Question 1
APC inactivates FVIIIa by proteolytic cleavage at which of the following sites?
A. R313 and/or R512
B. R454 and/or R565
C. R234 and/or R554
D. R336 and/or R562
View Answer
Answer: Option D
Explanation:
APC inactivates FVIIIa by proteolytic cleavage at R336 (A1 domain) and/or R562 (A2 domain). Amino acid substitutions at these positions have resulted in FVIII variants with increased hemostatic efficacy in in vitro and in vivo assays.
Question 2
B domain of FVIII is necessary for the clotting activity.
A. True
B. False
View Answer
Answer: Option B
Explanation:
The above statement is false. Although the B domain of FVIII comprises 40% of the total protein, it is not necessary for the clotting activity of FVIII. Replacement of the B domain by linker sequence has been used for several B domain ‘deleted’ or ‘truncated’ bioengineered FVIII variants.
Question 3
Elimination of disulfide bond between which two amino acid residues within the A3 domain increases FVIII secretion by 2-fold?
A. C1414 and C1456
B. C1123 and C1158
C. C1785 and C1798
D. C1899 and C1903
View Answer
Answer: Option D
Explanation:
Elimination of disulfide bond between C1899 and C1903 (within the A3 domain) through glycine substitutions increases FVIII secretion by 2-fold from mammalian cell culture, this enhancement is speculated to be due to preventing interactions with free thiols that hinder FVIII secretion.
Question 4
Furin Cleavage is necessary for FVIII biological functions.
A. True
B. False
View Answer
Answer: Option B
Explanation:
The above statement is false. Furin Cleavage is not necessary for FVIII biological functions. In a study, where FVIII BDD (B domain deleted factor VIII) was bioengineered to avoid furin processing by deleting the cleavage sequence enhanced FVIII secretion 3-fold.
Question 5
How many alternatively spliced transcripts are produced by factor VIII gene?
A. Five
B. Seven
C. Three
D. Two
View Answer
Answer: Option D
Explanation:
The factor VIII gene produces two alternatively spliced transcripts. Transcript variant 1 encodes a large glycoprotein, isoform a, which circulates in plasma and associates with von Willebrand factor in a non-covalent complex. This protein undergoes multiple cleavage events. Transcript variant 2 encodes a putative small protein, isoform b.
Question 6
Factor VIII predominantly circulates as a homodimer.
A. True
B. False
View Answer
Answer: Option B
Explanation:
The above statement is false. Factor VIII predominantly circulates as a heterodimer of the heavy chain and the light chain bound through non-covalent metal dependent interactions. The heavy chain is composed of the A1-, A2-, and B-domain. The light chain is composed of the A3-, C1-, and C2- domain.
Question 7
In majority of the cases haemophilia A is inherited as an X-linked recessive trait.
A. False
B. True
View Answer
Answer: Option B
Explanation:
The above statement is true. In majority of the cases haemophilia A is inherited as an X-linked recessive trait, though there are cases which arise from spontaneous mutations. It is a genetic deficiency in clotting factor VIII, which causes increased bleeding and usually affects males.
Question 8
Most early gene therapy studies were focused on haemophilia B, despite the fact that haemophilia B accounts for only 20 % of all haemophilia cases.
A. False
B. True
View Answer
Answer: Option B
Explanation:
The above statement is true. Most early gene therapy studies were focused on haemophilia B, despite the fact that haemophilia B accounts for only 20 % of all haemophilia cases. Full length factor VIII cDNA (7 kb) exceeds the packaging capacity of AAV vectors (∼4.7 kb). The full length of factor IX cDNA is ∼1.6 kb.
Question 9
Protein-engineered bypassing agents have the potential to treat bleeding in haemophilia patients with inhibitors.
A. False
B. True
View Answer
Answer: Option B
Explanation:
The above statement is true. Protein-engineered bypassing agents have the potential to treat bleeding in haemophilia patients with inhibitors. Like FVIIIa, these proteins are designed to promote hemostasis through mechanisms that bypass both FVIII and FIX activity.
Question 10
Removing which of the following enzyme cleavage site impedes the A2 dissociation?
A. Rennin
B. Pepsin
C. Furin
D. Thrombin
View Answer
Answer: Option D
Explanation:
Removing the thrombin cleavage site impedes the A2 dissociation. This removal of thrombin cleavage site R740 and R1649 in a B domain truncated FVIII causes the A2 domain to remain covalently bonded through the peptide chain to the A3 domain. Removal of furin cleavage site does not impede the A2 dissociation.
Question 11
Small changes in the amino acid sequence of proteins can have a profound effect on their immunogenicity.
A. False
B. True
View Answer
Answer: Option B
Explanation:
The above statement is true. Small changes in the amino acid sequence of proteins can have a profound effect on their immunogenicity. The potential advantage of bioengineered variants in gene therapy for haemophilia must be balanced against the potential risk of exacerbating the immunogenicity of the transgene.
Question 12
The FVIII heavy chain and light chain dissociate after cleavage by the furin.
A. True
B. False
View Answer
Answer: Option B
Explanation:
The above statement is false. The FVIII heavy chain and light chain do not dissociate after cleavage by the furin The FVIII heavy chain (A1-a1-A2-a2-B) and light chain (a3-A3-C1-C2) remain associated through non-covalent metal-ion-dependent interactions occurring between the A1 and A3 domains.
Question 13
The interaction between FVIII and the Endoplasmic Reticulum (ER) chaperone BiP enhances FVIII secretion.
A. True
B. False
View Answer
Answer: Option B
Explanation:
The above statement is false. The interaction between FVIII and the Endoplasmic Reticulum (ER) chaperone BiP limits the FVIII secretions. Disruption of this interaction through specific FVIII amino acid substitutions enhances FVIII secretion 2-fold from mammalian cell culture.
Question 14
The potency of gene therapy vectors can be enhanced by using bioengineered extended half-life (EHL) FVIII or FIX fusion proteins as transgenes.
A. False
B. True
View Answer
Answer: Option B
Explanation:
The above statement is true. The potency of gene therapy vectors can be enhanced by using bioengineered extended half-life (EHL) FVIII or FIX fusion proteins as transgenes. These EHL products fuse half-lifeextending proteins, such as the IgG1-Fc domain or albumin with FVIII or FIX variants.
Question 15
What is the molecular weight of full length FVIII protein?
A. 170 kDa
B. 210 kDa
C. 310 kDa
D. 280 kDa
View Answer
Answer: Option D
Explanation:
The molecular weight of full length FVIII protein is 280 kDa. Full length FVIII is a large, 280 kDa protein primarily expressed in liver sinusoidal endothelial cells (LSECs), as well as extra-hepatic endothelial cells.
Question 16
Where in the cell does the cleavage of B domain (of FVIII) occurs by protease furin?
A. Endoplasmic Reticulum
B. Mitochondria
C. cis region of golgi apparatus
D. trans region of golgi apparatus
View Answer
Answer: Option D
Explanation:
The cleavage of B domain (of FVIII) occurs by protease furin in the trans region of golgi apparatus. It does not occur in the endoplasmic reticulum, mitochondria, or cis region of golgi apparatus. Proteolytic cleavage of FVIII at R-1313 and/or R-1648 by the trans-golgi protease furin results in heterodimer formation.
Question 17
Which of the following are a successful acute and prophylactic protein bypassing agent for haemophilia with inhibitors?
A. Recombinant FVIa
B. Recombinant FVa
C. Recombinant FVIIIa
D. Recombinant FVIIa
View Answer
Answer: Option D
Explanation:
Recombinant FVIIa is a successful acute and prophylactic protein bypassing agent for haemophilia with inhibitors. Its major efficacy limitation is its short half-life, which is around 2 hours. Recombinant FVIa, recombinant FVa, or recombinant FVIIIa are not successful acute and prophylactic protein bypassing agents for haemophilia with inhibitors.
Question 18
Which of the following can inactivate the activated FVIII?
A. Inactivated protein B
B. Activated protein B
C. Inactivated protein C
D. Activated protein C
View Answer
Answer: Option D
Explanation:
Once activated, FVIIIa is inactivated by the dissociation of the A2-domain from the heterotrimer and/or by the proteolytic inactivation by activated protein C (APC). Activated FVIII cannot be activated by activated/inactivated protein B.
Question 19
Which of the following catalyzes the conversion of prothrombin to thrombin?
A. Platelets
B. Fibrin
C. Pectinase
D. Thromboplastin
View Answer
Answer: Option D
Explanation:
Thromboplastin catalyzes the conversion of prothrombin to thrombin. Platelets, fibrin, or pectinase do not catalyze the conversion of prothrombin to thrombin. Bivalent calcium ions are also required for this conversion reaction.
Question 20
Which of the following clotting factor is deficient in people suffering from haemophilia A?
A. Factor V
B. Factor VI
C. Factor IX
D. Factor VIII
View Answer
Answer: Option D
Explanation:
Factor VIII is the clotting factor that is deficient in people suffering from haemophilia A. Factor V, Factor VI, and Factor IX are not deficient in people suffering from haemophilia A. Haemophilia is a genetic disease, carried by females but only affecting their sons. Queen Victoria was a famous carrier.
Question 21
Which of the following clotting factor is deficient in people suffering from haemophilia B?
A. Factor V
B. Factor VII
C. Factor VIII
D. Factor IX
View Answer
Answer: Option D
Explanation:
Factor IX is the clotting factor that is deficient in people suffering from haemophilia B. Factor V, Factor VII, or Factor VIII are not deficient in people suffering from haemophilia B. Haemophilia B is an X-linked bleeding disorder due to inheritable deficiencies in clotting factor IX.
Question 22
Which of the following domain is the cleavage site for furin enzyme?
A. A domain
B. A2 domain
C. C1 domain
D. B domain
View Answer
Answer: Option D
Explanation:
B domain is the cleavage site for furin enzyme. A domain, A2 domain, or C1 domain are not cleavage sites for furin enzyme. The formation of heterodimer is due to the proteolytic cleavage by the intracellular proprotein convertase furin within the B domain at either R-1313 and/or R-1648.
Question 23
Which of the following enzyme cleaves fibrinogen into fibrin which polymerizes and crosslinks (using factor VIII) into a blood clot?
A. Pepsin
B. Lipase
C. Furin
D. Thrombin
View Answer
Answer: Option D
Explanation:
Thrombin cleaves fibrinogen into fibrin which polymerizes and crosslinks (using factor VIII) into a blood clot. Pepsin, lipase, or furin do not cleave fibrinogen into fibrin which polymerizes and crosslinks into a blood clot.
Question 24
Which of the following factor is also known as an anti-hemophilic factor?
A. Factor VII
B. Factor V
C. Factor VI
D. Factor VIII
View Answer
Answer: Option D
Explanation:
Bloodclotting factor VIII (FVIII) is known as an anti-hemophilic factor. Factor VII, factor V, and factor VI are not known as an anti-hemophilic factor. The blood clotting factor is the nonenzymatic cofactor to the activated clotting factor IX (FIXa). When this is proteolytically activated it interacts with FIXa to form a tight non-covalent complex. This binds to and activates factor X (FX). FVIII gene defects may cause hemophilia A.
Question 25
Which of the following factors require LMAN1-facilitated transport from the ER to the Golgi?
A. FV and FVI
B. FVII and FVI
C. FVI and FVIII
D. FVIII and FV
View Answer
Answer: Option D
Explanation:
FVIII and FV require LMAN1-facilitated transport from the ER to the Golgi, which is dependent on N-linked oligosaccharides that occur mostly in the B domain. FVI and FVII do not require LMAN1-facilitated transport from the ER to the Golgi.
Question 26
Which of the following is a bypassing agent, that circumvents the inhibitor to provide hemostasis?
A. Recombinant factor X (FX)
B. Recombinant factor IX (FIX)
C. Recombinant activated factor VIII (FVIIIa)
D. Recombinant activated factor VII (FVIIa)
View Answer
Answer: Option D
Explanation:
Recombinant activated factor VII (FVIIa) is a bypassing agent, that circumvents the inhibitor to provide hemostasis. Recombinant factor X (FX), recombinant factor IX (FIX), and recombinant activated factor VIII (FVIIIa) are not bypassing agents. Activated prothrombin complex concentrate (aPCC) is also a bypassing agent.
Question 27
Which of the following is not likely to play a role in clotting of blood?
A. Fibrinogen
B. Platelets
C. Clotting factors
D. Antibodies
View Answer
Answer: Option D
Explanation:
Antibodies are not likely to play a role in clotting of blood. Fibrinogen, platelets, and clotting factors are likely to play a role in clotting of blood. The blood has a finely tuned mechanism for forming clots, but only when needed.
Question 28
Which of the following is responsible for the activation of factor X (FX) during sustained coagulation?
A. Activated Factor V (FVa)
B. Activated Factor VIII (FVIIIa)
C. Activated Factor XII (FXIIa)
D. Activated Factor IX (FIXa)
View Answer
Answer: Option D
Explanation:
Activated Factor IX (FIXa) is responsible for the activation of factor X (FX) during sustained coagulation. During coagulation, FVIII is activated mostly by thrombin. Once activated (FVIIIa), it acts as a cofactor for the activated FIX (FIXa). Activated Factor V (FVa), activated Factor VIII (FVIIIa), or activated Factor XII (FXIIa) are not responsible for the activation of factor X (FX) during sustained coagulation.
Question 29
Which of the following mostly activates FVIII during coagulation?
A. Plasmin
B. Furin
C. Fibrin
D. Thrombin
View Answer
Answer: Option D
Explanation:
FVIII is mostly activated by thrombin during coagulation. Once activated (FVIIIa) it acts as a co-factor for activated FIX (FIXa), which is responsible for the activation of factor X (FX). Plasmin, furin, or fibrin do not activate FVIII during coagulation.