Lecture 11

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Questions and Answers

Which amino acid substitution is responsible for the HbC variant?

Glutamate to lysine at position 6 (correct)

Lysine to glutamate at position 6

Alanine to valine at position 6

Valine to alanine at position 6

What is the main effect of the HbC variant on red blood cells?

It results in a milder hemolytic disorder

It leads to severe anemia

It does not cause RBCs to sickle (correct)

It causes RBCs to sickle

Which region is the HbC variant most common in?

North America

Asia

Europe

West Africa (correct)

Which type of thalassemia is characterized by a reduction or absence of alpha-chain synthesis?

Alpha thalassemia Signup and view all the answers

How many alpha-globin genes are present in a cell?

4 (2 on each chromosome 16) Signup and view all the answers

What is the clinical presentation of alpha thalassemia minor?

Asymptomatic Signup and view all the answers

What are the symptoms of HbH disease?

Hemolytic and microcytic anemia, splenomegaly Signup and view all the answers

Which type of thalassemia is characterized by severe anemia in the fetus and is incompatible with life?

Alpha-thalassemia Signup and view all the answers

How many beta-thalassemia genes are present in each cell?

2 Signup and view all the answers

What is the main difference between beta+ and beta0 mutations in beta-thalassemia?

Beta+ mutations result in reduced beta-globin production, while beta0 mutations result in a complete absence of beta-globin production. Signup and view all the answers

Why are the symptoms of beta-thalassemia more severe than those of alpha-thalassemia?

Beta-chains form hemichromes at a faster rate, making beta-thalassemia more severe. Signup and view all the answers

What are the clinical symptoms of beta-thalassemia major (Cooley's anemia)?

All of the above Signup and view all the answers

What is hereditary persistence of fetal hemoglobin (HPFH)?

A benign condition characterized by significant production of HbF that persists into adulthood. Signup and view all the answers

What is the treatment for severe thalassemia?

Blood transfusions and chelation therapy Signup and view all the answers

What is ZYNTELGO?

A one-time gene therapy for beta-thalassemia that uses the patient's own blood stem cells to add functional copies of beta-globin genes. Signup and view all the answers

Study Notes

HbC Variant and Its Effects

The HbC variant is caused by a substitution of glutamic acid with lysine at position 6 of the beta-globin chain.
This variant primarily leads to the distortion of red blood cells, causing them to become rigid and take on a sickle-like shape, which can impair circulation.

Geographic Prevalence of HbC

The HbC variant is most commonly found in West Africa and among individuals of African descent.

Alpha Thalassemia Characteristics

Alpha thalassemia is characterized by a reduction or absence of alpha-chain synthesis, crucial for hemoglobin function.
Each cell contains four alpha-globin genes, producing the alpha chains of hemoglobin.

Clinical Presentation of Alpha Thalassemia Minor

Typically asymptomatic or mild microcytic anemia is present.
Individuals often have normal life expectancy but may have slight anemia.

Symptoms of HbH Disease

HbH disease features more pronounced symptoms, including moderate to severe microcytic anemia, splenomegaly, and skeletal deformities due to hyperplasia of the marrow.

Severe Thalassemia in Fetuses

Beta-thalassemia, specifically the major form, can lead to severe anemia in the fetus and is often incompatible with life.

Beta-Thalassemia Gene Count

Each cell has two beta-thalassemia genes present, one on each chromosome.

Differences Between Beta+ and Beta0 Mutations

Beta+ mutations allow reduced production of beta-globin, while beta0 mutations lead to a complete absence of beta-globin synthesis, causing more severe symptoms.

Severity Comparison: Beta vs. Alpha Thalassemia

Symptoms of beta-thalassemia are generally more severe due to the critical role of beta-globin in forming adult hemoglobin (HbA), leading to more significant oxygen transport issues.

Clinical Symptoms: Beta-Thalassemia Major

Symptoms include severe anemia, growth delay, jaundice, splenomegaly, and bone abnormalities due to marrow expansion.

Hereditary Persistence of Fetal Hemoglobin (HPFH)

HPFH is a condition where levels of fetal hemoglobin remain high in adulthood, providing some protective effects against sickle cell disease and beta-thalassemia symptoms.

Treatment for Severe Thalassemia

Severe thalassemia often requires regular blood transfusions, iron chelation therapy, and possibly stem cell transplantation.

ZYNTELGO

ZYNTELGO is a novel gene therapy aimed at treating beta-thalassemia by introducing functioning copies of the beta-globin gene to restore healthy hemoglobin production.

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Genetics Lecture 11