TMJC DNA Rep & Gene Exp Notes

1 Biology Unit, Tampines Meridian JC Tampines Meridian Junior College JC1 H2/9744 Biology 2023 Core Idea 2A 5. Genetics & Inheritance (II) – DNA Replication & Gene Expression 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 Complete the pre-lecture exercise on pg 5

2 Biology Unit, Tampines Meridian JC TOPIC SYNOPSIS 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 some examples of genetic diseases. The following questions should help you frame your learning: • How does the genetic make -up of an organism and the environment influence the organism’s appearance, behavior and survival? • How does the inheritance of genetic information ensure the continuity of humans as a species? Heritable information, in the form of DNA (and in some cases RNA), provides for continuity of life 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 pr ogeny needs to receive heritable genetic information from its parent(s). The process of replication is thus vital to ensure that such genetic information is passed from the parents to the offspring. Genetic information is stored in an organism’s DNA; exp ression 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. But how does a gene, which consists of a string of DNA hidden in a cell's nucleus, know when it should express itself? How does this gene lead to the production of a string of amino acids called a protein? How do different types of cells know which types of proteins they must ma nufacture? The answers to such questions lie in the study of gene expression. This topic begins by showing how a quiet, well- guarded string of DNA is expressed to make RNA and how the messenger RNA is translated to form a protein. Along the way, the article set also examines the nature of the genetic code, how the elements of code were predicted, and how the actual codons were determined.

3 Biology Unit, Tampines Meridian JC LEARNING OUTCOMES Core Idea 2A: The Structure of Nucleic Acids and Gene Expression The structure of DNA was proposed by Watson and Crick in 1953. With an understanding of DNA structure, experimental evidence supported the proposal that DNA replicates in a semi -conservative manner. The central dogma states that genetic information is encoded in the DNA and transf erred to the mRNA during transcription. In addition to mRNA transcription, tRNA and rRNA are transcribed; tRNA is needed during translation while rRNA is a component of ribosomes. In eukaryotic transcription, pre-mRNA is synthesised and then processed to p roduce mature mRNA. Subsequently, through translation, the information on the mRNA is used to synthesise polypeptides, which are folded into functional proteins. Candidates should be able to: a) Describe the process of DNA replication and how the end replication problem arises. b) Describe how the information on DNA is used to synthesise polypeptides in prokaryotes and eukaryotes. (Description of the processes of transcription, formation of mRNA from pre-mRNA and translation is required) LECTURE OUTLINE 1. The Central Dogma of Molecular Biology 2. DNA Replication 2.1 Experimental evidence for the mechanism of DNA replication: The Meselson-Stahl experiment 2.2 Mechanism of semi-conservative DNA replication 2.3 The end-replication problem 3. Gene Expression – Transcription and Translation 3.1 The concept of a gene 3.2 The genetic code 3.3 Gene expression 3.3.1 Transcription 3.3.2 Post-transcriptional modification 3.3.3 Translation 3.3.4 Post-Translational modification 3.4 Summary: Roles of RNAs in protein synthesis 4. Comparisons 4.1 Transcription vs. Translation 4.2 DNA replication vs. Transcription 4.3 DNA replication vs. Translation

4 Biology Unit, Tampines Meridian JC REFERENCES 1) Campbell 9th Edition pages 305-318, 325-343 Web-links And Animations DNA Replication DNA Replication process https://www.youtube.com/watch? v=9EwNHIMfKR8 Meselson-Stahl experiment http://www.sumanasinc.com/ webcontent/animations/content/ meselson.html Transcription Process including binding of transcription factors https://www.youtube.com/watch?v= WsofH466lqk Post-transcriptional modification / RNA processing http://www.youtube.com/watch?v= O0wouZGmXwI Transcription process https://dnalc.cshl.edu/resources/3d/13- transcription-advanced.html Translation: Transcription, RNA splicing, and translation https://dnalc.cshl.edu/view/16933-3D- Animation-of-DNA-to-RNA-to- Protein.html Translation process https://vcell.science/project/translation Translation (prok) showing ribosome sites https://www.youtube.com/watch?v= Ikq9AcBcohA

5 Biology Unit, Tampines Meridian JC Pre-lecture Exercise: How much do you remember about Deoxyribonucleic Acid (DNA)? 1. Nucleic acids are made up of _________________________ (monomers). 2. A nucleotide is made up of a ___________________, a __________________ and a ________________________. 3. DNA nucleotides are called ________________________ while RNA nucleotides are called ______________________. 4. Many free nucleotides join together to form a ___________________ chain via condensation reactions which occur between the 5' ________________ group of one free nucleotide and the ______________ group of the 3' carbon of the previous nucleotide, forming a ______________________ bond. 5. A DNA double helix structure consists of 2 __________________________. 6. The two polynucleotide chains are _________________, i.e. their 5' to 3' orientations run in opposite directions. 7. _____________________