Beta Thalassemia and Genetic Counseling

 

Lesia Kaszczak and Uzma Shah

Inspired by their research experience at Mahidol University, Thailand

 

August 2006

 

 

Introduction:  Mr. and Mrs. Kwan are each carriers (heterozygous) for Beta Thalassemia. While neither have any symptoms,  they are concerned because they would like to start a family.  They have come into the Nakhon Pathom Hospital to discuss the probability of their children carrying the disease. As their physician, it is your job to determine the probability of their children being affected and to discuss family planning options with them.

 

 

I.                   Using your knowledge of Mendelian genetics determine the probability of the possible genotypes of the children. Show your work using a Punnett square.

 

 

Mother                                                X                     Father

Hb E/B                                                            B thal (41/41 –TCTT)/B

 

 

Text Box: Probablity of each  Genotype:   1.   2.   3.   4      

Probablity of each  Genotype:

 

1.

 

2.

 

3.

 

4

 

 

 
 

 

 

 

 

II. Use the information from your punnett square and your previous knowledge to fill out the chart on the next page. 
 

Genotype

1.

2.

3.

4.

 

 

Hemoglobin levels:

 

-Normal

-Increased

-Decreased

 

 

 

 

 

 

 

Drawing of RBC’s

 

-size

-shape

-color

-uniformity

 

 

 

 

 

 

 

 

List at least three possible physiological effects to the child

 

 

 

 

 

 

III. Now that you have assessed your patients and the probabilities of affected offspring, discuss the options with them. Would you advise them to have children? Explain why? Would you discourage them from having children? Explain why. Do you have other suggestions for them? Assign each person in your group the role of doctor, mother and father. Prepare a short (3-5 minute) skit of your discussion. You will be presenting your skit in front of the whole class.