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Tutor profile: Francesco D.

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Francesco D.
Tutor for more than two years
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Questions

Subject: Clinical Lab Sciences

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Question:

Which are the three steps or stages of Polymerase Chain Reactions (PCR)?

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Francesco D.
Answer:

PCR consists of three steps or stages: 1) Denaturing of double helix. We heat the dsDNA molecule in solution to a temperature of 95C for about 15 seconds. This gives it enough time to separate into its individual strands of DNA. 2) Annealing of DNA primers. The heated DNA solution is coded to 54C and the DNA primers are added. The lower temperature will allow for hybridization between the primers and the DNA. One DNA primer anneals to the 3' end of each strand. This is done because DNA polymerase synthesizes in the 5' to 3' direction. 3) Replication of DNA with heat-resistant DNA polymerase. The cooled solution is heated to a temperature of 72C. This is the optimal temperature for a thermophilic DNA polymerase called Taq DNA polymerase. The polymerase begins DNA synthesis on the primer and elongates in the 5' to 3' direction on both ends. After one cycle of PCR, we double the number of molecules. We repeat the cycle again by changing the temperature of solution. After two cycles of PCR, we have a total of four DNA molecules. In general what we need to know is that: 2^n = number of DNA after n cycles.

Subject: Biomedical Science

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Question:

How do single-stranded RNA viruses replicate?

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Francesco D.
Answer:

Viruses, with the help of glycoproteins present in their envelope and recognized by specific host cell receptors, bind to them and fuse their membrane envelope with the cell membrane (endocytosis). Thus, the capsid with the virus genome enters the cell. The capsid is degraded by the action of cellular enzymes and the viral RNA (-) acts as a template for the synthesis of the complementary RNA (+) chain. This complementary RNA acts as an mRNA for the production of the virus capsid proteins and the outer membrane glycoproteins. It also functions as a template for viral RNA synthesis. The capsid proteins surround the RNA, while the glycoproteins are transported through the endoplasmic reticulum to the cell membrane. The viruses exit the cells after germination by enclosing a portion of the cell membrane containing the viral proteins. It is found that animal cells are not destroyed like bacteria during the phage lytic cycle.

Subject: Biochemistry

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Question:

What are the reactions of the citric acid cycle?

Inactive
Francesco D.
Answer:

The cycle begins with the fusion of a four-carbon unit of oxalacetate and a two-carbon unit of the acetyl-CoA acetyl group, whereupon citrate is created and coenzyme A is released (step 1). Because this first reaction leads to the synthesis of citric acid, the course of the reactions we are considering is called the citric acid cycle. The isoacetate is then formed (step 2), which is oxidized decarboxylated. That is, a CO2 molecule is removed to produce a compound of five carbon atoms, the α-ketoglutarate and a NAD + molecule reduced to NADH (step 3). A second oxidative decarboxylation reaction is followed, whereby a compound with four carbon atoms, the acetyl-CoA, is formed and a second NADH molecule is produced (step 4). With these two decarboxylation reactions, essentially the acetyl group that fed the first reaction of the citric acid cycle is removed as CO2, which again yields a compound with four carbon atoms. The following reactions are intended to regenerate the oxalacetate used in the first reaction and thus to form a cyclic course of reactions. Acetyl-CoA contains a high energy bond. Thus, when the acetyl-CoA is converted to electrical (step 5) the high energy bond breaks down and this energy is used to form a GTP (gonanosine triphosphate) molecule from GDP (guanosine diphosphate) and inorganic phosphoric acid (a GTP molecule). energy with an ATP molecule). The succinate is then oxidized to fumarate by simultaneously reducing a FAD molecule to FADH2 (step 6), the fumarate is converted to malate (step 7) and finally from malate regenerating oxalacetate while generating an additional NADH molecule (step 8).

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