Q-91. In dividing cells, spindle is formed by
a) Ubiquitin
b) Tubulin
c) Laminin
d) Keratin
Answer: Tubulin
Explanation:
Microtubules are necessary for the formation and function of mitotic spindle.
Microtubules are cylinders of 13 longitudinally arranged proto-filaments, each consisting of dimmers of alpha and beta tubulin.
Q-92. The collagen triple helix structure is not found in:
a) Cytoplasm
b) Golgi apparatus
c) Lumen of endoplasmic reticulum
d) Intracellular vesicles
Answer: Cytoplasm.
Explanation:
Synthesis of collagen: RER-> GB-> Intra-cellular secretory vesicles-> Extra-cellular space
Collagen is the major insoluble fibrous protein in the extracellular matrix and in connective tissue.
Its fundamental structural unit is a long (300-nm), thin (1.5-nm-diameter) protein that consists of three coiled subunits: two alpha 1 (I) chains and one alpha 2 (I). Each chain contains precisely 1050 amino acids wound around one another in a characteristic right-handed triple helix.
Q-93. The following separation technique depends on the molecular size of the protein
a) Chromatography on a carboxy-methyl cellulose column
b) Iso-electric focusing
c) Gel filtration chromatography
d) Chromatography on a diethylaminoethyl (DEAE) cellulose column
Answer: Gel filtration chromatography
Explanation:
Molecular separation of two proteins with same charge can be done by gel diffusion chromatography.
Gel diffusion chromatography is the best method to differentiate proteins.
Q-94. The conversion of an optically pure isomer (Enantiomer) into a mixture of equal amounts of both Dextro and Levo forms is called as
a) Polymerization
b) Stereo-isomerization
c) Racemization
d) Fractionation
Answer: Racemization
Explanation:
Racemization is the process in which one enantiomer of a compound converts to the other enantiomer.
The conversion of an optically pure isomer (Enantiomer) into a mixture of equal amounts of both Dextro and Levo forms is called as Racemization. Such mixture is optically inactive and said to be racemic mixture.
Q-95. Decreased glycolytic activity impairs oxygen transport by hemoglobin due to
a) Reduced energy production
b) Decreased production of 2, 3-bisphsphoglycerate
c) Reduced synthesis of hemoglobin
d) Low levels of oxygen
Answer: Decreased production of 2, 3-bisphsphoglycerate
Explanation:
Decreased glycolytic activity-> Decreased level of 2, 3-bisphsphoglycerate-> Shift the oxy-hemoglobin curve to left-> Increased oxygen affinity of hemoglobin-> Decreased released of oxygen to tissue from hemoglobin-> Impairs oxygen transport
Important point:
2, 3-bisphsphoglycerate is produced by an alternative pathway in glycolysis.
Q-96. An enzyme involved in the catabolism of fructose to pyruvate in the liver is
a) Glyceraldehyde-3-phosphate dehydrogenase
b) Phospho-glucomutase
c) Lactate-dehydrogenase
d) Glucokinase
Answer: Glyceraldehyde-3-phosphate dehydrogenase
Explanation: Glyceraldehyde-3-phosphate dehydrogenase
Q-97. Beta-oxidation of odd-chain fatty acids produces
a) Succinyl CoA
b) Propionyl CoA
c) Acetyl CoA
d) Malonyl CoA
Answer: Propionyl CoA
Explanation:
End product of beta oxidation of even chain fatty acids: Acetyl Co-A.
End product of beta oxidation of odd chain fatty acids: Propionyl Co-A.
Q-98. The protein rich in basic amino acids which functions in the packaging of DNA in chromosomes is?
a) Histone
b) Collagen
c) Hyaluronic acid binding protein
d) Fibrinogen
Answer: Histone
Explanation:
Histone:
These small proteins are positively charged at physiologic pH as the result of their high content of basic amino acids like lysine and arginine.
Because of their positive charge, they form ionic bond with negatively charged DNA.
Histones, along with positively charged ions such as Mg++, help neutralize the negatively charged DNA phosphate groups.
Important point:
There are five classes of histones, designated H1, H2A, H2B, H3 and H4.
Q-99. Which of the following is not a post transcriptional modification of RNA?
a) Splicing
b) 5’ Capping
c) 3’ Poly-adenylation
d) Glycosylation
Answer: Glycosylation
Explanation:
Post transcriptional modification of eukaryotic m-RNA:
5’ Capping
Addition of poly-A tail
Removal of introns
Alternative splicing of m-RNA molecules
Q-100. Restriction fragment length polymorphism is used for
a) Analysis of chromosome structures
b) DNA estimation
c) Synthesis of nucleic acid
d) Detecting proteins in a cell
Answer: Analysis of chromosome structures
Explanation:
Restriction fragment length polymorphism or RFLP analysis is used to identify a change in the genetic sequence that occurs at a site where a restriction enzyme cuts.
RFLPs can be used to trace inheritance patterns, identify specific mutations, and for other molecular genetic-techniques.
Restriction enzymes recognize specific short sequences of DNA and cut the DNA at those sites.