YIJC [H2 BIOLOGY] CI2.6_DNA Mutations

2024 JC1 BIOLOGY LECTURE NOTES CORE IDEA 2: GENETICS AND INHERITANCE TOPIC 2.6: GENE MUTATION Learning Outcomes: (l) Explain what is meant by the terms gene mutation and chromosomal aberration. For gene mutation, knowledge of how substitution, addition and deletion could change the amino acid sequence (including frameshift) is required. (m) Explain how gene mutations can result in diseases (including sickle cell anaemia) Use the knowledge gained in this section in new situations or to solve related problems. References: Reece, J. B. et al. (2018). Campbell Biology (11th Ed). Chapter 17: From Gene to Protein, pp407 – 410. Reece, J. B. et al. (2018). Campbell Biology (11 th Ed). Chapter 15: Linkage and Chromosomes, pp356 – 359. Note: This textbook is available in our library. You may wish to borrow it to supplement your reading when necessary. CONTENTS 1. Introduction 2. Point Mutations 2.1 Base-pair substitution a) Consequence 1: Missense Mutation b) Consequence 2: Nonsense Mutation c) Consequence 3: Silent Mutation 2.2 Base-pair insertion/deletion a) Frameshift Mutation 3. Sickle Cell Anaemia H2

2 1. Introduction Genetic information is stored in linear sequences of base-pairs in DNA. Transcription and translation convert this genetic information into polypeptides, which become functional proteins. Mutations are changes in the nucleotide sequen ce o f DNA or structure/number of the chromosome. This results in an alteration to an organism’s phenotype. Mutation can be spontaneous (e.g. errors during DNA replication resulting in base pair mismatches) or induced by a mutation-causing agent (e.g. Ethidium Bromide) DNA mutations can have numerous biological implications  Disease causing (e.g. mutations to proto-oncogenes contribute to onset of cancer)  Creation of new gene variants, which contributes to diversity of genes and allows natural selection and evolution to take place There are two main types of mutation: gene mutation and chromosomal aberration. 1. 2. 3. Transcription Translation 4. Determine phenotype (Observable traits, e.g. hair colour) Recall the Central Dogma of Molecular Biology What is the significance of a change in DNA structure and sequence? DNA mutations Chromosomal Aberrations Numerical Aberrations Structural Aberrations Change in number of chromosomes Change in structure of chromosomes Gene mutations Involves chemical changes in linear DNA sequence Change in DNA nucleotide sequence More will be elaborated on in Topic 2.7 Focus of this topic (Topic 2.6)

3 What is the relationship between gene mutation and protein synthesis process? Mutation in DNA resulting in change in …………………………… Change in …………………………….. Change in …………………………….. Affect ……………… of polypeptide into specific …………………………….. Ch