The other blotting techniques emerged from this method have been termed as Northern (for RNA), Western (for proteins), Eastern (for post-translational protein modifications) and Southwestern (for DNA-protein interactions.
If the probe was labeled with radioactivity, it can expose X-ray film directly.īelow is an example of a real Southern blot used to detect the presence of a gene that was transformed into a mixed cell population. Southern blotting was introduced by Edwin Southern in 1975 as a method to detect specific sequences of DNA in DNA samples. alkaline phosphatase or horseradish peroxidase).Ĥ) The location of the probe is revealed by incubating it with a colorless substrate that the attached enzyme converts to a colored product that can be seen or gives off light which will expose X-ray film. The probe cannot be seen but it is either radioactive or has an enzyme bound to it (e.g. SNOW DROP is for helping you to memorize the different types of blotting techniques on the MCAT. This probe will form base pairs with its complementary DNA sequence and bind to form a double-stranded DNA molecule. The DNA fragements retain the same pattern of separation they had on the gel.ģ) The blot is incubated with many copies of a probe which is single-stranded DNA. The DNA is denature into single strands by incubation with NaOH.Ģ) The DNA is transfered to a membrane which is a sheet of special blotting paper.
Because there are so many different restriction fragments on the gel, it usually appears as a smear rather than discrete bands. It is an analytical technique in molecular biology research that end-users use to measure the size and amount of specific DNA sequences in a complex mixture through immobilization of the target sequence to a solid-support followed by hybridization of a complementary DNA probe. 1) DNA (genomic or other source) is digested with a restriction enzyme and separated by gel electrophoresis, usually an agarose gel. Southern blotting was originally introduced by Edwin Southern in 1975.
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