the principle of complementary base pairs as they are given one strand of the sequence and they have to match up the other strand correctly.
This resource produced by the Wellcome Trust Sanger Institute, requires students make their own edible DNA double helix model out of Jelly Babies and cocktail sticks.
Through this activity students are learning about the basics of DNA structure and complementary base pairs.