lecture 3 - thalassemia

Question 1

What are haemoglobinopathies?

Answer 1

Disorders of haemoglobin

Question 2

What are Mendelian disorders?

Answer 2

When specific mutations in single genes are inherited from either parent and result in a genetic disease

Question 3

What is the most common haemoglobinopathy?

Answer 3

HbS - sicke cell disease

Question 4

What are the 3 classes of thalassemia?

Answer 4

Major, indermedia, minor/trait

Question 5

What is thalassemia major?

Answer 5

Severe thalassemia that causes severe anaemia, abnormal bone development and poor development. Requires transfusion

Question 6

What is the side effect of treatment for thalassemia major?

Answer 6

iron overload/build up in the body from constant transfusion. This leads to systemic problems

Question 7

What is thalassemia intermedia?

Answer 7

less severe form of thalassemia which leads to anaemia, poor bone development.

Question 8

What is thalassemia minor?

Answer 8

Indivduals that carry thalassemia gene mutations/deletions but are clinically unaffected or only have mild anaemia

Question 9

What type of globin is present in foetal haemoglobin?

Answer 9

gamma and alpha

Question 10

Why is alpha thalassemia usually fatal in utero, while beta thalassemia is not?

Answer 10

Foetal haemoglobin has alpha and gamma globin, but beta globin is only synthesised after birth. Thus, an absence of beta is only a problem after birth but an absence/mutation of alpha will be problematic during foetal development.

Question 11

How many alpha-globin genes are there?

Answer 11

2 on chromosome 16 - 4 in total

Question 12

How many beta-globin genes are there?

Answer 12

1 on chromosome 11 - so 2 in total

Question 13

What is thalassemia?

Answer 13

A family of genetic disease resulting in reduced production of either the alpha or beta globin chain of haemoglobin.

Question 14

What is allelic heterogeneity?

Answer 14

The occurrence of more than one allele at a locus that can cause similar phenotypes - e.g. a disease

Question 15

How does thalassemia display allelic heterogeneity?

Answer 15

Multiple different deletions/mutations of the alpha- and beta-globin locus will all lead to a presentation of thalassemia

Question 16

What is locus heterogeneity?

Answer 16

The association of more than one locus/gene with a clinical phenotype

Question 17

How does thalassemia display locus heterogeneity?

Answer 17

thalassemia can result from mutations in either the alpha-globin or beta-globin genes.

Question 18

How many copies of the functioning gene is present in alpha thalassemia minor?

Answer 18

2 or 3

Question 19

How many copies of the functioning gene is present in alpha thalassemia major?

Answer 19

0 or 1

Question 20

How many copies of the functioning gene is present in beta thalassemia?

Answer 20

1 or 0

Question 21

What is the standard treatment for thalassemia major?

Answer 21

blood transfusion

Question 22

What therapy is required to counteract the complications of blood transfusion in patients with thalassemia?

Answer 22

Chelation therapy - to remove excess iron

Question 23

What is the cure for thalassemia?

Answer 23

Bone marrow/stem cell transplant

Question 24

What treatment is used in thalassemia to promote gamma-globin production?

Answer 24

hydroxyurea

Question 25

What are the public health approaches to treating thalassemia?

Answer 25

population screening for microcytic anaemia, and therefore carriers of thalassemia