DNA and protein synthesis
In this topic at A level, students need to understand the structure, role and function of DNA and RNA. They must appreciate how the sequence of bases in the DNA molecule determines the structure of proteins, including enzymes. A common misconception seen in this topic is confusion between DNA and proteins. Students need to understand that DNA is a sequence of bases, whilst proteins are a sequence of amino acids. Spelling is another difficult area in this topic as there is a big difference between Thymine, in a DNA base, and Thiamine the vitamin.
The processes of transcription and translation continue to be areas which cause problems in final assessment. It is highly likely that an exam paper will contain a question on protein synthesis. Students need to be prepared to describe a specific part of the process or write a long answer question on the whole process.
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Links and Resources
This is actually three resources in one. It provides some really useful, easy to use material for A level biology.
The resource is made up of three separate animations: Zoom in on your genome, DNA sequencing and DNA to protein. Different specifications and schemes of work will determine in which order to use these animations most effectively.
Using Zoom in on your genome first would provide a good level of detail on the arrangement of chromosomes, the nature of the double helix and base-pair structure. Following this with DNA sequencing would allow students to develop an understanding of three different methods of sequencing DNA. The final animation (possibly Year 13) would be DNA to protein which provides detail on the process of transcription.
Each animation works as a stand-alone resource, for whole class delivery of new material or revision material. Students could also work through the animations individually. It is possible to use the animations at a set pace or move through each section separately.
This article is from the Catalyst magazine and although originally written for 14-16 students the information provided could easily be used with A level students.
Small groups or pairs of students could be given the article to review. The task they have is to convert this text into an alternative format which clearly shows the sequence of events, and the build up that pointed to DNA being the molecule responsible for inheritance.
Students can chose the format in which they present the information - this could be a poster, a leaflet, a PowerPoint presentation, a podcast or any alternative form of interpretation.
Once students have completed their interpretation in their chosen format, pairs could be mixed up to allow students to compare each other's interpretation and discuss.
17 videos, animations and images showing the chemical structure of DNA, base pairs, hydrogen bonding, centromeres, telomeres, the double helix, DNA strands, coding sequences, chromosomes, Chargaff’s ratio and DNA packaging with histones.
This resource contains information, activities and practical investigations, which could all be useful for A level Biologists.
The teacher’s notes have some useful summaries whicht could be photocopied for students to use as revision notes. Students could be encouraged to highlight/annotate and amend these notes using their own class notes/specification and answers to exam questions.
The two practical activities are short; both focus on the extraction of DNA either from epithelial cells or from plant cells. Some schools do not allow human biological samples to be used, so the plant cell practical is an alternative procedure. There are a number of questions that could be asked of students to complement these practicals and therefore make them more relevant to A level.
This is another Catalyst article on how the structure of DNA was confirmed. It is a much shorter article than Explaining Inheritance also included in this list.
It may be appropriate to give some pairs of students this article to review and summarise, whilst other pairs tackle the more challenging Explaining Inheritance article.
This is a set of films, animations and images which show DNA replication
This is a concise two page resource, which provides A level standard information on protein synthesis followed by nine questions for students to answer. There are teachers notes provided within the resource which give the answers to the questions.
There are a number of ways that these questions could be used: they could simply be used as questions to be completed individually either in class or for independent learning, students could answer the questions and peer assess the answers, the activity could be a timed activity where different pairs answer different questions and then these are moved round the class for the next pair to mark and add additional information.
This resource was originally intended for use with AQA specifications (pre Sept 2015), but are applicable to any Awarding Organisation.
This is quite a detailed resource package, which could be used across a number of lessons, although it would also be possible to just use the resources provided for shorter activities.
Essentially the activity requires students to determine the amino acids generated by particular code sequences, and then knowing the amino acids deduce which protein would be produced.
A range of resources are provided to allow students to complete this activity including a Codon wheel, worksheets and presentation.
Understanding the structure of DNA is a concept that many students, including those at A level, struggle with. This then impedes further understanding of protein synthesis and gene technologies.
Modelling activities are a useful activity for many students to fully comprehend the structure or DNA. In this activity students make a model of DNA using a template, the template and instructions are included in this activity.
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.
There are also other modelling activities, such as Yummy Gummy, but this maybe at a too low a standard for A level. Although as an end of lesson activity it still has some worth, if students have not previously completed it at KS4.
This animation illustrates how mistakes made during DNA replication are repaired.
During DNA replication mistakes can occur as DNA polymerase copies the two strands. The wrong nucleotide can be incorporated into one of the strands causing a mismatch. Normally there should be an "A" opposite a "T" and "G" opposite a "C". If a "G" is mistakenly paired with a "T", this is a potential mutation.