MODULE 13                                                                                Baldness

Is there a genetic basis of male pattern baldness?

Introduction

 As some males mature into adult life, hair loss becomes a reality. Is male pattern baldness hereditary? Most people you ask would answer this question in the affirmative. If so, is this trait inherited from fathers or mothers? Or, can baldness be inherited from either parent?

Explore

 To begin your research, navigate to the link below:

http://www.ncbi.nlm.nih.gov/

On the right side of the page, click on the ‘Genes & Disease’ link. Scroll down the page until you find ‘Male pattern baldness,’ found under the ‘Male-Specific Diseases’ category. Answer the questions below as you read your article.

1. What is the name of the enzyme associated with baldness?
2. What two body organs begin to mature when this enzyme is made?
3. How is this enzyme suspected to lead to baldness?
4. What other kind of organism also produces this 5-alpha reductase?
5. To what chromosome has the gene producing this enzyme been mapped?
6. Use your biology textbook or other resource to determine if this chromosome is an autosome, or sex chromosome.

Under ‘Links’ on the left side of the page, click ‘Genomic view.’  The chromosome marked with the red line indicates the position of this gene. Click on the number below this chromosome. Wow! You’re viewing the map of this chromosome! The specific gene is highlighted in pink. Click on the ‘OMIM’ link to view recent research on the role of this enzyme.

1. Read the ‘Gene Function’ section of this article.  Summarize the inheritance of male pattern baldness inheritance. (Click on the light bulb of the third paragraph will bring you to the original research paper on this question.)

8. What is polygenic inheritance? Use your textbook or other resource to find out.

Reflect

1. Is the chromosome on which the enzyme coding resides passed on by just one sex or both sexes?
2. Can male pattern baldness be inherited from one’s mother?

Apply

1. Based on your findings thus far, what do you think it will take to find a genetic therapy for baldness?
   
   
   
   
   
   
   
2. Interview a family you know that has male pattern baldness. In what way(s) does this family’s incidence of baldness agree with the current research on how this trait is inherited? Or, does this family’s experience with baldness tend to contradict the current research. If so, please explain how.
   
   
   
   

MODULE 13    Answer Key

1. 5-alpha reductase

2. External genitalia and prostate

3. Disturbances in 5-alpha reductase activity in the skin might interfere with hair follicles, resulting in baldness.

4. Plants, dogs, rodents, etc.

5. Chromosome 5

6. Chromosome 5 is an autosome.

7. There is no clear pattern in which male pattern baldness is inherited. Ellis, et al suggest that the trait is polygenic. This implies that other genes also play a role in its inheritance.

8. Polygenic inheritance occurs when the inheritance of a particular trait is controlled by more than one gene. Examples of this are hair and skin color.

9. Both sexes, since Chromosome 5 is an autosome.

10. Yes.

11. Answers will vary, but the idea of finding and understanding the other gene(s) which regulate the activity of 5-alpha reductase in skin cells should be present.

12. Answers will vary; however, the use of data in the answer should be present.