Many researchers are interested in the transcription of protein-encoding genes in eukaryotes. Such researchers want to study mRNA. One method that is used to isolate mRNA is column chromatography.

Researchers can covalently attach short pieces of DNA that contain stretches of thymines (i.e., TTTTTTTTTTTT) to the column matrix, creating what is called a poly-dT column.

When a cell extract is poured over this column, mRNA binds to the column, but other types of RNA do not.

A. Explain how you would use a poly-dT column to obtain a purified preparation of mRNA from eukaryotic cells. In your description, explain why mRNA binds to this column and what you would do to release the mRNA from the column.

B. Can you think of ways to purify other types of RNA, such as tRNA or rRNA?