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Sex Linked Genes

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Sex Chromosomes and Sex Linked Genes.

In this activity students read about the inheritance of colour blindness and hemophilia as examples of sex linkage. Then they make structured notes on the essential points using the structured notes worksheet. Following this twelve exercises test the students' understanding of sex linked genes. The final section gives the faster students some thought provoking reading on the over-simplifications in genetics examples in biology education. As we have learned more about genetics we realise that there are few examples of single genes controlling simple inheritance.

Lesson Description

Guiding Questions

Why do men suffer from sex-linked genetic diseases more than women?

Three examples are colour blindness, baldness, and hemophilia.

Are these genes found on the X-chromosome or the y-chromosome?

Activity 1 Explanations of sex linked inheritance

Using an IB text book or the web links below read about the inheritance of colour blindness and hemophilia as examples of sex linkage.

 

Hemophilia

Hemophilia is a bleeding disorder that slows the blood clotting process. People with this condition experience prolonged bleeding or oozing following an injury, surgery, or having a tooth pulled. In severe...

 Genetics Home Reference
 

Inheritance

Genetics of Pregnancy Encyclopedia Corporation.  X-linked dominant, affected mother.  Genetics of Pregnancy Encyclopedia, 2011. JPEG. National Heart, Lung, and Blood Institute. Inheritance Pattern...

 Hemophilia Genetics
 

Understanding Colour Blindness

Deuteranopia is a form of colour blindness in which a person's eyes are unable to receive the green light part of the colour spectrum. If a person can still see some green light then it is considered...

 www.theinkrag.com

Then make a few brief notes using  Students' structured notes worksheet - Sex linked genes

Activity 2: Simple questions on Sex-linked Genetics

Answer the questions on the worksheet Questions on sex-linked genes below.

Activity 3 Further Reading about genetics.

Read this blog article An embarrassment biology education?  and look at the documents which it links to. They illustrate one of the problems of knowledge in all the natural sciences: as new technology becomes available our understanding increases rapidly and it calls our old ideas into question. Science advances like this, but it often takes time for the old ideas to be superseded by new ones.

Once you have read some of the details, chose one of the 'plenary' tasks in the grid below.

Teachers notes

Activity 1 Explanations of sex linked inheritance

There are many resources which explain the inheritance of gender and also of sex-linked genes. A discussion around the board may be the best explanation for many students. The links on this page provide a good starting point for a "webquest"

The structured notes page guides student to make detailed notes closely matched to the IB guide.

Activity 2 Assessment

The simple questions will only take 10 minutes and are useful to ensure that all the students have understood the basics.

Some model answers sex linked questions model answers

Activity 3 Extension work

Faster students may like to read more about the inheritance of colour blindness and baldness. The story is not as simple as many text books would like us to believe, both conditions are caused by more than one gene. There are many other examples of over-simplifications in biology text books. The examples are useful to illustrate the nature of biological discoveries, and the way that science advances.

The plenary choices could make a good end to the lesson if students feel confident about what they have read.