19.Mutagenic factors and mechanisms of DNA changing.
Covers what gene mutations are and how they are classed: somatic versus germ line, harmful, beneficial or neutral, substitution, insertion or deletion, and spontaneous versus induced. It then explains the mechanisms behind substitutions (transitions, including tautomerization and deamination, and transversions), insertions and deletions (AP sites, slipped-strand mispairing with a Huntington's example, intercalating agents), and external mutagens such as UV light, base analogues, nitrous acid and nutrient deficiency. The note closes with how different mutation types alter protein structure, including silent, missense, nonsense, frameshift, splice-site and regulatory changes.
Topic 19 of 63 in the MU Pleven syllabus for Biology (Medicine, Year 1). The free AceMed note covers it in 11 sections, about 595 words (4 min of reading), with 11 flashcards.
Effects of Gene Mutations on Protein Structure and Function
A. Substitution Effects
B. Insertions and Deletions
C. Mutations Outside Coding Regions
Gene Mutations
1. What Are Gene Mutations?
Gene mutations are changes in the DNA sequence that occur without the cell's intentional control.
These changes typically involve small-scale alterations in one or a few nucleotides.
Mutations play a crucial role in evolution as they create new genetic variants, which natural selection can act upon.
Many mutations appear after the cell attempts to repair chemical injuries to the DNA. While the DNA may survive the repair with a changed sequence, it cannot survive the initial damage itself.
Classification of Gene Mutations
A. Based on the Cell Type Affected and Inheritance
Somatic mutations occur in body cells and are not passed on to offspring unless reproduction is asexual.
Germ line mutations occur in reproductive cells and can be inherited by the next generation.
Based on Impact on an Organism’s Fitness
Harmful mutations reduce an organism’s chances of survival or reproduction.
Beneficial mutations improve fitness and offer a survival advantage.
Neutral mutations do not affect fitness but may still be passed on. They form the basis of the molecular clock due to their steady rate of occurrence.
Whether a mutation is harmful or beneficial may depend on environmental conditions.
Based on the Structural Change in DNA
Substitution: Replacement of one nucleotide with another.
Insertion: Addition of one or more nucleotides.
Deletion: Removal of one or more nucleotides.
Based on the Cause of Mutation
Spontaneous mutations: Occur naturally due to internal factors.
Induced mutations: Caused by external agents called mutagens.
Continue reading free
The whole note, all 11 sections, is free with an AceMed account, with its 11 flashcards. Premium adds flashcard recall, highlights and Ask AI.
