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URA3 is often used in yeast research as a "marker gene", that is, a gene to label chromosomes or plasmids. URA3 encodes Orotidine 5'-phosphate decarboxylase (ODCase) , which is an enzyme that catalyzes one reaction in the synthesis of pyrimidine ribonucleotides (a component of RNA ).
URA3, an orotidine-5' phosphate decarboxylase from yeast, is a positive and negative selectable marker. It is required for uracil biosynthesis and can complement URA3 mutants that are auxotrophic for uracil (positive selection).
Auxotrophic genetic markers are often used in molecular genetics; they were famously used in Beadle and Tatum's Nobel Prize-winning work on the one gene-one enzyme hypothesis, connecting mutations of genes to protein mutations. This then allows for biosynthetic or biochemical pathway mapping that can help determine which enzyme or enzymes are ...
The URA3 marker (URA3 blaster method) is an often-used strategy in uridine auxotrophic strains; however, studies have shown that differences in URA3 position in the genome can be involved in the pathogeny of C. albicans. [119] Besides the URA3 selection one can also use the histidine, leucine and arginine autotrophy.
5-Fluoroorotic acid (5FOA) is a fluorinated derivative of the pyrimidine precursor orotic acid.It is used in yeast genetics to select for the absence of the URA3 gene, which encodes the enzyme for the decarboxylation of 5-fluoroorotic acid to 5-fluorouracil, a toxic metabolite. [1]
In yeast and bacteria, OMP decarboxylase is a single-function enzyme.However, in mammals, OMP decarboxylase is part of a single protein with two catalytic activities.This bifunctional enzyme is named UMP synthase and it also catalyzes the preceding reaction in pyrimidine nucleotide biosynthesis, the transfer of ribose 5-phosphate from 5-phosphoribosyl-1-pyrophosphate to orotate to form OMP.
Auxotrophic selection markers that allow an auxotrophic organism to grow in minimal growth medium may also be used; examples of these are LEU2 and URA3 which are used with their corresponding auxotrophic strains of yeast. [7] Another kind of selectable marker allows for the positive selection of plasmid with cloned gene.
Ligation of selectable marker into plasmid vector: this allows for the differential selection of colonies with, or without the marker gene. An antibiotic resistance gene allows the YAC vector to be amplified and selected for in E. coli by enabling E. coli containing the YAC vector to survive in the presence of an antibiotic.