RVHS 8. Transcription and Translation 9477

River Valley High School 1 2025 JC1 H2 Biology Lecture Topic 8: Transcription and Translation River Valley High School 2025 JC1 H2 Biology Lecture Topic 8: The Structure of Nucleic Acids and Gene Expression – Transcription and Translation Name: ( ) Class: 25J___ Date: References Title Author Biology (9th edition) Campbell and Reece Molecular Biology of the Cell (5th edition) Alberts, Johnson, Lewis, Raff, Roberts and Walter Biological Science 1 and 2 (3rd Edition) Taylor, Green and Stout Molecular Biology of the Cell (5th edition) Alberts, Johnson, Lewis, Raff, Roberts and Walter Principles of Genetics (3rd edition) Snustad and Simmons Molecular Cell Biology (6th edition) Lodish, Berk, Kaiser, Krieger, Scott, Bretscher, Ploegh and Matsudaira Advanced Biology: Principles and Applications (2nd edition) Clegg and Mackean Websites URL Description http://learn.genetics.utah.edu/content/basics/transcribe/ Interactive website on protein synthesis https://highered.mheducation.com/sites/9834092339/stu dent_view0/chapter15/protein_synthesis.html Watch the video linked on page 10 and complete the Chapter 15 quiz to reinforce your understanding of the concepts. http://www.dnaftb.org/ Plenty of animations / video clips for DNA- related mechanisms. Refer mainly to “Molecules of Genetics” tab

River Valley High School 2 2025 JC1 H2 Biology Lecture Topic 8: Transcription and Translation H2 Biology Syllabus 9477 (2025) Candidates should be able to use the knowledge gained in the following section(s) in new situations or to solve related problems. Related Topics Content DNA Replication DNA structure and function Learning Outcomes 2A. The Structure of Nucleic Acids and Gene Expression a. describe the structure and roles of DNA and RNA (tRNA, rRNA and mRNA) c. Describe how the information on DNA is used to synthesise polypeptides (description of the processes of transcription, formation of mRNA from pre -mRNA in eukaryotes and translation is required) Lecture Outline I. Central Dogma of Molecular Biology II. Transcription (Synthesis of RNA) A. Structure of RNA B. Overview of Transcription C. Process of Transcription D. Features of mRNA III. Translation (Synthesis of Polypeptides) A. Overview of Translation B. Features of the Genetic code C. Structure-Function Relationships of tRNA D. Structure-Function Relationships of ribosome E. Process of Translation F. From Polypeptide to Functional Protein

River Valley High School 3 2025 JC1 H2 Biology Lecture Topic 8: Transcription and Translation I. Central Dogma of Molecular Biology ⬧ Central dogma of molecular biology – the flow of genetic information in all cells, from DNA to DNA and from DNA to RNA to protein. ⬧ Genetic information is transferred from DNA to DNA during its transmission from generation to generation. ⬧ Genetic information is transferred from DNA to RNA and then to protein during its phenotypic expression in an organism. o Information flow is unidirectional. o All RNAs are transcribed from DNA by transcription. The base sequence of DNA is ‘copied’ into the messenger molecule (messenger RNA). Location: nucleus (eukaryotes only) o All proteins are ‘copied’ from mRNA by translation. Three consecutive mRNA nucleotide bases specify one amino acid in a polypeptide chain using a genetic code that is the same for all organisms. Location: cytoplasm ⬧ Key difference in the flow of genetic information between bacteria and eukaryotes:

River Valley High School 4 2025 JC1 H2 Biology Lecture Topic 8: Transcription and Translation o In bacteria, the absence of a nuclear membrane allows DNA to share the same space as the protein synthesi sing machinery in cytoplasm. ➢ This allows translation of mRNA to begin while transcription is in progress. o In eukaryotes, the presence of a nuclear membrane separates DNA in the nucleus from the protein synthesising machinery in the cytoplasm. ➢ This causes transcription and translation to take place in different space and at different time. ➢ The initial RNA transcripts (pre-mRNA) are processed in the nucleus before they are permitted to exit the nucleus as mRNA and be translated into a polypeptide. II. Transcription (Synthesis of RNA) Definition: synthesis of a RNA molecule with a base sequence complementary to a section of DNA , i.e. a gene. A gene can be defined as: a. a segment of DNA with a unique nucleotide/base sequence that encodes information specifying the construction of a particular RNA molecule / polypeptide chain. b. a unit of inheritance specifying a particular biological function – phenotype. This unit of inheritance is located in a fixed position (called locus) on the chromosome. (KIV: Inheritance) Figure showing transcription and translation occurring simultaneously in bacterial cytoplasm

River Valley High School 5 2025 JC1 H2 Biology Lecture Topic 8: Transcription and Translation A. Structure of RNA – Intermediaries between DNA and Polypeptide ⬧ Similarities between RNA and DNA: 1. Presence of phosphoester bonds between monomers 2. Four different types of nitrogenous bases ⬧ Differences between RNA and DNA: Parameter RNA DNA Molecular mass Smaller (20 000 to 2 000 000) Larger (100 000 to 150 000 000) Primary structure 1 polynucleotide strand 2 polynucleotide strands Shape Variable shapes such as the L-shaped structure of tRNA Almost always a double helical molecule Purine / Pyrimidine ratio A/U ≠ G/C ≠ 1 A/T = G/C = 1 Location Synthesised in nucleus but found throughout the cell (eukaryotes) Found almost entirely in the nucleus and in mitochondria and chloroplasts (eukaryotes) Pentose sugar Ribose Deoxyribose Chemical stability Less stable – ribose has an additional reactive 2’OH group More stable – deoxyribose lacks 2’OH group Nitrogenous bases Adenine, Guanine, Cytosine, Uracil Adenine, Guanine, Cytosine, Thymine Basic forms Several different kinds and sizes, each with its own function: 1. Messenger RNA (mRNA) 2. Transfer RNA (tRNA) 3. Ribosomal RNA (rRNA) 4. Small nuclear RNA (snRNA) Only one basic form, but with an almost infinite variety within that form Amount per cell Varies from cell to cell (and within a cell according to metabolic activity) Constant for all cells of a species (except gametes and spores)

River Valley High School 6 2025 JC1 H2 Biology Lecture Topic 8: Transcription and Translation ⬧ Analysis of the RNA content of cells has shown the existence of three basic types of RNA, all of which are involved in protein synthesis. These are messenger RNA, transfer RNA and ribosomal RNA. All three types are synthesised directly from DNA, which is said to act as template for RNA production, and the amount of RNA in each cell is directly related to the amount of protein synthesis. Type of RNA Structure Function(s) Messenger RNA (mRNA) ⬧ Short, linear, single-stranded RNA corresponding to a gene encoded within DNA. ⬧ Has a 5’ modified guanine nucleotide and a 3’ poly-A-tail. ⬧ Is unstable and degraded easily. Carries information specifying the amino acid s equences of proteins from DNA. Serves as the template in translation by ribosomes Transfer RNA (tRNA) ⬧ Short (70-90 nucleotides), stable RNA with extensive hydrogen bonds with complementary bases (A-U, C -G) to acquire a cloverleaf shape (2D). ⬧ Comprises of 3 loops – anticodon loop (binds to mRNA codon), D -loop (activating enzyme site) and T -loop (ribosome recognition site) ⬧ And a 3’ CCA stem - an amino acid binding site Carries specific amino acids to mRNA on ribosome for protein synthesis. Ribosomal RNA (rRNA) ⬧ Longer, stable RNA molecules composing 60% of ribosome’s mass. ⬧ Has varied 3D conformations. Plays structural and enzymatic roles in ribosomes –