Northern Blot is used for:

Ref: Harpers Illustrated biochemistry, 28th ed, ch. 39,pp-393.Explanation:Northern Blot:Similar to the Southern Blot, but used to probe RNA.Can be used to determine mRNA size, e.g., detect differences in the promoter and terminator sites, etc.Can be used to determine if a particular gene is expressed, and if so, how much, in which tissue type, and when is it expressed in the life cycle