Genotyping is the process of determining the genes (genotype) of an individual by examining its DNA sequence with the use of biological assays. To be more accurate than the prior sentence, genotyping is the defining of populations, using DNA sequences, by use of molecular tools such as Restriction Fragment Length Polymorphism Identification of Genomic DNA, Random Amplified polymorphic Detection of Genomic DNA, and Amplified Fragment length Polymorphism detection. Genotyping does not necessarily involve defining the genes of an individual. Current methods of doing this include PCR, DNA sequencing, ASO probes, and hybridization to DNA microarrays or beads. The technology is important in clinical research for the investigation of disease-associated genes.
Due to current technological limitations, almost all genotyping is partial. That is, only a small fraction of an individualís genotype is determined. New innovations or mass-sequencing technologies, promise to provide whole-genome genotyping in the future.
Genotyping applies to a broad range of "individuals" including microorganisms. Viruses for instance, or bacteria, can be genotyped. Genotyping in this context may help in controlling the spreading of pathogens, by tracing the origin of outbreaks. This area is often referred to as molecular epidemiology or forensic microbiology.
The "individuals" can also be human beings. When testing for father-/motherhood for instance, scientists typically only need to look at 10 or 20 genomic regions (like single-nucleotide polymorphism (SNPs) to determine relationship or lack thereof. That is a tiny fraction of the human genome, which consists of three billion or so nucleotides.
When genotyping transgenic organisms, a single genomic region may be all that scientists need to look at to determine the genotype. The mouse is the mammalian model of choice for much of medical research today. A single PCR assay is typically enough to genotype a transgenic mouse.
A tannin is an astringent, bitter plant polyphenolic compound that either binds and precipitates or shrinks proteins and various other organic compounds including amino acids and alkaloids. The astringency from the tannins is what causes the dry and puckery feeling in the mouth following the consumption of unripened fruit or red wine. Likewise, the destruction or modification of tannins with time plays an important role in the ripening of fruit and the aging of wine.
The term tannin (from tanna, an Old High German word for oak or fir tree, as in Tannenbaum) refers to the use of wood tannins from oak in tanning animal hides into leather; hence the words "tan" and "tanning" for the treatment of leather. However, the term "tannin" by extension is widely applied to any large polyphenolic compound containing sufficient hydroxyls and other suitable groups (such as carboxyls) to form strong complexes with proteins and other macromolecules. The compounds are widely distributed in many species of plants, where they play a role in protection from predation, and perhaps also in growth regulation.
Tannins have molecular weights ranging from 500 to over 3,000 (gallic acid esters) and up to 20,000 (proanthocyanidins). Tannins are incompatible with alkalis, gelatin, heavy metals, iron, lime water, metallic salts, strong oxidizing agents and zinc sulfate, since they form complexes and precipitate in aqueous solution.
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