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Avinash S.
If you want any assistance in Biology then you have found a right place. I did my MS in life-sciences and I will be glad to help you.
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Biomedical Science
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Question:

Q 1. How the PCR technique (Polymerase Chain Reaction) is helpful in diagnosis of numerous diseases?

Avinash S.
Answer:

Q 1. How the PCR technique (Polymerase Chain Reaction) is helpful in the diagnosis of numerous diseases? Answer: The PCR machine (Polymerase Chain Reaction) is basically a thermocycler which maintains the variable temperatures required for the amplification of the DNA (deoxyribonucleic acid). The basic requirement to amplify the particular stretch of DNA during PCR is- 1. Primers which will anneal or bind to the particular desired sequence of DNA, DNA template, which could be DNA isolated from the Blood sample, fecal sample, tissue sample. 3. DNA taq polymerase to amplify the particular stretch of DNA, 4. dNTPs (Deoxynucleotide (dNTP) Solution Mix), the subunits which make DNA strand. 5. Magnesium ions a cofactor of DNA taq polymerase. The various types of genetic and pathological diseases can be verified withing hours using the PCR machine. Also, PCR can be used in prognosis of disease like cancer.

Basic Chemistry
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Question:

1. What is a displacement reaction? 2. What causes the liberation of heat when the NaOH is dissolved in H2O?

Avinash S.
Answer:

Q 1. 1. What is a displacement reaction? Answer: A displacement reaction is a type of chemical reaction where a more reactive element replaces a less reactive element from its compound. Example: Reaction between Silver Nitrate AgNO3 and Zinc (Zn) The displacement reactions can be denoted by the formula: A + BC = B + AC Q 2. What causes the liberation of heat when the NaOH is dissolved in H2O? Answer: Reaction between NaOH and water is an Exothermic reaction. Exothermic reactions are those where the heat is released as a result of chemical reaction. The breaking of bonds and formation of new bonds occur during the reaction but in case of Exothermic reaction the amount of energy produced due to bond breakage is high than the energy consumed during new bond formation and thus heat is liberated.

Biology
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Question:

1. What are the stem cells and how they are important to us? 2. What is the mechanism behind diarrhoea caused by Vibrio cholerae?

Avinash S.
Answer:

Q1. What are the stem cells and how they are important to us? Answer: Stem cells are the undifferentiated cells which have the potential to differentiate into numerous types of other cells and same type stem cells multiply to increase their own number. Stem cells based on their differentiation ability can be put into following categories: 1. Totipotent: Totipotent stem can differentiate into all three germ layers e.g. ectoderm, endoderm and mesoderm and also can give rise to extra-embryonic tissues e.g. placenta. 2. Pluripotent: Pluripotent stem cells have the ability to differentiate into all three germ layers mesoderm, ectoderm and endoderm but can’t give rise to extra-embryonic tissue. 3. Multipotent: Multipotent stem cells have the ability to differentiate into multiple but limited lineages of cells e.g. hematopoietic stem cells can give rise to white blood cells (WBCs), red blood cells (RBCs), monocytes etc. 4. Unipotent: Unipotent stem cells are a small population of undifferentiated stem cells that have the ability to differentiate into only one type of cell and are specially localized in every tissue as progenitor stem cells. There are different types of stem cells. further categories of stem cell can be divided into following types: I. Embryonic Stem Cells (ESCs): ESCs are pluripotent, derived from the inner mass of cells of the blastocyst. II. Induced Pluripotent stem Cells (iPSCs): iPSCs are genetically reprogrammed adult somatic cells that have acquired similar properties as normal stem cells, e.g. self-renewal and multiple lineages of differentiation. III. Adult stem cells (ASCs): ASCs are tissue specific and are involved in tissue repairing and maintenance in an adult body Stem cells are involved in wound healing, organ regeneration to an extent, and in future, they hold the promise of treating diseases like Neurodegeneration, problems related to organ transplant. Scientist successfully has generated different types of fully differentiated adult cells using induced pluripotent stem cells and isolated stem cells, which seems to hold the promise of solving problems of regenerative medicine. 2. What is the mechanism behind diarrhea caused by Vibrio cholerae? Answer: Vibrio cholerae is a gram-negative bacterium, belongs to the phylum Proteobacteria and it's well characterized by its comma-shaped appearance seen under the microscope. To cause any disease any pathogen is required to reach an optimum number like one Vibrio cholerae will never be able to cause diarrhea. When the optimum number of the pathogen like Vibrio cholerae is achieved, the genes required to cause pathogenesis or in simple terms the genes required to synthesize toxin(s) are activated. The bacteria senses this optimum number of bacterial population in it's surrounding by a mechanism known as Quorum sensing. Once the optimum number of bacterial (Vibrio cholerae) population is reached, the Vibrio cholerae starts synthesizing cholera toxin which further is released into the enterocytes (intestinal cells) to which the Vibrio was adhered. The cholera toxin is a pentameric structure, have five subunits. The B subunit of the cholera toxin binds to the GM1 ganglioside receptor located on the intestinal cell, triggering endocytosis (uptake) of the toxin. After the toxin is inside the cell, further goes for multiple changes and finally, the A subunit of the toxin enters the cytosol. The A subunit of the toxin activates the G protein of Gs alpha complex (a very important cell signaling molecule) through ADP-ribosylation reaction. This step locks the G protein in its GTP-bound form, irreversibly, which further leads to the incessant activation of adenylate cyclase and thus continous production of cAMP. The high cAMP levels activate the cystic fibrosis transmembrane conductance regulator (CFTR), which in turn triggers a sizeable efflux of ions and water from affected enterocytes, leading to watery diarrhea. Enkephalins, is a type of drug which regulates intestinal secretion by directly acting on enterocytes. The drug binds to the opioid receptor of enterocytes, which inhibit the synthesis of cAMP induced by cholera toxin, thereby directly controlling ion and water loss.

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