A Question of Taste

A Question of Taste  Post 16  

Duration: 5-5.5 hours 

Over 2500 students each year take part in this popular, lab-based PCR workshop. An unusual human trait is explored through DNA extraction, PCR and gel electrophoresis enabling students to determine their own genotype in relation to tasting the bitter chemical PTC. The possible evolutionary significance of this characteristic is discussed, along with the broader social, medical and ethical implications of gene technology.

Key Words:

PCR. DNA. Genetics. Gene. Allele. Gel electrophoresis. Enzymes. Variation. Evolution. Ethics.

Learning objectives:

Gain direct experience of the techniques involved in using producing a genetic fingerprint of a sample of their own DNA, including using micropipetting, DNA extraction, gel electrophoresis, and PCR

Be able to define DNA as a long, thin molecule, composed of nucleotides, with a double helical structure 

Recognise that the base order of some of DNA acts as a protein code and that there is genetic variation between individuals 

Gain an understanding that DNA can be extracted and then manipulated and copied

Understand that PCR is a technique that enables us to select specific sections of DNA and copy them billions of times

Understand that gel electrophoresis is a way of analysing PCR results

Explore the ethical and moral issues raised by various applications of gene technology 

Analyse results to compare genotype and phenotype

Recognise how studying human DNA can help us understand the evolution of our own and other species

Relate their results to contemporary research on the evolution of bitter taste detection in humans and chimps

Appreciation the importance of accuracy and minimising contamination in the laboratory, particularly when working with DNA

Content: Example Timetable

10:00 - Arrival and welcome

10:15 - Introduction to protocol, DNA overview 

10:45 - Students cheek cell swab & micropipette practise

11.30 - Extracting DNA and PCR preparation 

12:00 - Lunch break and time to explore We The Curious

13.15 - Set up restriction enzyme digest 

14.00 - Restriction enzyme activity

14.30 - Gel loading 

14.45 - Genetic testing ethics and debate session 

15.00 - View results and summary 

15:15 - Departure or more free time to explore We The Curious

Curriculum Links:

OCR (Spec A): Development of practical skills in Biology, Cell structure, Nucleotides and nucleic acids, Genetics and evolution, the principles of the polymerase chain reaction and its application in DNA analysis, the principles and uses of electrophoresis for separating nucleic acid fragments

OCR (Spec B): Development of practical skills in biology, Nucleic acids, the principles and uses of the Polymerase Chain Reaction, the principles and uses of agarose gel electrophoresis, the nature and use of SNPs (single nucleotide polymorphisms) in human genome studies

AQA: Structure of DNA, Cell structure, DNA, genes and chromosomes, genetic diversity and adaptation, inheritance, using restriction enzymes to cut a fragment containing the desired gene from DNA, the principles of the polymerase chain reaction as an in vitro method to amplify DNA fragments, genetic fingerprinting

Edexcel (Spec B): Using gene sequencing, understand how PCR can be used to amplify DNA samples, and how these samples can be used to predict the amino acid sequence of proteins and possible links to genetically determined conditions, using gene sequencing and in forensic science, to identify criminals and to test paternity, using DNA profiling

WJEC: Working scientifically, nucleic acids and their functions, alleles as different forms of the same gene. Application of reproduction and genetics: gene technology and its applications; the sequencing of genomes, the use of PCR and recombinant DNA technology. The ethical implications of these technologies

Potential Hazards:

Students will work in a lab environment with TAE buffer and gel electrophoresis tanks.