Question

2. Referring to "Central Dogma of Molecular Biology" give three examples of potential gene expression manipulation; assuming that the effect takes place on a protein level (translational effect), state if your proposed model results in a "gain-of-function", or "loss-of-function" function for each scenario. (9 pts)

Answer 1

Central dogma of mlecular biology is --->

   DNA---------> mRNA-----------> Protein

DNA forms mRNA by transcription, and mRNA is carried to the cytoplasm where with the help of ribosomes and tRNA proteins are synthesized, which is called translation.

The gene expression can be manupulated by recombinant DNA technique. We can introduce a new gene and new expression can be achieved. We can remove a gene which is not desired to prevent its expression. In SCID disease, Adenosine deaminase deficiency is leading to total lack of lymphocytes since birth. A patient of SCID is introduced with gene coding the enzyme resulting gain of function .

Using SiRNA gene silencing can be brought which is also called RNAi (RNA interfering or RNA silencing ) phenomenon. Here mRNA which brings the message for translation is degraded by SiRNA preventing the gene expression. SiRNA can be developed to destroy mRNAs which code for important proteins like enzymes of respiration in nematodes which will prevent translation of the enzyme and death of the nematode. This is loss of fuction.

Epigenetic changes brought near regulatory loci such as enhancer or promoter can change gene expression. Epigenetics is the change in gene expression which is not due to changes in nucleotide sequences. Methylation can stop a gene expression where as acetylation can increase a gene expression. Addition of a methyl to promoter regions of the operon in bacteria will stop the translation of the gene. This is also a loss of function mutation.