Editing Northern blot (section)

==Applications==
Northern blotting allows one to observe a particular gene's expression pattern between tissues, organs, developmental stages, environmental stress levels, pathogen infection, and over the course of treatment.<ref name="Mori1991" /><ref name="Liang1995" /><ref name=Baldwin1999>Baldwin, D., Crane, V., Rice, D. (1999) A comparison of gel-based, nylon filter and microarray techniques to detect differential RNA expression in plants.  Current Opinion in Plant Biol. 2: 96–103.</ref>  The technique has been used to show overexpression of oncogenes and downregulation of tumor-suppressor genes in cancerous cells when compared to 'normal' tissue,<ref name="Streit2009" /> as well as the gene expression in the rejection of transplanted organs.<ref name=Utans1994>{{cite journal | last1 = Utans | first1 = U. | last2 = Liang | first2 = P. | last3 = Wyner | first3 = L. R. | last4 = Karnovsky | first4 = M. J. | last5 = Russel | first5 = M. E. | year = 1994 | title = Chronic cardiac rejection: Identification of five upregulated genes in transplanted hearts by differential mRNA display | journal = Proc. Natl. Acad. Sci. USA | volume = 91 | issue = 14| pages = 6463–6467 | doi = 10.1073/pnas.91.14.6463 | pmid = 8022806 | pmc = 44222 | bibcode = 1994PNAS...91.6463U | doi-access = free }}</ref>  If an upregulated gene is observed by an abundance of mRNA on the northern blot the sample can then be sequenced to determine if the gene is known to researchers or if it is a novel finding.<ref name="Utans1994" />  The expression patterns obtained under given conditions can provide insight into the function of that gene.  Since the RNA is first separated by size, if only one probe type is used variance in the level of each band on the membrane can provide insight into the size of the product, suggesting alternative splice products of the same gene or repetitive sequence motifs.<ref name="Durand1993" /><ref name="Gortner1996" />  The variance in size of a gene product can also indicate deletions or errors in transcript processing. By altering the probe target used along the known sequence it is possible to determine which region of the RNA is missing.<ref name="Alberts2008" />