PCR has been used to diagnose diseases, identify a perpetrator in a crime scene by matching the DNA at a crime scene with suspects, clone genes, and sequence genes. 

Applications of PCR

- PCR is very sensitive – any impurities in the DNA sample can cause errors in the results. 

- Although the PCR primers are designed to be specific to the DNA fragment of interest, they can anneal to pieces of DNA which will cause the PCR to amplify wrong pieces of DNA. Thus, great care must be taken to not contaminate the samples.  


Disadvantages of PCR

There are three broad steps of PCR
- Denaturation 
- Annealing
- Extension 

These steps are repeated as many times as desired to keep synthesizing the DNA fragment desired. 

Steps of PCR

Polymerase chain reaction (PCR) was discovered in 1985. It is technique usedin laboratories that allows for the synthesis of a lot of a specific fragment of DNA 

Grand Valley State University

Nucleotide function

1. Precursors for nucleic acid synthesis: DNA, RNA

2. ATP is the prime energy source for biologic processes, GTP is sometimes used
Molecular motors, active transport of solutes across membranes

3. Nucleotides can activate biomolecules for synthetic reactions: 
 - UTP activating glucose, CTP activating alcohol head groups
 - ATP activation in several reactions

4. Nucleotides and derivatives are important parts of many second messenger systems (Cyclic AMP, cyclic GMP )

5. ATP is a source of phosphate for kinase reactions

Seen in regulation
Glycogen synthesis and degradation
Glycolysis


Nucleotides

Garibyan, L., & Avashia, N. (2013). Polymerase chain reaction. The Journal of investigative dermatology, 133(3), 1–4. 

Polymerase Chain Reaction

THE STRUCTURE OF NUCLEOSIDES
- Ribonucleoside - ribose sugar + base
- Deoxyribonucleoside - deoxyribose sugar + base
 >Adenosine is an example of a nucleoside
 >Deoxyadenosine is a deoxynucleoside

1. Sugar - can have ribose or deoxyribose
2. Nitrogenous bases:
>Purines: Adenine, Guanine
> Pyrimidines: Cytosine, uracil, thymine

Nucleotides are nucleotides plus 1, 2, or 3 phosphates


Nucleosides

- Salvage Pathway (uses recycled bases)
- De Novo Pathway (making bases)

Nucleotide Synthesis

- The breakdown of nucleotides relies on three major classes of enzymes
- Nucleotidases: Convert nucleotides to nucleosides by removing a phosphate group
- Nucleoside phosphorylases: Nucleoside to a free base and ribose 1-P
- Phosphoribomutase (isomerization): Ribose 1-P to ribose 5-P
> Ribose 5-P can be recycled to make more nucleotides


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