GRE苏bject Test: Biology : Electrophoresis and Blots
Study concepts, example questions & explanations for GRE Subject Test: Biology
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Example Questions
Example Question #1 :Understanding Other Blots And Gels
Which of the following blots is used to identify known RNA fragments?
Southern blotting
Northern blotting
Eastern blotting
Western blotting
Northern blotting
A Northern blot is very similar to a Southern blot, except it is used to identify RNA fragments rather than DNA fragments. A gel is used to separate the RNA fragments based on size. A radioactive probe can then be used to identify which known RNA sequences have been combined with an RNA fragment.
A Western blot is used to identify protein subunits and fragments. Eastern blots are used to identify protein modifications, such as glycosylation.
Example Question #11 :Electrophoresis And Blots
A cell line was engineered to contain and express a DNA sequence frequently associated with pancreatic cancer, with the hope that the cell line will undergo rapid cell division much like the cancerous cells. You want to test whether or not the cell line is efficiently transcribing this DNA by measuring the quantity of mRNA produced. Which of the following methods would be best suited for testing this?
Western blot
Thin-layer chromatography
Southern blot
Two-photon microscopy
Northern blot
Northern blot
Northern blots are designed to detect the quantity and identity of mRNA transcripts in cells or tissue. Electrophoresis separates RNAs by size, and then hybridization is used to detect the mRNA sequence of interest. Southern blots detect DNA sequences, but give no information about whether they are transcribed or not. Western blots detect proteins, but we are not interested in translation. Neither thin-layer chromatography nor two-photon microscopy would tell us anything about the genetic processes occurring in the cell line.
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