Question

6. A bacterium does not want to waste energy synthesizing the amino acid arginine if arginine is present in its diet. Therefore, when arginine is present, it activates a repressor protein to prevent transcription of genes that code for enzyme to make arginine. This is an example of what type of regulation? Please describe the mechanism of this regulation.

7. Prokaryotic genetic information transferring processusually acts as target of antibiotics. We observed a new compound with antibiotic action, and we have already proved this compound do not affect the bacterial replication process. Based on your knowledge about gene information transmission (DNA replication, transcription and translation), please assume the possible mechanism(s). Please use your knowledge to make an experiment to prove your assuming?

8. The initiation of transcription in eukaryotes is a key pointof gene expression regulation. The interaction between biological macromolecules (protein-protein, protein-nucleotide) is very important in the expression regulation of eukaryotic genes. Can you give two examples of regulatory mechanisms related to transcription initiation? Describe the structural features of the molecules.

Choose one or two of this questions to which you are the most certain. thanks!!!

Answer 1

6. Biosynthesis of arginine is an anabolic process and in most prokaryotes this process is under repressible negative regulation. The arginine operon produces enzymes which are responsible for synthesis of arginine when it is absent in the medium. A repressible protein is responsible for the regulation of expression of arginine operon. In absence of arginine when the repressible protein when synthesized, it is in inactive form and hence it cannot bind to operator. The operator is free, so the RNA polymerase will bind to promoter region and initiate the transcription of arginine operon. The enzymes will be produced which will catalyse the synthesis of arginine amino acid. A bacterial cell will not waste energy to synthesize enzymes to make an essential amino acid arginine when it is present in the growth media. When arginine is present it acts as a corepressor and will bind to inactive repressor protein and convert it into active form. The active repressor protein then binds to operator and blocks binding of RNA polymerase to the promoter region. Thus the transcription is inhibited and no enzymes will be expressed.