Inheritable DNA-sequence positions {marker}| are restriction-enzyme cutting sites, fragment-length polymorphisms, genes, minisatellite DNAs, or microsatellite DNAs. Markers have inheritance patterns.
Replicated nucleic acids have added genes {marker gene}, to indicate foreign-DNA insertion and DNA replication.
bacteria
Hosts with added antibiotic resistance genes make proteins that resist antibiotics, whereas hosts with no such genes die. Beta-galactosidase gene makes protein that metabolizes galactose and makes color. Hosts with no beta-galactosidase gene have no color.
yeast
Yeast can grow without leucine if they have LEU gene, without histidine if they have HIS3 gene, without lysine if they have LYS2 gene, without tryptophan if they have TRP1 gene, and without uracil if they have URA3 gene.
plants
Genes {beta-glucuronidase gene} {GUS gene} can make protein that makes glucuronides. Plants have no glucuronides, so E. coli GUS genes can be markers for plants. Firefly luciferase gene makes light. Luciferase genes can be reporter genes for plants.
mammals
Thymidine kinase (tk) gene makes protein that makes thymidine triphosphate {thymidylate}. Mammalian cells (tk-) can have no thymidine kinase gene, so thymidine kinase genes can mark cells (tk+). Aminopterin inhibits all other thymidylate synthesis pathways, so only thymidine kinase gene can make thymidylate.
drugs
G418 inhibits protein synthesis and causes cell death. Aminoglycoside phosphotransferase (APH) gene makes protein that inactivates G418.
Methotrexate inhibits dihydrofolate reductase and causes cell death. Methotrexate-resistant dihydrofolate reductase (DHFR) gene makes protein that resists methotrexate.
Hygromycin-B inhibits protein synthesis and causes cell death. Hygromycin-B-phosphotransferase gene makes protein that alters hygromycin-B.
Mycophenolic acid inhibits GMP synthesis and causes cell death. Xanthine-guanine phosphoribosyltransferase (XGPRT) gene allows GMP synthesis from xanthine.
9-beta-D-xylofuranoyladenine (Xyl-A) damages DNA and causes cell death. Adenosine deaminase (ADA) gene metabolizes Xyl-A.
Replicating nucleic acids can have added genes {reporter gene} that catalyze reactions used to report that promoters are working or not, for gene-expression or transcription-factor studies. For example, chloramphenicol acetyltransferase gene (CAT) reacts with chloramphenicol. Reporter genes are after promoters, to provide direct promoter-activity assays.
4-Genetics-Recombinant DNA-Cloning
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Date Modified: 2022.0225