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(a) Histone deacetylase
(b) Histone acetylase
(c) RNA polymerase II
(d) TATA binding factor
Answer-A
Description- gene- red pigment
gene is placed near centromere: Inactivated due to position effect variegation. moved to centromere. Hence, produces white colonies. Normally deacetylase represses the gene expression but by the increased production of product could occur.
Q72. In order to prove that liposome can serve as a model membrane (mimicking cellular plasma membrane) and can be used as a target for complement- mediated immunolysis, an experiment as below is designed. To initiate such experiment, hepten- conjugated liposomes are made and loaded with umbelliferyl phosphate(UMP) ; hydrolysed product of UMP is umbelliferone and is fluorescent). Such loaded hapten conjugated liposomes in 10 mM Tris buffered saline,pH 7.4 were mixed with anti hapten antibodies and fresh guinea pigserum (as a source of complement) to induce immunolysis of lipsomal membrane. To quanyify only the membrane lysis component which of the assay sequences below is most appropriate?
(a) Mixture is ultra centrifuged and the supernatant reacted with alkaline phosphatase and fluorescence measured
(b) Mixture is sequentially reacted with phospholipase and alkaline phosphatase followed by fluorescence measurements
(c)Mixture is directly subjected to fluorescence measurement
(d) Mixture is treated with Triton X-100 and fluorescence measured
Answer-A
Description- If the liposomal membrane is lysed, UMP fluorescence will be measured within the supernatant reacted with Alkaline phosphatase.
Q73.A null mutation is created in a gene which is responsible for specific phosphorylation at 6th carbon position of mannose on acid hydrolases occurring in cis-Golgi. The following statements are given towards explaining the effect of this mutation-
(1) The lysosome will be devoid of lysosomal enzymes.
(2) lysosomal enzyme will be secreted out.
(3) Lysosomal enzymes will be get localized in cytoplasm.
which statement or combination of statements will explain the effect of mutation if the acid hydrolases in the mutant do not get degraded?
(a)1 and 3
(b) 2 and 3
(c)n 3 only
(d) 1 and 2
Answer-D
Description-Within cis-golgi an enzyme Glc-N-Ac phosphotransferase is responsible for adding a Glc-N-Ac-1-phosphate residue on the Mannose sugar through the formation of a phosphodiestet bond: Man-phosphate-Glc-N-Ac. Once formed the lysosomal enzymes are translocated to the trans golgi.
Q74.A newly identified sequence was experrimentally tested by in vitro transport assay using a radiolabelled protein containing the sequence to test import into mitochondria. Transport assay was done for a short time with or without membrane potential and after the assay, the mitochondria were either treated on not treated with proteinase K. At the end of the assay the mitochondria were pelleted and total protein of the pellet was isolated and separated on SDS-PAGE and autoradiographed. A representative auto-radiogram is shown below. Based on this experimental data, which of the following statements is not correct?
(A) The protiens goes into the matrix
(b)Not all the added protein was imported
(c) The protein requires membrane potential for import
(d) The protein is associated with the outer mitochondrial membrane
Answer-D
Description- The proteins inserted into mitochondria requires the membrane potential. The presence of proteinase K will be able to degrade the protein outside the mitochondria.
Q75. Acetyl-(Ala)18-CONH2 exists in alpha-helical conformation in solution. Most of the backbone dihedral angles(ᵠ and ᵩ) will be-
(A) -60 degree and -30 degree
(b) 60 AND 3. Degree
(c)-60 and -30 degree(50%) and 60 and 3. degree(50%)
(D)-80 and -120 degree
ANSWER-A
Q76. Enzyme parameters of four isoenzymes is given below-
Isozyme Km micromolar Vmax
A 0.1 15
B 1.5 45
C 4.0 100
D 0.01 10
These isoenzymes are localized in different tissues. In liver the substrate concentration is 0.2 micromolar. The liver isozyme is likely is to be-
(a)A (b) B
(c) C (d) D
Answer-A
Description- Km of an enzyme is the substrate concentration at which the reaction reaches half of its maximum.
At [S] = Km; V=Vmax/2
The Km of an enzyme tends to be similar to the maximum conc. of its substrate so the liver isozyme is likely to be A.
Q77. DNA is not hydrolysed by alkali whereas RNA is readily hydrolysed. This is due to-
(A) The double helix structure of DNA
(B) The presence of uridine in RNA
(C) Due to features observed in RNA such as stem-loop structures
(D) The presence of 2'-OH group in RNA
Answer-D
Q78. Two homologous proteins were isolate from a psychrophile(p) and a thermophile (T). The purified proteins were subjected to denaturation, protease digestion and circular dichroism (CD). Following observations were made-
1. The CD spectra of P and T proteins are identical
2.Their amino acid composition is 95% identical
3. T and P are equally susceptible to proteolysis in the presence or absence of reducing agent
4. T has higher midpoint of thermal denatu ration than P
The reason for enhanced stability in T is due to-
(A) Altered secondary structure
(B) Increased number of disulfieds in T
(C) Increase in water of hydration
(D) Increase in number of salt bridges
Answer-D
Description- The thermophile protein (T) is more stable as compared to psychrophile (P) as it possess large no. of salt bridges.
Q79. Binding of two ligands to their binding proteins were investigated. Following binding isotherms were obtained-
which of the following statement is correct?
(A) A is a obtained with an oligomeric protein and B is obtained with a monomeric protein
(B) B is obtained with protein with positive cooperativity
(C) A and B were obtained by the same protein at two different temperatures
(D) The profile B is not possible
ANSWER-B
Description- According to scatchard Plot, ligand binds specifically and non covalently with the receptor. A receptor may have one or more binding site over itself.
Q80. Which of the following statement best described archaebacteria?
(A) Mostly autotrophic, cell wall contains peptidoglycan, 60S ribosomes, live in extreme environment
(B) Divide by fission not susceptible to lysozyme, live in extreme environments, mostly autotrophic
(C) Not susceptible to lysozyme, contain Golgi and linear chromosomes
(D) Chitinous cell wall, obligate aerobic, circular chromosomes
ANSWER-B
Description- The archaebacteria are the organisms that divide by fission, are not susceptible to lysozyme, can survive at extreme environmental conditioning and mostly these are autotrophic in nature.
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