Multiple Choice QuestionsA nerve fibre cannot be stimulated during the absolute refractory period of a previous stimulus because
Sodium permeability remains high
Sodium-potassium pump does not operate
Voltage gated calcium channels remain closed
Potassium conductance remains low
ATP driven pumps hydrolyze ATP to ADP and phosphate and use the energy released to pump ions or solutes across a membrane. There are many classes of these pumps and representatives of each are found in all prokaryotic and eukaryotic cells. Which of the following statements about these pumps is NOT correct?
P-type pumps ate multipass transmembrane proteins which phosphorylate themselves during pumping and involve in ion transport.
F-type pumps normally use the H+ gradient across the membrane to drive the synthesis of ATP.
V-type pumps normally use voltage gradient for transport of small molecules.
ABC tranpsorters primarily pump small molecules across cell membrane.
Mutants of lac Y (Y-) gene of E. coli do not synthesize the lactose permease protein. The following statements refer to the behavior of lac Y- mutants under different experimental conditions.
A. No synthesis of β- galactosidase when Y- cells are induced with lactose.
B. Synthesis of β- galactosidase when cells are induced with lactose.
C. No synthesis of β- galactosidase when cells are induced with IPTG.
D. Synthesis of β- galactosidase when cells are induced with IPTG.
E. The cells induced with IPTG cannot grow in the presence of TONPG (TONPG is a compound, whose uptake is mediated by lactose permease and cleaved by β- galactosidase to release a toxic compound).
F. Cells induced with IPTG can grow in the presence of TONPG.
Which combination of the above statements is correct?
A, D and F
B, C and E
A, C and F
A, C and E
The consequence of this recombination will be the formation of:
A. A dicentric and an accentric chromosome in meiosis I as the chiasmata gets terminated.
B. No dicentric or acentric chromosome but appearance of deletion and duplication in both the chromosomes.
C. All non-viable gamestes.
D. Non-viable gametes from crossover products.
Which of the above statements are correct?
A and B
A and C
A and D
B and C
With reference to lac operon, what will be the phenotype of an E.coli strain having a genotype i-o+y-/F’i+ocz-y+?
Constitutive for both β-galactosidase and lac permease.
Inducible for both β-galactosidase and lac permease.
Inducible for β-galactosidase and constitutive for lac permease.
Constitutive for β-galactosidase and inducible for lac permease.
Phosphatidylserine, an important component of biological membrane, is located in
The outer leaflet but flipflops to the inner leaflet under specific conditions.
Both the leaflets.
The middle of the bilayer
The inner leaflet but flipflops to outer leaflet under specific conditions.
Major disadvantage of using liposome as a targeted drug delivery vehicle is that
It gets internalized by phagocytosis inside lysosomes.
It is very unstable and has low shelf-life.
It gets intercalated in cell membranes.
Its drug entrapment efficiency is very low.
All cytosolic proteins have nuclear export signals that allow them to be removed from the nucleus when it reassembles after
Meiosis
Mitosis
Both mitosis and meiosis
DNA replication
Spematogonial stem cell undergoes extensive metamorphosis to become a spermatozoan. Meiosis leads to the formation of spermatids containing 22 autosomes and one sex chromosome. A male mouse was found in a colony which always produces only female pups upon mating. Which one of the following is a possible reason?
Spermiogenesis was defective.
All spermatogonial stem cells contained only X and no Y chromosome.
Activation of the Y chromosome-linked post-meiotic death-related gene may lead to such a situation.
Activation of the X chromosome-linked post-meiotic death-related gene may lead to such a situation.
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