AdvancedEnvironmentalBiotechnologyII.pptVIP

* * * * * * * * * * * * * * * * * * * * * Clusters of Orthologous Groups of Proteins * * Chris S’s tree. Can’t make the fonts larger because I don’t have the raw data. Libraries of Genes More and more genes are being catalogued (cloned, DNA sequence determined, and filed) from a variety of different sources. Many bacterial genomes have been sequenced. A few eukaryote genomes, including human, have also been sequenced. It is possible to use the internet to look collections of genes that have been cloned from several organisms, and find the functions of those genes. Gene Libraries - Library Construction A gene library can be defined as a collection of living bacteria colonies that have been transformed with different pieces of DNA that is the source of the gene of interest. If a library has a colony of bacteria for every gene, it will consist of tens of thousands of colonies or clones. Screening the Library The library must be screened to discover which bacterial colony is making copies of which gene. The scientist must know either the DNA sequence of the gene, or a very similar gene, the protein that the gene produces, or a DNA marker that has been mapped very close to the gene. Library screening identifies colonies, which have particular genes. Growing more Plasmids When library colonies with the desired genes are located, the bacteria can be grown to make millions of copies of the recombinant plasmids that contain the genes. Clones Large insert clones YACs (Yeast Artificial Chromosomes Useful for mapping ~1mb inserts Unstable during construction and propagation Not useful for sequencing BACs (Bacterial Artificial Chromosomes) ~150kb insert Extremely stable and easy to propagate Gold standard for sequencing targets and chromosome-scale maps Cosmids ~50kb insert Extremely stable and easy to propagate Useful for sequencing but too small for chromosome maps Sequence-ready clones Plasmids 1-10kb insert capacity High copy number Easy to sequence bi-directiona