Biochemistry

...

- Bacterial genomes contain multiple copies of rRNA genes, but only single copies of the genes that encode ribosomal proteins. Can you explain this? (5 marks)

Transcription in eukaryotes is achieved by three different type of RNA polymerase, which RNA polymerase I transcribes ribosomal RNAs (rRNAs), RNA polymerase II transcribes RNAs that will become messenger RNSs (mRNAs) and also small regulatory RNAs, and RNA polymerase II transcribes small RNAs such as transfer RNAs (tRNAs). In bacterial all genes are transcribed by a single type of RNA polymerase (Zvelebil & Baum, 2008). Most prokaryotic genes are arranged in groups called operons that are under the control of a single promoter. In operons, the RNA polymerase creates an mRNA copy that encodes multiple genes (Fitzgerald-Hayes & Reichsman, 2010). rRNA are present in many copies and are used to identify different species of bacteria. Bacteria genomes are less complex than human or other eukaryotic genomes. Bacterial transcription and translation can occurs simultaneously in the cytoplasm. Each RNA molecule after transcription is directly incorporated into a ribosome. Therefore, a few copies of rRNA genes are needed to gather large number of ribosomes that the cell requires. The mRNA that can be translated as many times is the transcript of each ribosomal protein gene. Ribosomal proteins only need a fewer genes compared to rRNA due to the amplication of RNA to protein.

References:

Campbell, AK 2015, Regulation of Intracellular Ca2+ By, and Within, Organelles, Intracellular Calcium, John Wiley & Sons, Ltd, UK, pp. 222-251.

Campbell, M and Farrell, S 2015, Biosynthesis of Nucleic Acids: Replication, Biochemistry, Cengage Learning, USA, pp. 271-275.

Chambers, D, Huang, H & Matthew, G 2015, The cell membrane, Basic Physiology for Anaesthetists, Cambridge University Press, UK, pp.13-17.

Cooper, GM 2004, DNA Replication, The Cell: A Molecular Approach, Sinauer Associates, USA, pp. 179-191.

Fitzgerald-Hayes, M & Reichsman, F 2010, DNA in action, DNA and Biotechnology, Elsevier Inc., USA, pp.39-76.

Hillis, DM, Sadava, D, Heller, DC & Price, MV 2012, Cell Membrane and Signaling, Principles of Life, Sinauer Associates, Inc., USA, pp. 78-99.

Lieberman, M & Marks, AD 2013, Transcription: Synthesis of RNA, Marks’ Basic Medical Biochemistry, Lippincott Williams & Wilkins, China, pp. 227-247.

Lodish, H, Berk, A & Zipursky, SL 2000, The DNA Replication Machinery, Molecular Cell Biology, W.H. Freeman, New York, pp. 241-259.

Los, D & Murata, N 2004, Membrane fluidity and its role in the perception of environmental signals, Biochimica et Biophysica Acta (BBA) - Biomembranes, vol. 1666, no. 1-2, pp. 142-157.

Zvelebil, MJ & Baum, JO 2008, The Nucleic Acid World, Understanding Bioinformatics, Garland Science, Taylor & Francis Group, LLC, pp. 3-24.