G6PD deficiency

Question 1

Where is the G6PD gene found?

Answer 1

X chromosome

Question 2

How many known mutations of G6PD are known?

Answer 2

150 single base mutations

Question 3

What is G6PD? And what is its function in rbcs?

Answer 3

It is a dimeric enzyme which catalyses the first reaction in the pentose phosphate pathway and is the only source of NADPH in RBCs. Therefore it directly controls the balance between oxidised and reduced glutathion

Question 4

Describe the normal genotype for G6PD in males and females

Answer 4

Normally males are hemizygous and females have two copies of the gene - they can normal gene expression or be heterozygous (X-inactivation)

Question 5

In which populations are homozygous females (with mutated G6PD) found?

Answer 5

In populations where the frequency of the mutation is very high

Question 6

What is the name given to G6PD deficiency?

Answer 6

Favism

Question 7

What are the dangers of favism

Answer 7

People may develope hemolytic anemia ; when exposed to oxidant chemicals, they accumulate in the RBC, cause oxidative damage and lyse them

Question 8

How does G6PD confer resistance against Malaria?

Answer 8

When G6PD deficient RBCs are exposed to oxidative stress –> causes metahemoglobin formation, release of ferriheme and premature lysis of the cell (hemolytic anemia). Hence a ‘suicidal infection’ takes place - this impairs parasite multiplication