UPD8

Getting Tanned

Learning objectives

Pupils will improve their enquiry skills in selecting a suitable question to be investigated, and deciding the extent and range of data to be collected. They will reinforce their work on cells, by finding out which cells are responsible for making melanin in tanned skin; they will learn how different tanning methods work, including the synthetic hormone being tested by Australian scientists, and discuss the pros and cons of each method.

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Curriculum link

9a Inheritance and selection
• identify some characteristics that are influenced by environmental factors
• identify environmental factors that influence characteristics of an individual
9M Investigating scientific questions
• know how to identify ideas that can be investigated.
• consider sample size and possible effect of other factors in evaluating the limitations of the evidence.

Running the activity

Page 1 introduces the topic and page 2 sets the first task. Students have to answer questions about getting a tan, for an advice page in a teen magazine. Individuals or small groups will need copies of page 3. This shows how each tanning method works and outlines each techniques advantages and disadvantages. If time is short, each group could answer a different 'letter', and the results could be pooled in a plenary session at the end. Page 4 sets a second task. Students are prompted to discuss what else they'd like to know about one of the tanning methods, turn it into a scientific question that could be investigated, and decide what data needs collecting.

Background Notes

Students may be interested to know that melanotan cannot be taken as a pill because it is a hormone-like protein and would be digested before entering the blood. During initial testing, melanotan was injected directly into the blood. But 1/6 participants dropped out due to side effects like nausea and vomiting. Sprays and implants are being trialled on 1000 participants. These release the drug into the bloodstream much more slowly, so they should reduce the side-effects. It will be at least 18 months before regulators give the final OK for the product to be marketable. Then tanning salons watch out!

New skin cells are made at the bottom of the epidermis and pushed upwards. Melanocytes release vesicles of melanin which are taken up by new skin cells. There is more than one form of melanin and the way it is packaged and stored in cells affects the exact colour produced, which is largely controlled by the genes. UV damage to skin cell nuclei releases signal molecules which stimulate increased melanin production. When rising skin cells get too far away from blood vessels they die, and are sloughed off the surface. Freckles occur where the melanocytes in small areas of skin produce bigger packages of melanin. Moles are the result of melanocytes clustering together in one spot, instead of being spread evenly though the skin. UV damage increases the risk of skin cancer. Cancer in ordinary skin cells is usually curable. Cancer in melanocytes is more likely to be deadly.

Students will be aware of what Michael Jackson has done to his skin. Some skin lightening treatments inhibit one of the enzymes involved in melanin synthesis. Two very rare, genetic diseases affect the skin's pigmentation. People with xeroderma pigmentosum are unable to repair UV damaged DNA and those with phenylketonuria cannot make enough of the amino acid tyrosine, which is needed for melanin production.

Web links

News links

Guardian

A report on the Australian company developing Melanotan.

New Scientist

Plenty details with a skin diagram, and discussion of the various methods of tanning.

Howstuffworks

Everything you could want to know about tanning explained in bite-sized chunks.

Epitan

Links to videos and an animation showing how melanotan works.

BBC

The science of tanning explained with the aid of an animation, and links to quizzes and a timeline showing how sunbathing came into fashion.

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