13: How Alleles Arise - Mutations — Read

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13.0: Introduction
This page covers the origins and impacts of genomic DNA mutations, explaining their transformation into alleles in populations. It differentiates between heritable germ line mutations and non-heritable somatic mutations, noting their causes such as replication errors and environmental damage.
13.1: Mutations into alleles
This page discusses how mutations can become alleles in a population, emphasizing that they must avoid early lethal effects to be passed on. In diploids, dominant mutations can express phenotypes, but new mutations struggle with issues such as meiosis loss and genetic drift. For recognition as an allele, a mutation must exceed 1% prevalence in the population.
13.2: Luria and Delbrück- Discovering the origin of mutations
This page examines early misconceptions in evolutionary theory, contrasting Darwinian randomness with Lamarckian purpose. It highlights the crucial Luria-Delbrück experiment that showed bacterial resistance mutations occur spontaneously, supporting the Darwinian model and demonstrating mutation rate variability across cultures.
13.3: Forward and reverse genetics
This page covers forward genetics, a technique for identifying mutations that impact specific traits through random mutation generation, using Drosophila melanogaster as a model organism. It highlights the ability to study traits like eye shape or color while noting the challenges in genetic analysis, as some mutations may be missed if they involve essential survival genes, which renders forward genetic screens incomplete in capturing all genes associated with a phenotype.
13.4: Generating specific mutations on demand - CRISPR-Cas9 and related technologies
This page discusses the evolution of genetic research methods, highlighting the shift from traditional forward genetics to modern techniques like CRISPR-Cas9. Developed by Charpentier and Doudna, CRISPR-Cas9 allows for precise DNA editing through target-specific RNA guidance and is capable of inducing double-stranded breaks, resulting in mutations.
13.5: Longer term mutation and evolution studies
This page discusses the spontaneous mutation model, highlighting that mutations occur randomly and can evolve into alleles. It reviews Richard Lenski's E. coli study, which showed how beneficial mutations arise from pre-existing mutations, reflecting natural selection. Additionally, a study on bacterial evolution and antibiotic resistance emphasizes the role of clonal reproduction in mutation and selection.

This page titled 13: How Alleles Arise - Mutations was last modified on Thu, 08 Jan 2026 22:57:28 GMT and is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Michael W. Klymkowsky and Melanie M. Cooper.

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