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Select the Question mark to the left of each question for the answer.
How is it that Desert Research Institute scientists are working in the ocean in Antarctica?
Why do you need to travel all the way to Antarctica to study Archaeal gene expression?
How do you get from Reno to Palmer Station?
What are the best genetic tools to measure changes in gene expression?
What can gene expression in archaea and bacteria teach us that can lead to great new discoveries?
What is the Tree of Life?

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What are the best genetic tools to measure changes in gene expression? Gene expression is most commonly studied in the laboratory using pure cultures of microorganisms. In recent years there has been a growing interest in taking the study of microbial gene expression to the field. This way we can better understand what they're actually doing (i.e. how they modify and survive) in their true environments.

Very few techniques are available to study microbial gene expression (most have been used only with Eukaryotes):

  1. To study the expression of a single gene, reverse transcriptase RT-PCR is used. This technique can be made quantitative if the researcher wishes.
  2. To obtain a profile of all genes being expressed at a given point there are at least four different methods. Most of these methods (except DNA microarray hybridization) have not seen much application in single-cell organisms due to the fact that there is no simple way to separate rRNA from mRNA (this is quite simple for eukaryotes). Fortunately, technology improving this separation is now becoming available.
  • cDNA library
  • Differential Display (DD)
  • Representation Differentiation Analysis (RDA)
  • DNA microarray hybridization

Briefly, here's how each of these technologies work. cDNA libraries of transcribed mRNAs are sequenced allowing genes expressed to be identified by homology to known sequences. DD and RDA can be used to display the differences in gene expression between two or more samples. Both these methods result in a pool of transcribed genes reverse transcribed to cDNA molecules which are then either visualized by gel electrophoretic techniques, or cloned and sequenced.

DNA microarray hybridizations are a rapidly growing technology in which different genes of interest are arrayed and queried through hybridization analyses (all genes in an entire microbial genome e.g. 4000-5000, can be put on the same array). Such results provide information as to whether the genes of interest are actually expressed (in the form of mRNA) at the time of sampling. DNA microarray technology holds a lot of promise for future microbial studies both with pure cultures and with environmental samples.

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