A researcher has a Trp− auxotrophic strain of E. coliwith a mutation in a single gene. To identify thatmutant gene, she uses a genomic library made from a wild-type version of that same strain to find plasmids that rescue the mutant phenotype. The result issurprising. She recovers 10 plasmids that provide aTrp+ phenotype, but six of the plasmids contain geneX, while the other four contain gene Y. Our scientisthas encountered a phenomenon called multicopysuppression, related to the fact that plasmids are usually present in several copies per bacterium. Becausethe genes in the plasmids are present in more thantheir usual single copy in the bacterial chromosome,more than the usual amount of Protein X or Protein Yis being produced from the plasmids. Sometimes,overexpression of one protein can rescue the mutantphenotype caused by loss of a different protein.Suggest at least two ways that our scientist could determine which of the two genes, gene X or gene Y, actually corresponds to the mutant gene causing theTrp− phenotype.
Bacterial Genomics
The study of the morphological, physiological, and evolutionary aspects of the bacterial genome is referred to as bacterial genomics. This subdisciplinary field aids in understanding how genes are assembled into genomes. Further, bacterial or microbial genomics has helped researchers in understanding the pathogenicity of bacteria and other microbes.
Transformation Experiment in Bacteria
In the discovery of genetic material, the experiment conducted by Frederick Griffith on Streptococcus pneumonia proved to be a stepping stone.
Plasmids and Vectors
The DNA molecule that exists in a circular shape and is smaller in size which is capable of its replication is called Plasmids. In other words, it is called extra-chromosomal plasmid DNA. Vectors are the molecule which is capable of carrying genetic material which can be transferred into another cell and further carry out replication and expression. Plasmids can act as vectors.
A researcher has a Trp− auxotrophic strain of E. coli
with a mutation in a single gene. To identify that
mutant gene, she uses a genomic library made from a wild-type version of that same strain to find plasmids that rescue the mutant
surprising. She recovers 10 plasmids that provide a
Trp+ phenotype, but six of the plasmids contain gene
X, while the other four contain gene Y. Our scientist
has encountered a phenomenon called multicopy
suppression, related to the fact that plasmids are usually present in several copies per bacterium. Because
the genes in the plasmids are present in more than
their usual single copy in the bacterial chromosome,
more than the usual amount of Protein X or Protein Y
is being produced from the plasmids. Sometimes,
overexpression of one protein can rescue the mutant
phenotype caused by loss of a different protein.
Suggest at least two ways that our scientist could determine which of the two genes, gene X or gene Y, actually corresponds to the mutant gene causing the
Trp− phenotype.
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