One very simple way of isolating mRNA from eukaryotic cells is to lyse them, cen

Question

One very simple way of isolating mRNA from eukaryotic cells is to lyse them, centrifuge out the particular (undissolved) material, and then mix the supernatant with small beads coated with many copies of a single stranded DNA sequence. After allowing to mix with the cellular supernatant for a few minutes, the beads can be can be centrifuged and cellular mRNA will be attached to the beads. To liberate the mRNA from the beds, one only has to add a high salt buffer.

First, what is the DNA sequence on the beads?

Second, do all mRNAs bind to the beads or it is specific to only one kind of mRNA?

Third, how does the high salt buffer cause the mRNA to disassociate from the beads?

Explanation / Answer

a)

The described process is called microarray analysis, DNA microarray is used to study the rate of gene expression (synthesis of mRNA) in the cell under given set of conditions. The DNA sequence on the beads is called Single stranded cDNA or complimentary DNA, which is absolutely, binds to specific mRNAs. These DNA sequences are also called probes.

b)

A specific mRNA binds to its specific bead with its opposite complimentary sequence containing probe.

c)

The mRNA has negative charge and the High salt buffer also has negative charge. The High salt buffer binds to positively charged beads and displaces the negatively charged mRNA form beads. This principle is called charge displacement.

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