Tuesday, May 21, 2013

Central Dogma of Bio Informatics and Model organisms

The whole process which involves transcription of DNA to mRNA and translation of mRNA to a functional protein is called the Central Dogma of Bio Informatics. This dogma forms the backbone of Bio Informatics and is represented by following stages.

DNA Replication
The DNA contains the genetic blueprint which is maintained and passed on by a process called replication. Replication is carried out by DNA polymerase.

DNA codes for the production of messenger RNA (mRNA) during transcription. Transcription is carried out by RNA polymerase. The mRNA (messenger RNA) undergoes splicing and migrates from the nucleus to the cytoplasm.

Ultimately, this created mRNA finds its way to a ribosome, where it is translated. In prokaryotic cells, which don’t have nucleus and ribosomes the process of transcription and translation may be linked together. In eukaryotic cells, the site of transcription is usually separated from the site of translation (the cytoplasm), thus the mRNA must be transported out of the nucleus into the cytoplasm, where it can be bound by ribosomes. The mRNA is read by the ribosome as triplet codons. Then RNAs (tRNAs) transferred into the ribosome-mRNA complex, matching the codon in the mRNA to the anti-codon in the tRNA, thus adding the correct amino acid in the sequence encoding the gene. Then the amino acids are linked into the growing peptide chain. Finally, protein will be created according to the processes mentioned before.
So eventually it’s clear that the DNA carries information for proteins which perform many functions in different locations of an organism. Proteins in living organisms perform several functions like biological catalysts, Structural proteins etc. The proteins which perform a catalytic function are known as enzymes. Each functional protein has a specific region known as active site which combines with the substrate. The active site has a unique geometric shape that is complementary to the geometric shape of a substrate molecule, similar to the fit of puzzle pieces. This means that proteins specifically react with only one or a very few similar compounds.

Hence an error in the blueprint (DNA) would cause a change in the geometric shape of the active site of the protein. This results in deactivation of the functional protein thus engaging in termination of a reaction or its function and eventually causing a disease condition.

So the Central Dogma of Bioinformatics acts as the backbone for diagnosis of diseases and for drug designing. To perform this much easier and effectively model organisms are used extensively

Model organisms

A model organism is a simplified system that is accessible and easily manipulated. A model organism is an animal, plant or microbe that can be used to study certain biological processes.

They are used to obtain information about other species including humans that are more difficult to study directly which means the situations where human experimentation would be unfeasible or unethical. Regardless of their obvious differences in size and life style, all these model organisms create proteins that perform the same core functions as in humans

When scientists discover that a particular gene is associated with a disease in humans, one of the first things they typically do is find out what that gene does in a model organism such as mouse. Hence the mouse genome is similarly organized to the human genome and large blocks of genes are even arranged in the same order. This often used extensively to establish disease models by imitating the gene defects seen in humans, and these models can be used to test the efficacy of new drugs.

The model organisms and humans share the similar core functional proteins the geometric shape of the active sites is also similar. Thus the potential drugs which have a complementary geometric shape of the disease causing protein can be used on to the model organisms which would result in a similar conclusion if it is used on to humans. For the final confirmation of the drug can be tested on more related species of humans such as chimpanzee and eventually on humans as well.

Many of the drugs in current use were discovered by experiments conducted in animals and humans. However, many drugs are now being designed with the specific disorder in view. Model organisms play a significant role as a resource in the process of drug designing.