WEEK 3: GENETICS OF BLOOD DISEASES

Question 1

Outline the normal adult hemoglobin types and their percentages.

Answer 1

HbA HbF HbA2
98% ~1% <2%
2 beta chains, 2 gamma chains, 2 delta chains

Question 2

State the 2 types of thalassemia

Answer 2

Two types exist: α- and β

Classified by number and type of genes abnormal.

Question 3

What happens in Thalassemia?

Answer 3

*Inadequate synthesis of either or
both globin chains.

*The globin chain precipitates in the
erythrocyte causing damage.

Question 4

Describe the Geographic Distribution of Thalassemia.

Answer 4

The Mediterranean, The Middle East, South-East Asia, Southern China and Thailand.

Question 5

Describe thalassemia and Malaria.

Answer 5

β-thalassemia heterozygotes protected against severe
malaria
* α-thalassemia homozygotes and heterozygotes are also
protected
* α-thalassemic children have been seen to have higher
incidence of uncomplicated malaria due to P. vivax at an
early age, which then confers protection to P. falciparum.

Question 6

Describe mechanism of protection conferred by the
thalassemia on Malaria.

Answer 6

*Infected thalassemic RBC may increase expression of surface antigens for binding by IgG and complement.

• Lead to better recognition and opsonization. (Seen in β genotypes)
• Infected RBC have increased susceptibility to phagocytosis by monocytes.

Question 7

Describe sicle cell disease.

Answer 7

An inherited recessive disorder

• RBCs crescent shaped due to mutations on Hb
• Sickled red blood cells block small blood vessels.
• Recurrent painful episodes

Question 8

Describe the geographical distribution of sickle cell anemia.

Answer 8

Common in individuals of African descent (1/10 in US carrier.

Question 9

Outline the consequences of Red Blood
Cell Sickling.

Answer 9

• Occlusion of small blood vessels, causing tissue damage
• Red blood cell lifespan shortened from 120 to 20 days.

Question 10

Outline the Complications of Sickle Cell Anemia.

Answer 10

*Painful crises
* Stroke
* swelling and inflammation of the hands and/or feet
* Sudden pooling of blood in the spleen and liver
congestion.
* Chronic organ damage
* Infections
- encapsulated organisms
- pneumococcus

Question 11

Outline factors influencing Racial and Ethnic Health Disparity.

Answer 11

Education
Employment
Housing
Racism
Health care

Question 12

What is racism?

Answer 12

Prejudice, discrimination, or antagonism directed against someone of a different race based on the belief that one’s own race is superior.

Question 13

What is race?

Answer 13

“Pure races in the sense of genetically homogenous populations do not exist in the human species today … Biological differences between human beings reflect both hereditary factors and the influence of natural and social
environments. In most cases, these differences are due to the interaction of both.”