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Northern Blot

A Northern blot is one of a series of blot techniques used to transfer DNA and RNA onto a carrier for sorting and identification. The Northern blot is used to analyze RNA. Northern blots can be used to determine the size of an mRNA transcript, identify functional variants of a gene and measure the relatedness of species. The Northern blot takes its name from its predecessor, the Southern blot, which was named for biologist Edwin Southern, and has nothing whatsoever to do with direction.

In the Northern blot, a blotting membrane is applied to a gel electrophoreses to get the molecules to transfer from the gel to the membrane. The gel is treated with a formaldehyde hybridization buffer to denature the RNA. The membrane should also be kept moist throughout. After pressure is applied evenly to the membrane, the RNA migrates and sticks to the membrane. Then the membrane is baked or irradiated, permanently attaching the RNA to the membrane.

A hybridization probe (known-sequence single-strand DNA or RNA designed to match the analyzed RNA) is introduced to pair with the blotted DNA sequences; the probe is tagged with fluorescent or chromogenic dyes for identification.

Northern blots are intended to study gene expression through identification and examination of genetic differences.

Web Resources On Northern Blot

Northern Blotting
The Basics: Northern Analysis

Book Resources On Northern Blot

Basic Techniques in Molecular Biology by Stefan Surzycki
An Introduction to Forensic DNA Analysis by Rudin & Inman

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