TMJC OCPG Notes

Page 1 of 44 Tampines Meridian Junior College JC2 H2/9744 Biology 2024 Core Idea 2B | 2C 10. Genetics & Inheritance (VII) Organization of Genome & Control of Gene Expression in Prokaryotes SYLLABUS OVERVIEW No. Overarching Idea Topics 1 Core Idea 1 The Cell and Biomolecules of Life Cell – The Basic Unit of Life 2 Biomolecules of Life and Cellular Transport 3 Core Idea 3 Energy and Equilibrium Transformation of Energy – Photosynthesis and Cellular Respiration 4 Core Idea 2 Genetics and Inheritance Genetics and Inheritance (I) – The Cell Cycle 5 Genetics and Inheritance (II) – DNA Replication and Gene Expression 6 Genetics and Inheritance (III) – DNA Mutations and their Consequences 7 Genetics and Inheritance (IV) – Molecular Techniques in DNA Analysis 8 Genetics and Inheritance (V) – Organization of Genome & Control of Gene Expression in Eukaryotes [Includes Core Idea 1D: Stem Cells] 9 Genetics and Inheritance (VI) – Organization and Inheritance of Viral Genomes 10 Genetics and Inheritance (VII) – Organization of Genome & Control of Gene Expression in Prokaryotes 11 Genetics and Inheritance (VIII) - Inheritance 12 Core Idea 3 Energy and Equilibrium Communication and Equilibrium in Multicellular Organisms 13 Core Idea 4 Biological Evolution Biological Evolution 14 Extension Topic A Infectious Diseases Immunity and Infectious Diseases 15 Extension Topic B Impact of Climate Change on Animals & Plants Climate Change – Causes and Impacts on Animals and Plants

Page 2 of 44 NARRATIVES An understanding of Genetics and Inheritance that would help make sense of the transition from molecular to organismal level. Genetics and Inheritance provides the molecular basis to the understanding of how variations in populations arise and this is important in the study of biological evolution. At the cellular level, expression of genes involves cellular structures such as the nucleus, endoplasmic r eticulum and ribosome. Many essential products of gene expression are enzymes involved in biochemical pathways which control physiological functions. As such, mutation of genes may give rise to dysfunctional proteins which in turn could result in diseases. Sickle cell anemia and cancer are raised as examples of a monogenic and a mul ti-genic disease respectively. The following questions should help students frame their learning: • How does the genetic make-up of an organism influence its appearance, behavior and survival? • How can we ensure continuity of human as a species? Heritable information, in the form of DNA (and in some cases RNA), provides for continuity of life Genetic information is stored in an organism’s DNA; expression of genes results in the synthesis of functional products, such as rRNA, tRNA and proteins. These products play a role in intra- and extra-cellular biochemical pathways and influence the physiological processes in organisms. Genomes contain heritable information necessary for continuity of life at all levels: cell, organism and system. This information is stored and passed on to subsequent generations via DNA. Reproduction can occur at the cellular or organismal level; each progeny needs to receive heritable genetic information from its parents. An understanding of how eukaryotic, prokaryotic and viral genomes are organized has implications on how gene expression in organisms is controlled. The genome of prokaryotes typically comprises a large circular chromosome and smaller plasmids. Generally, structural genes, which code for proteins essential for bacteria survival, are found in the main chromosome while genes that confer advantages to bacteria survival in stressful environments are found in the plasmids. Prokaryotes reproduce by binary fission. In addition, genetic material can be transferred between bacteria through transformation, transduction and / or conjugation. This transfer of genetic material gives rise to genetic variation within a bacteria population. LEARNING OUTCOMES Core Idea 2B: Organization of Genomes In addition to a large, circular chromosome, bacteria also have several plasmids. Even though bacteria reproduce asexually, they exhibit great deal of genetic diversity through mutation and genetic transfer. Candidates should be able to: a) Describe the structure and organisation of viral, prokaryotic and eukaryotic genomes (including DNA/RNA, single-/double-stranded, number of nucleotides, packing of DNA, linearity/circularity and presence/absence of introns) d) Outline the mechanism of asexual reproduction by binary fission in a typical prokaryote and describe how transformation, transduction and conjugation (including the role of F plasmids but not Hfr) give rise to variation in prokaryotic genomes. Core Idea 2C: Control of Gene Expression In prokaryotes, operons, like the trp and lac operons, regulate gene expression using repressible and inducible systems. Regulatory genes encode proteins that control transcription of structural genes. Candidates should be able to: a) Explain how gene expression in prokaryotes can be regulated, through the concept of simple operons (including lac and trp operons), including the role of regulatory genes; and distinguish between inducible and repressible systems. (Attenuation of trp operon is not required)

Page 3 of 44 LECTURE OUTLINE 1. Structure and Organization of Bacterial Genome 1.1 Structure of Bacterial Genome 1.2 Organisation of Bacterial Genome 2. Asexual Reproduction through Binary Fission 2.1 Process 3. Genetic Variation in Bacteria 3.1 Transformation 3.1.1 Natural 3.1.2 Artificial 3.2 Transduction 3.2.1 Generalised 3.2.2 Specialised 3.3 Conjugation 4. Control of Gene Expression in Prokaryotes 4.1 Concept of operon 4.1.1 Structure of Operon 4.1.2 Advantages of Operon 4.1.3 Regulatory Gene 4.1.4 Relationship between Operon and Regulatory gene coding for repressor 4.2 Regulation of operon 4.2.1 Negative control 4.2.2 Positive control 4.3 Lac operon – an inducible operon 4.3.1 Context 4.3.2 Structure of the Lac operon 4.3.3 LacI regulatory gene 4.3.4 Control of the Lac operon 4.3.5 Mechanism of Lac operon 4.3.6 Summary on Regulation of Lac operon 4.4 Trp operon – a repressible operon 4.4.1 Context 4.4.2 Structure of Trp operon 4.4.3 TrpR regulatory gene 4.4.4 Control of the Trp operon 4.4.5 Mechansim of Trp operon 4.5 Inducible system vs repressible system 5. Comparison between Prokaryotes and Eukaryotes 5.1 Structure and Organisation of Prokaryotic vs Eukaryotic Genome 5.2 Prokaryotic vs Eukaryotic control of gene expression 6. Glossary TEXTBOOK REFERENCES 1. Biology by Campbell and Reece, 9th Edition, Pages 556-564 and 352-355 2. Biological Science by R.Soper, 3rd Edition. 3. Biology of Microorganisms by Brock Madigan Martinko Parker, 7th Edition

Page 4 of 44 Web-links And Animations Structure and Organisation of Bacterial Genome: Bacterial chromosome compaction https://www.youtube.com/watch?v=30B0wGAID4o Supercoiling of bacterial chromosome https://youtu.be/5hwaDamU-jo Binary fission in bacteria https://www.youtube.com/watch?v=XlCA-cdvSvU Genetic Variation in Bacteria: Artificial Transformation 0:00-1:25 https://www.pbslearningmedia. org/resource/biot11.sci.life.gen. transbact/transforming- bacteria/ Transformation, Transduction and Conjugation https://www.youtube.com/watch? v=7tLV20dk-FM What is a plasmid? https://www.youtube.com/ watch?v=SdqJFA6mOkI Bacterial conjugation https://www.youtube.com/ watch?v=hm8SZaFmlWg Control of Gene Expression in Prokaryotes: Lac Operon http://www.sumanasinc.com/ webcontent/animations/content/ lacoperon.html Lac Operon (highly recommended!) https://www.youtube.com/watch?v=- 4Jr84qyKPo&t=231s

Page 5 of 44 1. Structure and Organisation of Bacterial Genome Core id