An investigator wants to see whether Gene X is expressed in a particular tissue, and if so how long is its mRNA ( i. e. number of nucleotides). Which of the following procedures can provide all of this information?

There is a laboratory method known as RNA blot or "Northern Blot", which is the procedure employed to detect RNA molecules amid a combination of RNA; examining a sample of RNA from a particular tissue to measure the RNA expression of certain genes.

The "Northern Blot" procedure would provide such information.