Gene expression

In the first step of the expression of gene the gene is transcribed into the RNA. In order to check either the gene is activated or not than for this purpose the gene is introduced into the cell. The scientist Ed southern invented the technique of southern blotting.

The technique of southern blotting is used for the separation of DNA. In this technique the process of gel electrophoresis is involved. In order to separate the RNA molecules we use the technique of northern blotting and this technique also involves the use of gel electrophoresis.

In order to carry out this technique we have to isolate the sample of RNA and then purify the RNA sample. As the RNA is purified it is then moved on the gel in order to separate it out. After this the RNA sample is then transferred to nylon membrane.

As in the gel the single strands of RNA are present the complementary sequences are run the gel and then they join with their complementary sequences to form double stranded molecules. Probes are used in this technique and these probes are single stranded DNA molecules.

The technique of hybridization is used for the detection of mRNA molecules. In this technique the cells are not destroyed. The pores are created in the cells and then probes are introduced into the cells. In this way the location of mRNA is identified.

The steps of the northern blotting can be described as below:

1.      In the first step the sample of RNA is isolated from any tissue or cell type.

2.      The different types of RNA can be isolated and the basis for their separation is size. In the gel the RNA molecules of known sizes are introduced and when the RNA molecules of un known size are introduced than we can find out the sizes of these RNA molecules by comparing them the RNA molecules of known size.

3.      When the gel is prepared than the a membrane made of nylon is placed on this gel. When the process of gel electrophoresis is completed than molecules of RNA will move upward into the nylon membrane by the help of capillary action. This membrane is than heated in the oven at the temperature of 90C so that the molecules of RNA become fixed on the gel.

4.      Than the probes are introduced into the gel and these probes are DNA sequences. These probes are when introduced they are attached with the single stranded RNA molecules.

The similar process can be used to find out the position of DNA and RNA molecules. The process of hybridization is used in other processes like the formation of microarrays and gene chips.

This technique is carried out in the way that single stranded molecules become attached to the solid support and then in the mixture the probes are introduced as these probes are single stranded molecules of DNA or RNA.

These probes than form complimentary base pairing with the single strands that are present in the gel. In order to check the intensity of hybridization process we uses different softwares. This technique can be used for the thousands of the molecules.

The main application of this technique is the gene chip, the function of which is to carry the molecules of DNA and these DNA molecules are for every gene in the organisms. The expression of gene can be find out by using this technique.