Figure 7.4. Northern hybridization.

Figure 7.4Northern hybridization

An RNA extract is electrophoresed under denaturing conditions in an agarose gel (see Technical Note 4.4). After ethidium bromide staining, two bands are seen. These are the two largest rRNA molecules (Section 3.2.1) which are abundant in most cells. The smaller rRNAs, which are also abundant, are not seen because they are so short that they run out of the bottom of the gel and, in most cells, none of the mRNAs (the transcripts of protein-coding genes) are abundant enough to form a band visible after ethidium bromide staining. The gel is blotted onto a nylon membrane and, in this example, probed with a radioactively labeled DNA fragment. A single band is visible on the autoradiograph, showing that the DNA fragment used as the probe contains part or all of one transcribed sequence.

From: Chapter 7, Understanding a Genome Sequence

Cover of Genomes
Genomes. 2nd edition.
Brown TA.
Oxford: Wiley-Liss; 2002.
Copyright © 2002, Garland Science.

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