Hairy Hands - genetics of mid-digital hair
Students imagine they are the 'agony aunt' in a teenage magazine. A young person has written to the magazine with a worry about hair on their hands. Find out all the genetics about hair on the fingers so that you can explain why some people have hairy fingers. Keep notes using the worksheets on this page. Use this information to write a reply to reassure 'Hairy Hands Help' on your magazine page.
Lesson Description
Guiding Questions
Is mid-digital hair simple genetics, caused by one gene with two alleles?
Could the genetics be more complicated, sex-linked or caused by multiple alleles?
Is there anything 'Hair Hands' can do? Read the letter below sent in by a teenage reader
Hairy Situation: Teen Magazine Letter to the Problem Page
Hairy Situation: Teen Magazine Reply to the Hairy Hands
Activity 1- Experiments to test theories about genetic inheritance
ToK Point
Biologists since Gregor Mendel use experiments to confirm theoretical ideas about inheritance of genes. Sometimes the first ideas are do not explain the whole story. The example of mid-digital hair is a great example of how a hypothesis has been disproved in experiments and gradually improved through time.sources
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Use the interactive applet Gamete Maker to create human gametes for the worksheet 'experiment.'
The allele for mid-digital hair is shown next to the chromosome inside each gamete.
H is dominant allele for Hair, h is the recessive allele for no-hair
Activity 2 - A second set of Experiments doesn't support the hypothesis
Answer the questions on the Human genetics 2 - new evidence casts doubt worksheet (click the eye icon to display the worksheet)
The Gamete Maker for sex-linked genes below shows the alleles inside the gametes as before.
However, with sex-linked genes the alleles are found on the X-chromosome. A sperm cell can contain either X or y chromosomes and the shape of the blue chromosome represents this. The y chromosome doesn't carry the allele for mid-digital hair: Possible alleles: XH Xh, or y-
Activity 3 - A new hypothesis explains both sets of data.
Human Genetics 3 - Multiple Alleles - another explanation (Word document)
Teachers notes
By following these worksheets students will see how the theory and experiment bring about these advances in our understanding. Students actively build ideas through experience and reflection. This is the constructivist approach.
The old worksheets for activities 1 & 2 an be found here
Only the two Java applets above are required.
Hand lenses - could be useful for looking at hair on fingers.
No other special requirements for this activity.
The develop an understanding of sex linked genes and notation of sex linked inheritance.
Human Genetics 3 - is intended as extension, as are the links below.
A good open ended summative task could be to write an agony aunt reply to "Hairy hand help" explaining the latest understanding of the genetics of mid-digital hair.
Syllabus links
Topic 4 SL Genetics
Alternative Ways