Sunday 28 February 2021
Friday 26 February 2021
Holocentric chromosomes are :
Q. Holocentric chromosomes are :
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Answer is A). Chromosomes with multiple centromeres
The centromere is the part of a chromosome that links sister chromatids or a dyad. During mitosis, spindle fibers attach to the centromere via the kinetochore. Centromeres were first thought to be genetic loci that direct the behaviour of chromosomes. With holocentric chromosomes, the entire length of the chromosome acts as the centro- mere, Examples of this type of centromere can be found scattered throughout the plant and animal kingdoms, with the most well-known example being the nematode Caenorhabditis elegans.
Which of the following modifications leads to protein degradation ?
Q. Which of the following modifications leads to protein degradation ?
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Answer is D). Ubiquitination
Protein ubiquitination is a dynamic multi- faceted post-translational modification involved in nearly all aspects of cukaryotic biology. Once attached to a substrate, the 76-amino acid protein ubiquitin is subjected to further modifications, creating a multitude of distinct signals with distinct cellular outcomes, referred to as the 'ubiquitin code'. Ubiquitin can be ubiquitinated on seven lysine (Lys) residues or on the N-terminus, leading to polyubiquitin chains that can encompass complex topologies. Ubiquitin is a 76-amino acid protein, and as such bears many potential sites for additional post- translational modifications. The key features of ubiquitin are its seven Lys residues, all of which can be ubiquitinated, to give rise to isopeptide-linked ubiquitin chains.
Wednesday 24 February 2021
cells are produced during the gametophyte stage of a plant's life cycle ?
Q. What special types of cells are produced during the gametophyte stage of a plant's life cycle ?
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Answer is A). Happoid gametes
A gametophyte is a stage in the life cycle of plants and algae that undergo alternation of generations. It is a haploid multicellular organism that develops from a haploid spore that has one set of chromosomes. The gametophyte is the sexual phase in the life cycle of plants and algae. It develops sex organs that produce gametes, haploid sex cells that participate in fertilization to form a diploid zygote in which cach cell has two sets of chromosomes. Cell division of the zygote results in a new diploid multicellular organism, the second stage in the life cycle known as the sporophyte, the function of which is to produce haploid spores by meiosis.
One map unit of one centimorgan corresponds to recombination frequency of:
Q. One map unit of one centimorgan corresponds to recombination frequency of:
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Answer is B). 1%
One genetic map unit (m.u.) is defined as that distance between genes for which one product of meiosis out of 100 is recombinant. Put another way, a recombinant frequency of 1 percent is defined as 1 m.u., and an RF of 6 percent is defined as 6 m.u., and so on. A map unit is sometimes referred to as a centimorgan (CM) in honor of Thomas Hunt Morgan, a pioneer in the field of chromosome mapping.
Infectious proteins are present in :
Q. Infectious proteins are present in :
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Answer is C). Prions
Prion is a term first used to describe the mysterious infectious agent responsible for several neurodegenerative diseases found in mammals, including Creutzfeldt-Jakob disease ( CJD ) in humans. The word itself derives from 'proteinaceous infectious particle' ; it refers to " the initially heretical hypothesis that the infectious agent causing those diseases consists only of protein, with no nucleic acid genome. The prion hypothesis explained why the mysterious infectious agent is resistant to ultraviolet radiation, which breaks down nucleic acids, but is susceptible to substances that disrupt proteins.
An enzyme that relieves torsional strain while double-stranded DNA is being unwound is
Q. An enzyme that relieves torsional strain while double-stranded DNA is being unwound is :
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Answer is B). DNA gyrase
DNA gyrase, or simply gyrase, is an enzyme within the class of topoisomerase ( Type II topoisomerase ) that relieves strain while double - stranded DNA is being unwound by helicase. This causes negative supercoiling of the DNA. The gyrase supercoils (or relaxes positive supercoils) into DNA by looping the template so as to form a crossing, then cutting one of the double helices and passing the other through it before releasing the break, changing the linking number in each enzymatic step. This process occurs in prokaryotes (in particular, in bacteria), whose single circular DNA is cut by DNA gyrase and the two ends are then twisted around each other to form supercoils. Gyrase has been found in the apicoplast of the malarial parasite Plasmodium falciparum, a unicellular eukaryote.
Which of the following incorrectly matches the organelle with it's function ?
Q. Which of the following incorrectly matches the organelle with it's function ?
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Answer is B). Mitochondria - photophosphorylation
The respiratory chain and ATP synthesis in mitochondria or photophosphorylation in chloroplasts demand the controlled flux of electrons. These targets seem to be attacked by nicotine, sanguinarine, ellipticine, gramine, alpinigenine, capsaicine, and a few other alkaloids. A multitude of enzymes exist in animal cells and several alkaloids have been reported that interfere with at least one of them.
The single most abundant protein in animal tissues is :
Q. The single most abundant protein in animal tissues is :
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Answer is B). Collagen
Collagen is the most abundant protein in the animal kingdom, and it accounts for around 30% of the total protein content of the human body, providing strength, integrity, and structure. Collagen is found in all connective tissues, such as dermis, bones, tendons, and ligaments, and also provides for the structural integrity of all of internal organs.
Monday 22 February 2021
which of the following metal constituents of membrane associated protein is involved in respiratory electron transport ?
1. which of the following metal constituents of membrane associated protein is involved in respiratory electron transport ?
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Answer is C). Iron
An electron transport chain (ETC) is a series of complexes that transfer electrons from electron donors to electron acceptors via redox (both reduction and oxidation occurring simultaneously) reactions, and couples this electron transfer with the transfer of protons (H+ ions) across a membrane. This creates an electrochemical proton gradient that drives the synthesis of adenosine triphosphate (ATP), a molecule that stores energy chemically in the form of highly strained bonds. The molecules of the chain include peptides, enzymes (which are proteins or protein complexes), and others. The final acceptor of electrons in the electron transport chain during aerobic respiration is molecular oxygen although a variety of acceptors other than oxygen such as sulphate exist in anaerobic respiration.
Bone marrow transplantation in immune compromised patients can potentially cause :
1. Bone marrow transplantation in immune compromised patients can potentially cause :
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Answer is B). GVHD
Graft-versus-host disease (GVHD) is a significant cause of morbidity and mortality following allogenic haematopoietic stem-cell transplantation and thus the focus of much ongoing research. Despite considerable advances in our understanding of the pathophysiology, diagnosis and predisposing factors for both acute and chronic forms of the disease, a standardised therapeutic strategy is still lacking.
With reference to the bacterial cell wall, which of the following statement is correct ?
1. With reference to the bacterial cell wall, which of the following statement is correct ?
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Answer is D). Both Gram +ve and Gram -ve bacteria possess peptidoglycan but the Gram +ve bacteria lacks outer membrane
Viral replication within cells is inhibited directly by :
1. Viral replication within cells is inhibited directly by :
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Answer is A). IFN-γ
IFN-γ is mainly produced by natural killer (NK) cells, NK T-cells and after antigen stimulation by CD4 T-helper cells and CD2 cytotoxic T cells. Although IFN-γ can under certain circumstances directly inhibit viral replication, its main antiviral capability is derived from its immunostimulatory and immunomodulatory effects. It plays an important role in shaping the adaptive immune response by promoting antigen driven T-cell proliferation and homeostatic control of antigen-specific CTL numbers.
1. .......... express CD3 and CD4 molecules.
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Answer is B) - Th1 and Tc cells
CD3: The CD3 complex is comprised of several molecules associated with the T-cell antigen receptor. It is composed of six polypeptides and is found on all T cells. It provides support for the TCR and is involved in trans-membrane signaling when the TCR is filled.
CD4: CD4 is a 55-kDa molecule belongs to the Ig supergene family with four immuno- globulin-like domains. A cell-surface molecule, CD4 is found in association with the TCR on approximately two-thirds of mature T cells (the T-cell subset known as helper T (Th) cells). CD4 molecules recognize the lateral, nonpeptide-binding portion of MHC class II molecules. The TCRs of CD4+ T cells are "restricted" to the recognition of MHC class-II peptide complexes.
Interaction between ........ are not restricted by MHC molecules.
1. Interaction between ........ are not restricted by MHC molecules.
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Answer is B) - Tc cell and target cell
The major histocompatibility complex (MHC) is a set of cell surface proteins essential for the acquired immune system to recognize foreign molecules in vertebrates, which in turn determines histocompatibility.
Thus, MHC molecules act as restriction factors, and the interaction between T cells and target is said to be "MHC-restricted."
The Class I MHC processing pathway primarily :
1. The Class I MHC processing pathway primarily :
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Answer is A)
MHC class I molecules are one of two primary classes of Major Histocompatibility Complex molecules (the other being MHC class II) and are found on the cell surface of all nucleated cells in the bodies of jawed vertebrates. They also occur on platelets, but not on red blood cells. Their function is to display peptide fragments of non-self proteins from within the cell to cytotoxic T cells; this will trigger an immediate response from the immune system against a particular non-self antigen displayed with the help of an MHC 1 class I protein. Because MHC class I molecules present peptides derived from cytosolic- proteins, the pathway of MHC class I presentation is often called cytosolic or endogenous pathway.
Sunday 21 February 2021
CD8 is a marker of :
1. CD8 is a marker of :
CD8 (cluster of differentiation 8) is a transmembrane glycoprotein that serves as a co-receptor for the T cell receptor (TCR). Like the TCR, CD8 binds to a major histocompatibility complex (MHC) molecule, but is specific for the class I MHC protein. There are two isoforms of the protein, alpha and beta, each encoded by a different gene. In humans, both genes are located on chromosome 2 in position 2p12.
The CD8 co-receptor is predominantly expressed on the surface of cytotoxic T cells, but can also be found on natural killer cells, cortical thymocytes, and dendritic cells. It is expressed in T cell lymphoblastic lymphoma and hypo-pigmented mycosis fungoides
Which of the following is characteristic of B but not T cells ?
1. Which of the following is characteristic of B but not T cells ?
One defining characteristic of B-cells is the presence of membrane immunoglobulin, which T-cells lack. These immunoglobulins are IgMs (μ2L2 "IgG-like" subunits) and IgD, they are anchored in the cell membrane through a specialized C-terminal domain of the heavy chain, and they function as the cells' antigen-specific receptors. Memory B-cells bear membrane-bound isotypes other than IgM, representing whatever Ig the cell will begin secreting upon antigenic stimulation.
Cell with specific killing effects :
1. Cell with specific killing effects :
Cytotoxic T-lymphocyte: AT cell that is antigen-specific and is able to search out and kill specific types of virus-infected cells. When cytotoxic T-lymphocytes (CTLS) find cells carrying the viral peptide they are looking for, they induce these cells to secrete proteins that attract nearby macrophages (a type of white blood cells). These macrophages then surround and destroy the infected cells. CTLS are important in the body's response to viruses and cancer. CTLS expresses the CD8 transmembrane glycoprotein and are therefore also known as CD8+ T cells or CT cells.
1. The process of using microorganisms and plants to break down or recycle environmental pollutants is called :
Bioremediation is a natural process that involves the use of biological entities to neutralize the contaminated site. According to the United States EPA, bioremediation is a "treatment that uses naturally occurring organisms to break down hazardous substances into less toxic or non toxic substances". Technologics can be generally classified as in situ or ex situ. In situ bioremediation involves treating the contaminated material at the site, while ex situ involves the removal of the contaminated material to be treated elsewhere. Some examples of bioremediation related technologies are phytoremediation, bioventing, bioleaching, landfarming, bioreactor, composting, bioaugmentation, rhizofiltration, and biostimulation.
In prokaryotes, the lagging strand primers are removed by :
1. In prokaryotes, the lagging strand primers are removed by :
DNA polymerase III will then synthesize a continuous or discontinuous strand of DNA, depending if this is occurring on the leading or lagging strand (Okazaki fragment) of the DNA. DNA polymerase III has a high processivity and therefore, synthesizes DNA very quickly. This high processivity is due in part to the β-clamps that "hold" onto the DNA strands.
Which of the following protein complex involved in breakdown of water ?
Q. Which of the following protein complex involved in breakdown of water ?
An early sign of heat stress to photosynthetic machinery is the damage in photosystem II (PSII) reaction center housed in the thylakoid membranes of the chloroplasts. The PS II complex is the first protein-pigment complex involved in the light-dependent reactions of photosynthesis and is responsible for splitting water into hydrogen and oxygen, as well as generating electrons for transport to other photosynthetic machinery and generating hydrogen ions to create the proton gradient needed for ATP synthesis.
Which of the following techniques is used for quantification of mRNA?
Q. Which of the following techniques is used for quantification of mRNA?
The quantitative RT-PCR is a method used to quantify mRNA levels. This technique is particularly useful to quantitate expression levels of transcripts that are expressed at very low levels, such as GTs. Real-time RT-PCR has gained popularity not only in quantifying gene expression but to confirming differential expression of genes detected by microarray analysis. Real-time RT-PCR uses commer- cially available fluorescence-detecting thermal cyclers to simultaneously amplify specific DNA sequences and measure their concentration. This method is optimal for measuring DNA concentration over a wide dynamic range, its sensitivity is high, and many samples can be processed simultaneously.
Codons that specify the same amino acid often differ in the :
1. Codons that specify the same amino acid often differ in the :
Most amino acids in proteins are specified by more than one codon (i.e. the genetic code is degenerate). Recognition of these codons often occurs using different tRNAs (with corresponding anticodons to these codons) that bind the same amino acid (isoaccepting tRNAs). In addition, codons that specify the same amino acid (synonyms) often differ only in the third base, the wobble position, where base pairing with the anticodon may be less stringent than for the first two positions of the codon, allowing one tRNA to recognize more than one codon.
1. Blood stains are found at the site of a murder. If DNA fingerprinting technique is to be used for identifying the criminal, which of the following is ideal for use?
Forensic science is a specialism that aims to help judges and juries solve legal issues, not only in criminal law but also in civil cases. Over the past 20 years, however, one particular biological tool has revolutionized forensic investigations - the analysis of DNA.
As all living things contain DNA, and all DNA exhibits variability both among and within species, any biological material associated with a legal case carries in it information about its source. Blood stains are found at the site of a murder leukocytes is used. If DNA fingerprinting technique is to be used for identifying the criminal.
Which of the following is the correct order of basic forces in decreasing strength ?
Q. Which of the following is the correct order of basic forces in decreasing strength ?
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Answer is A)
Gravitational Force : The gravitational force is weak, but very long ranged. Furthermore, it is always attractive. It acts between any two pieces of matter in the Universe since mass is its source.
Weak Nuclear Force : The weak force is responsible for radioactive decay and neutrino interactions, It has a very short range and as its name indicates, it is very weak. The weak force causes Beta decay i.e., the conversion of a neutron into a proton, an clectron and an antineutrino.
Electromagnetic Force : The electromagnetic force causes electric and magnetic effects such as the repulsion between like electrical charges or the interaction of bar magnets: It is long-ranged, but much weaker than the strong force. It-can be attractive or repulsive, and acts only between pieces of matter carrying electrical charge. Electricity, magnetism. and light are all produced by this force.
Strong Nuclear Force : The strong interaction is very strong, but very short-ranged. It is responsible for holding the nuclei of atoms together. It is basically attractive, but can be effectively repulsive in some circumstances. The strong force is 'carried' by particles called gluons; that is, when two particles interact through the strong force, they do so by exchanging gluons. Thus, the quarks inside of the protons and neutrons are bound together by the exchange of the strong nuclear force. The following table summarizes the strengths and other important properties of the four fundamental forces.
Antibodies qna
1. Which class of B cell receptors is expressed in naive B-cell ?
Naive B-cells have only mIgM; as they mature, they express both mIgM and mIgD.
2. Which of the following groups of antibodies can cross placenta?
Immunoglobulin G ( IgG ) is a type of antibody. Each IgG has two antigen binding sites. Representing approximately 75 % of serum antibodies in humans. IgG molecules are created and released by plasma B cells. IgG are also involved in the regulation of allergic reactions.
According to Finkelman , there are two pathways of systemic anaphylaxis : antigens can cause systemic anaphylaxis in mice through classic pathway by cross-linking IgE bound the mast cell FcεRI, stimulating the release of both histamine and platelet activating factor (PAF). In the Alternative pathway antigens form complexes with IgG, which then cross-link macrophage FcγRIII and stimulates only PAF release.
3. No antibody activity associated with
IgD activity is still unknown.
4. J chain or joining chain is found in ?
IgM is pentameric antibody molecule and IgA is dimeric antibody molecule, both of these antibodies posses J chain .
5. In the normal human being the concentration(s) of various antibodies in the serum is/are in the order
IgG is the most abundant antibody present in the serum it accounts 70-75% of total antibodies. IgA accounts 15% of total antibodies of serum. IgM account 5-10% of total antibodies of serum. IgE accounts in a normal individual are only 0.05% of total antibodies.
amino acid qna
1. Which of the following enzymes catalyses the attachment of an amino acid to t-RNA ?
aminoacyl tRNA synthetase also calld tRNA ligase which catalyses the attachment of an amino acid to tRNA.
2. which part of an amino acid is always acidic in nature ?
carboxyl (COOH) group of an amino acid is always acidic.
3. Which of the following is not attached to the central carbon atom of an amino acid
The central carbon atom of an amino acid is attached with an amino group(NH₂), caboxyl group(COOH), R side chain and hydrogen atom. there is no any Oxygen molecule which attached with central carbon atom .
4. which one of the following amino acids possesses a net charge at pH 7 ?
Because of the presence of an carboxy group in the side chain, the dicarboxylic (also called acidic) amino acids, aspartic acid exhibit a net negative charge at pH 7; these forms of the amino acids is called aspartate.
5. Which of the following amino acids actually has a secondary amino group ?
Proline is the only amino acid in which the side chain loops back to reattach to the main polypeptide chain. This has two main consequences:
1). Proline has a secondary amino group instead of the primary amino group present in all the other amino acids. It thus behaves differently in many of the reactions used in protein chemistry.
2). Proline forces a bend in the polypeptide backbone and can thus disrupt an a - helix and axert other constraints on the folding of a protein.
Which of the following is a correct statement of the Beer-Lambert law ?
Q. Which of the following is a correct statement of the Beer-Lembert law ?
The absorbance of a compound in solution is directly proportional to both, its concentration and the path length of the cuvette.
The absorbance of a sample is directly proportional to the path length (d), i.e., the thickness of the cuvette in cm, and the concentration (c) of the absorbing species. The relation is expressed by the Beer-Lambert law: A = α cd
The proportionality constant a is specific to a molecular species at a given wavelength and is called the extinction coefficient and has the unit Lg-1 cm-1. It can be calculated from Eq.( i ), if the concentration c is given in gL-1. In analytical chemistry, we often refer to the molar extinction coefficient (ε) (also referred to as the molar absorptivity), given in L mol-1 cm-1. The Beer-Lembert law can be re-written with c in mole L-1. A = ε cd
Beer's law states that ...
Q. Beer's law states that ...
Lambert's law states that the proportion of light absorbed by a material is independent of the intensity of the incident radiation. Beer's law states that the absorbance of a sample is directly proportional to the concentration of the absorbing species. The combination of these two laws gives the expression: A = ε c l
where A is the absorbance, ɛ is the molar absorption coefficient, c is the concentration and l is the path length. The Beer-Lambert law brings together into an equation that which relates the absorbance with the sample concentration (c), the sample thickness (path length, I) and the inherent absorption capability (molar absorptivity, ɛ). The size of the molar absorptivity (or extinction coefficient in the old terminology) is an indication of how sensitive an analysis will be, since, the more a molecule is capable of absorbing light, the smaller the amount of the material we will be able to detect. Molar absorptivity has the units M-1 cm-1, since the product ɛcl must be dimensionless.