Genetics Mini Exam I: Studying the Expression Profile of a Gene

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Genetics Mini Exam I: Studying the Expression Profile of a Gene
2015-09-06 20:32:59
Mini exam
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  1. The human beta-globin genes provide an excellent example of __ 
    A differentially expressed gene is switched on only when __
    At all other times the gene is __
    • differential gene expression
    • the biological information that it contains is needed
    • inactive
  2. With beta-globin genes, the differential expression profile is linked to __, but other genes display __, being active in some cell types but inactive in others
    • development
    • tissue specificity
  3. Knowing in which tissues a newly discovered gene is active often provides the first clue that leads eventually to __
    an understanding of the function of that gene
  4. A gene’s mRNA can be detected by __
    Tissue extracts can be tested for the presence of a particular mRNA by __
    hybridization probing x2
  5. The basis of this technique is the ability of __. This can occur not only between __, but also between __
    The formation of base pair between any two polynucleotides is called __
    • any two complementary polynucleotides to form base pairs with one another
    • ssDNA to form the double helix
    • combinations of one DNA and one RNA strand
    • nucleic acid hybridization
  6. ii. Steps of hybridization:

    1 and 2
    Prepare the sample of RNA from the tissues being studied Spot onto a nylon membraneà RNA in sample becomes bound to membrane
  7. ii. Steps of hybridization:

    Steps 3 and 4
    To determine which samples contain a particular mRNA, the membrane is probed with DNA whose sequence matches that of the gene we are interested in

    It can be a segment of DNA or an oligonucleotide with the same sequence

    Hybridization occurs
  8. The probe must be labeled so it can be detected after hybridization.

    What is one way this can occcur; and, what is a problem with it?
    One way: radioactive phosphorus, which is incorporated into the sugar-phosphate backbone of a DNA molecule, and then analyze via autoradiography, in which a sheet of X-ray-sensitive film is placed over the membrane. The samples that contain hybridized RNA are dark spots Problem: hazardous when disposed
  9. The probe must be labeled so it can be detected after hybridization.

    What is a second way?
    Alkaline phosphatase attached to probe DNA Detection by degradation of phosphatase with luminol, which results in emission of light, which can be recorded on normal photographic film
  10. Expression profiling was used to ID the CFTR gene

    Initially, they identified a candidate gene, one they thought might be the one they were looking for. __ was a test to confirm if it was the CFTR gene
    Expression profiling
  11. What was done to profile the CFTR gene?
    • 1) RNA extracts prepped from various tissues
    • 2) They were probed with a clone of the candidate gene (which was radioactively labeled) 
    • 3) They were developed to show that the probe hybridized with RNA extracts from teh pancreas and nasal polyps