Thalassemias

Question 1

Thalassemias affect both quality and quantity of hemoglobin, how is this so?

Answer 1

Quantity:
• Mutated alpha or beta-globin genes are expressed less frequently

Quality:
• Mutations affect function of globin like in sickle cell anemia

Question 2

What genetic defect specifically causes sickle cell disease?

Answer 2

Glutamine is exchanged for a Valine in the 6th residue of Beta-globin

Question 3

In what geographic region are thalassemias most commonly seen?

Answer 3

Band Stretching across:

• Western Europe, and Northwestern Africa all the way across through southern asia

Question 4

In what geographic region are sickle cell anemias most common?

Answer 4

Band Stretching across:

• West Africa through Central Africa

Question 5

In what geographic region are Hemoglobin C disorders most common?

Answer 5

Southwestern Africa

Question 6

You get a mutation affecting blood function what two chromosomes could this have occurred on? (be specific)

Answer 6

Chromosome 16 - Alpha Globin

Chromosome 11 - Beta Globin

Question 7

At birth what type of hemoglobin predominates?

Answer 7

Hemoglobin F - (alpha2, gamma2) , Hemoglobin A (adult hemoglobin - alpha2, beta2) becomes predominant a few weeks after birth

Question 8

How many alpha genes are located on each chromosome?

• What chromosome is this?

Answer 8

2 genes alpha1 and alpha 2 located on chromosome 16

• Each person then has 4 copies of alpha globin genes

Question 9

What types of hemoglobin are seen in alpha thalassemia?

*cases when these are seen?

Answer 9

Alpha Thalessemia 3
• Hemoglobin H - (beta 4)

Hydrops Fetalis (4 defective genes) 
• Hemoglobin Bart's - (gamma4)

Question 10

Suppose you run electrophoresis on a patient with ß-thalassemia, what types of hemoglobin do you expect to see?

Answer 10

ß-Thalessemia
• Increased Hemoglobin F (alpha2, gamma2)
• Increased Hemoglobin A2 (alpha2, delta2)