Mutações Gênicas - Aula 20 - Módulo II: Genética | Prof. Gui

Introduction to Mutations

The instructor introduces the concept of mutations, focusing on genetic changes and their significance in biology exams like Enem.

Understanding Mutations

• A mutation is any genetic alteration, such as gaining or losing a nitrogen base in DNA, resulting in genetic changes.

• Mutations occur randomly and are typically avoided by organisms through mechanisms that correct or eliminate mutated cells to prevent disorders like cancer.

• Mutations are not intentional; organisms do not purposefully induce mutations. For example, the elongated neck of a giraffe was not intentionally developed through mutations.

• Antibiotics act as selective factors rather than causing mutations. They select for resistant bacteria due to random mutations, contributing to genetic variability.

Role of Mutations in Evolution

Discusses how mutations contribute to genetic variability within populations and their role in evolutionary theory.

Evolutionary Significance

• Mutations are crucial for genetic variability within populations, a concept initially lacking explanation in Darwin's theory but later understood through genetics.

Understanding Mutations and Their Impacts

In this section, the speaker discusses mutations caused by solar radiation and their implications on heredity. The classification of mutations as neutral, deleterious, or favorable is also explored.

Types of Mutations

• Neutrality of Mutations:

• Neutral mutations do not impact an organism's survival or evolutionary aspects.

• Example: A mutation changing eye color without affecting survival.

• Deleterious vs. Favorable Mutations:

• Deleterious mutations cause harm without providing benefits.

• Favorable mutations offer advantages like increased resistance or reproductive success.

• Context-dependent: Blindness may be neutral for bats but detrimental for diurnal species.

Gene Mutations

• Gene Mutation Definition:

• Alters DNA base sequences affecting nucleotides in genetic material.

• Bases (adenine, thymine, cytosine, guanine) form nucleotides influencing genetic traits.

• Types of Gene Mutations:

• Insertion: Addition of bases during DNA replication leading to altered protein formation.

• Deletion: Loss of bases causing reading frame shifts and incorrect protein synthesis.

Impactful Substitutions

• Substitution Effects:

• Substitutions replace one base with another, potentially altering amino acids in proteins.

Silent Substitution and Sickle Cell Anemia

In this section, the speaker discusses silent substitutions in genetic coding and transitions to explaining sickle cell anemia as a result of a specific genetic mutation.

Silent Substitutions in Genetic Coding

• The genetic code can be degenerate, where different codons can code for the same amino acid.

• Silent substitutions occur when a mutation does not affect protein production, known as synonymous mutations.

• Ribosomes read DNA sequences in groups of three to produce proteins; stop codons signal the end of protein synthesis.

• Nonsense mutations lead to premature stop codons, affecting protein production.

Sickle Cell Anemia Mutation

• Sickle cell anemia results from a specific genetic substitution causing a change in hemoglobin structure.

• A single nucleotide change from GAG to GTG leads to valine instead of glutamic acid in hemoglobin.