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Biology Summer School 2013 Use of UV-sensitive yeasts at Higher and Advanced Higher Kath Crawford, Lorraine Bruce. Aims. Explore the use of UV-sensitive yeasts to support learning and teaching of Biology and Human Biology at Higher Level. Unit: Metabolism and Survival
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Biology Summer School 2013 Use of UV-sensitive yeasts at Higher and Advanced Higher Kath Crawford, Lorraine Bruce
Aims • Explore the use of UV-sensitive yeasts to support learning and teaching of Biology and Human Biology at Higher Level
Unit: Metabolism and Survival 3. Metabolism in microorganisms (b) Genetic control of metabolism (i) Wild strains of microorganisms can be improved by mutagenesis, selective breeding and culture or recombinant DNA
Unit: Human Cells 2. Structure and function of DNA (c) Genes and proteins in health and disease (ii) Mutations result in no protein or a faulty protein being expressed
Unit: Investigative Biology • Scientific principles and process • Experimentation • Critical evaluation of biological research
Ultraviolet (UV) light • < 400 nm • More energetic than visible light • Can disrupt chemical bonds • Causes increased mutation rate in DNA
Wild-type yeasts (and other eukaryotic cells) • DNA routinely damaged from exposure to UV radiation in atmosphere • Protection mechanisms • enzymes repair DNA damaged by UV radiation • sometimes fail, mutations occur • Repeated exposure to UV light increases rate of damage and chance of mutations
UV sensitive yeasts • Mutations in genes necessary for DNA repair • Deficient in DNA repair mechanisms • More sensitive than wild-type cells to sunlight
The activities • Expose UV-sensitive yeasts to sunlight or UV radiation for varying lengths of time (demonstration only), compare with wild-type • Carry out a simple investigation to test whether sunscreens offer protection to the damaging effects of UV irradiation
Results – Yeast survival vs. time ‘sunbathing’ 10 min 20 min 0 min 40 min 30 min
Using aseptic technique, pick off a small, isolated colony from the master plate of • UV-sensitive Saccharomyces cerevisiae and add to 10 cm3 sterile Ringer’s solution. Mix well. • Using aseptic technique, carry out a x10 serial dilution to achieve a final dilution of 10-3
Aseptically, pipette 100 µl 10-3 dilution onto each of 5 labelled YGA plates • Use sterile loop to spread evenly across plate, Sellotape closed Aluminium foil No cover E45 Factor 6 Factor 30 • Irradiate with UV for 1 hour (sunlight or UV lamp) • Incubate 30°C for 48 hours
Effect of different strengths of sunscreen on UV irradiation of UV-sensitive yeast No irradiation SPF O SPF 6 SPF 15 SPF 25
Use of yeast as a model organism • Implication of exposure to UV irradiation as a cause of skin cancer From melanocyte to melanoma
http://www.cancerresearchuk.org/cancer-info/cancerstats/incidence/commoncancers/#Twentyhttp://www.cancerresearchuk.org/cancer-info/cancerstats/incidence/commoncancers/#Twenty
Malignant melanoma is the fastest increasing cancer in males and the second fastest increasing cancer in females • Some of the increase may be due to increased surveillance and early detection as well as improved diagnosis • most is considered to be real and linked to changes in recreational or holiday exposure to UV rays (including sunlight and sunbeds)
http://www.metoffice.gov.uk/public/weather/forecast/#?tab=map&fcTime=1371427200&map=MaxUVIndex&zoom=5&lon=-4.00&lat=54.63http://www.metoffice.gov.uk/public/weather/forecast/#?tab=map&fcTime=1371427200&map=MaxUVIndex&zoom=5&lon=-4.00&lat=54.63
http://www.isdscotland.org/Health-Topics/Cancer/Publications/2012-10-30/Cancer_in_Scotland_summary_m.pdfhttp://www.isdscotland.org/Health-Topics/Cancer/Publications/2012-10-30/Cancer_in_Scotland_summary_m.pdf
Health Warning Sunbed use may damage your skin and will increase your risk of skin cancer!
What would we want the students to learn? • Knowledge and understanding • UV-irradiation causes mutations in DNA • Improvement to wild-type • Changes in protein expression • Yeast as a model organism • Relevance to understanding of skin cancer • Techniques • Serial dilution • Microbiology
Skills of scientific experimentation, investigation and enquiry • Planning and designing • Experimental design to ensure validity of procedures • Evaluating experimental procedures • Identify and comment on validity of experimental designs • Drawing conclusions • Draw conclusions on the relationships between the dependent and independent variables
Kath.Crawford@sserc.org.uk Lorraine.Bruce@sserc.org.uk