Genes and the Genetic Code

Discover how DNA contains the instructions for life.

  • Credit: Paul Wilkinson

Introduction

We have developed a series of clips to explore the Life Fantastic with your students. The pages are intended for use as a prompt to help you prepare when exploring these topics in lessons. Teachers have told us that the videos and questions best suit being used as a topic introduction.

On this page you will find an overview of the topic covered by the clips, a brief summary of each clip, related questions and how the topic links to the curriculum.  This is one of eight available resources on developmental biology. For more topics see the teaching resources list.

Overview

DNA is a code, an instruction manual for all life. But how does it influence what a cell becomes? The clips introduce the triplet code and how this relates to an amino acid sequence. 

Topics in the videos

  • Understand that DNA contains a code – the genetic code.
  • Understand that the genetic code is arranged in units of 3, which is used in the production of amino acids
  • Describe how the genetic code needs to be arranged in triplets to produce the correct number of amino acids
  • Understand that not all DNA codes for a gene, but that genes are discrete units of the DNA and are a sequence of nucleotide bases
  • Explain how genes are not expressed in every cell but in particular cells
  • See an example of genetic modification in a worm expressing GFP

The material in this resource is supported by video clips from the CHRISTMAS LECTURES 2013.

Curriculum links

This resource is suitable for Key Stages 3 and 4 and AS/A2 level. Full curriculum links are given at the bottom of the page.

Clip 1 - DNA - the code

The clip starts with the conundrum – how does the DNA code influence what a cell is to become? How do four DNA letters give rise to the 20 different amino acids we find in proteins? The answer lies in the degenerate triplet code. Alison Woollard decodes a DNA sequence into amino acids live in the theatre, showing how each group of three DNA letters, the codon, gives a single amino acid. Looking at the fully decoded sequence, we find a jumble of letters demarked by a number of points of punctuation. This jumble represents possible amino acids, but amongst this are two sentences representing two protein-coding genes.

Running Time: 3 min 37 secs

Summary questions

  • How many amino acids could you make if the DNA code consisted of just one base? What about a two base code? What about a three base code? (1 amino acid; 16 amino acids; 64 amino acids, 1:04)
  • What is a codon? (A group of three bases, 2:03)
  • What is a sequence or chain of amino acids called? (A protein, 2:48)

Background and discussion questions

  • What do you call a sequence of bases? (A gene)
  • What does a gene code for? (A protein)
  • What is the name of the intermediate molecule, made from the DNA before being translated into a protein? (RNA)

Clip 2 - Gene expression

With the help of an audience member Alison Woollard finds two sentences within the translated DNA sequence. Amongst the amino acids are ‘MAKEALIVERCELL’ and ‘MAKEAHEARTCELL’. These sentences represent two different proteins that are encoded in the DNA. Alison explains that the proteins produced by these two genes could have different roles and cause the cells to do different things. But how do we get different cells if all our cells contain the same DNA? In the final part of the sequence, Alison explains that these genes are turned on and off in different cells and it is by this mechanism that even though every cell in our body contains the same genes, we can still have a great diversity of cells.

Running Time: 4 min 32 secs

Summary questions

  • Which are the proteins in the amino acid sequence? (MAKEALIVERCELL and MAKEAHEARTCELL, 0:55)
  • What regulates how the gene is turned on and off? (A switch, 3:18)

Background and discussion questions

  • Where are proteins made in the cell? (Cytoplasm)
  • What might the two proteins highlighted do? Where do you think you might find them?
  • Name some other proteins or enzymes and jobs they have in different cells.
  • Only two genes encoding proteins are found in the wordsearch. What is the common name for the rest of the DNA that doesn’t code for proteins? (‘Junk’ DNA)
  • What would happen to the cell if both genes were switched on? Would it develop properly?
  • How might the genetic switch be controlled inside the cell?

Clip 3 - Green Fluorescent Protein

Next in Where Do I Come From?, Alison introduces a widely used genetic engineering technique – the copying and pasting of the gene encoding green fluorescent protein (GFP) from one organism to another. In this example the GFP gene from jellyfish has been transferred into nematode worms. GFP fluoresces in the muscle cells of this worm because the GFP gene is being switched on when the muscle protein gene is also switched on.

Running Time: 3 min 20 secs

To extend this resource for A-level students, take a look at the Royal Institution’s series of videos on the human genome, Chromosome. Within this series are a number of videos looking at different genes. Of particular relevance to the discussion of gene function and gene expression are chromosome 13, which looks at two genes that are important in the control of cancer, and chromosome 16, which looks at the gene which is altered in people with ginger hair.

Curriculum links

KS3

Conforming to ‘Genetics and Evolution: Inheritance, chromosomes, DNA and genes’, this resource expands on knowledge of genes and introduces the triplet code of DNA.

KS4

The resource explains the genetic code found in the DNA and introduces the idea of a sequence of bases corresponding to a sequence of amino acids in a protein and corresponds to the requirements in:

  • AQA GCSE Biology 4401/Additional Science 4408 Unit 2: Biology 2 B2.7.2 ‘Genetic variation’;
  • Edexcel GCSE Biology 2BI01/Additional Science 2SA01 Unit B2 Topic 1 ‘The building blocks of cells’ 1.22 and 23;
  • OCR GCSE Biology A J243/Additional Science A J242 Unit A162 Module B5 ‘How do genes control growth and development within the cell?’ B5.3.

The clips go beyond the specification requirements by discussing the triplet code, though they introduce the concept with a simple exploration of how DNA codes for the correct amount of amino acids and how a group of amino acids can make different proteins.

AS/A2

The clips provide a platform for the discussion of the genetic code. They describe the triplet code found in DNA and how this results in a corresponding amino acid sequence. They also illustrate how gene expression needs to be controlled in order to express the correct gene in the correct location and give an example of where this is taken advantage of in a gene cloning technique with green fluorescent protein. This conforms to:

  • AQA GCE Biology AS 1411 Unit 2 BIOL2 ‘The variety of living organisms’ section 3.2.2, Unit 5 BIOL5 ‘Control in cells and in organisms’ sections 3.5.6, 3.5.7 and 3.5.8;
  • OCR GCE Biology AS Unit F212 Module 1 ‘Biological molecules’ 2.1.2 and Unit F215 Module 1 ‘Cellular Control and Variation’ 5.1.1. 

Related content

Use these resources on TED-Ed

TED-Ed: DNA - the code

TED-Ed: Gene expression

Watch the full lectures

View the full CHRISTMAS LECTURES, Life Fantastic, along with behind the scenes footage, and related content, at the Ri Channel (www.richannel.org).