DNA (short for deoxyribonucleic acid): The material from which genes are made.
Trait: An inheritable characteristic of a living thing (say, eye colour in people).
Phenotype: The observable characteristic of a given trait (say, blue eyes, brown eyes).
Genotype: The genetic make-up of an individual for a given characteristic.
Gene: A gene is a length of DNA that codes for a specific protein, and proteins make bodies. Tongue rolling is an example of a trait that is linked to a single gene.
Procedure Students examine themselves and each other and note the following traits.
Male or female.
Earlobes free or fixed. (Free earlobes have a gap between the inner edge of the earlobe and the side of the head.)
Able to roll tongue or not able to roll tongue.
Hitchhiker’s thumb or non-hitchhiker’s thumb. (A hitchhiker’s thumb can bend backwards.)
Hair – however fine – between the joints of the fingers.
Normal sight or red-green colour blind. (See Materials below.)
Able to smell freesias, or not able to smell freesias.
Able to taste PTC (phenylthiocarbamide) or not able to taste PTC. (See Materials below.)
They enter their results into the Excel spreadsheet (see MillionSpreadsheet.xls). This tells them how many people like them there are in a given population (usually the population of the home town or city).
The spreadsheet also calculates how ‘special’ they are: for example, ‘People like you are found 1 in every 142’.
The Million Spreadsheet can be modified to work with different towns or cities. Simply highlight the cells D10 and D22 and, in the top formula line, change the number in the formula fx = 280000 / E9 -1 to match the population of your town or city. So, for example, if you live in a city with 100,000 inhabitants, the formula would be:
fx = 100000 / E9 -1
This information is written on a label that shows ‘how special they are’ (see MillionLabels.doc).
Again, these labels can be modified to fit your particular population.
Red-green colour blindness can be detected using the Ishihara Test (see Figure 1 overleaf). See http://www.kcl.ac.uk/teares/gktvc/vc/lt/colourblindness/plate1.htm for more examples of tests for red-green colour blindness.
Phenylthiocarbamide (PTC), also known as phenylthiourea, can be obtained in the form of PTC taste papers over the Internet from a number of suppliers. Search for ‘PTC taste papers’. It might be an idea to have something to take the taste away – say, sweets or mints. Some people find PTC extremely bitter.
We find that the ‘smelliest’ freesias are cream doubles.