Final answer:
The Northern blot technique is used to detect and measure mRNA levels in a sample, which indicates gene expression. It involves gel electrophoresis, transfer of RNA onto a membrane, and probing with labeled DNA fragments complementary to the target mRNA.
Step-by-step explanation:
The Northern blot is one of the four directional types of blots, specifically designed to detect and quantify mRNA levels within a tissue or organism sample. This analytic technique is useful for studying gene expression, as the presence and amount of mRNA indicate which genes are actively being transcribed.
After RNA extracts are separated via gel electrophoresis, they are transferred onto a membrane and probed with labeled DNA fragments that are complementary to the target mRNA sequence. The labeled probes allow for visualization and measurement of the specific mRNA, providing insight into the gene expression profile of the sample being studied.
For instance, in the context of human genomic disorders such as sickle cell anemia, Northern blotting is not the best method for detecting polymorphisms. Instead, techniques like Southern blotting would be more appropriate for this purpose as they are designed to detect specific DNA sequences and DNA polymorphisms within the genome. However, if researchers are interested in understanding the expression levels of the hemoglobin gene in different tissue samples, Northern blotting would provide valuable information.