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Hairy Hands - genetics of mid-digital hair

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  • SL Core /
  • Genetics Activities for Learning/
  • 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

Dear Agony Aunt,
Hey this is really embarrassing for me! i have hair all over the back of my hands and on my knuckles! and it just looks gross is there any thing i can do to get rid of it or make it less noticeable
Signed: Hairy Hands.

Hairy Situation: Teen Magazine Reply to the Hairy Hands

Dear Hairy Hands!,
Unwanted hair is embarrassing for everyone whether you are male or female.
It is normal to have some hair on your hands and knuckles regardless of gender.
It is controlled (at least partly) by your genes.
I'll try to find out more for you.
Signed: Agony Aunt

Activity 1- Experiments to test theories about genetic inheritance

Take on the role of Agony Aunt and find out about the genetics of mid-digital hair.
Carry out some simple experiments to work out the inheritance pattern of mid-digital hair.

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

Complete the activities described on the first worksheet Human genetics 1 - the first sign of madness
(click the eye icon to display)

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.

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

Resources - Web 2.0
Only the two Java applets above are required.
Technician preparation list.
Hand lenses - could be useful for looking at hair on fingers.
No other special requirements for this activity.
Aims
Aims to consolidate student understanding of Punnett squares, phenotype ratios and the scientific method.
The develop an understanding of sex linked genes and notation of sex linked inheritance.
Assessment
Completion of the four word documents will provide evidence of understanding.
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

As a practising teacher I know that activities work best when adapted to student interests and that these are not always the same in every school. Please add your ideas to the comments section below.