Normal and abnormal hemoglobin

Question 1

myoglobin binds oxygen best at what concentration?

Answer 1

low oxygen concentration

Question 2

which Hb subunits bind oxygen first?

Answer 2

alpha

Question 3

how does 2,3-BPG affect oxygen affinity?

Answer 3

lowers oxygen affinity (stabilizes T form)

Question 4

how does Hb F differ from Hb A and what is the significance?

Answer 4

1. Hb F has a histidine residue in the beta chain - 2,3-BPG cannot bind as well
2. Hb F oxygen affinity increases - allows oxygen flow from mother to fetus

Question 5

what are the two types of hemoglobinopathies?

Answer 5

1. structural variants

2. thalassemias

Question 6

which Hb variant causes sickle cell disease? what is the result?

Answer 6

1. Hb S
2. deoxygenated Hb polymerizes
3. misshapen cells block circulation

Question 7

definition: sickle cell trait, sickle cell disease

Answer 7

1. trait - heterozygous for Hb S

2. disease - homozygous for Hb S

Question 8

how does hydroxyurea treat sickle cell disease?

Answer 8

increases Hb F

Question 9

Hb C causes what condition? why?

Answer 9

1. hemolytic anemia

2. less soluble than Hb A - precipitates and breaks

Question 10

Hb E leads to what conditions? why?

Answer 10

1. mild thalassemia, microcytosis, hypochromia, mild anemia

2. mutant B globin chain is not synthesized effectively

Question 11

definition: thalassemia

Answer 11

reduced synthesis of either type of chain reduces amount of functional tetramer formed

Question 12

when do alpha thalassemias manifest?

Answer 12

throughout development and all of life

Question 13

how are alpha thalassemias most often generated?

Answer 13

deletion by homologous recombination - misalignment during meiosis because loci look similar

Question 14

1 functional B globin gene / 1 defective B globin gene will cause what symptoms?

Answer 14

1. low MCV
2. low MCH
3. increased Hb A2

Question 15

the best characterized beta thalassemias are caused by what defect?

Answer 15

splicing leading to point mutation

Question 16

what is the initial screen test for hemoglobinopathies?

Answer 16

isoelectric focusing