BIO MICROEVOLUTION Revision session

Course Information

• Course Code: BIOEB201-23A

• Title: Principles of Evolution

• Instructor: Dr. Ang

Revision Session

Focus: Microevolution

• Key topics related to microevolution will be reviewed in this session to enhance understanding of evolutionary processes over small timescales.

Session Format

• Google Document Access: Participants are encouraged to access a shared Google Document during the session.

• Volunteer Participation: Students are invited to add notes and contribute during the session to foster collaborative learning.

Questions and Key Concepts

Difference Between Polymorphism and Single Nucleotide Polymorphism (SNP)

• Polymorphism: Refers to the occurrence of two or more variants (alleles) at a locus within a population.

• Single Nucleotide Polymorphism (SNP): A specific type of polymorphism, where only a single nucleotide differs between individuals.

• Understanding these distinctions is crucial in genetics and evolutionary biology.

Sources of Variation

• Mutation: A fundamental source of genetic variation.

• Gene Flow: The transfer of alleles or genes from one population to another, increasing genetic diversity.

• Sexual Reproduction: Introduces new combinations of genes, contributing to variation.

Nucleotide Diversity

Definition and Importance

• Nucleotide Diversity: A measure of genetic variation at the level of nucleotide sequences within a population.

• Conservation Implications: Higher nucleotide diversity is generally preferred in endangered species as it contributes to adaptive potential and resilience against environmental changes.

Dominant and Recessive Alleles

• Dominant Alleles: Traits expressed in the presence of one or two copies (e.g., AA or Aa results in tall phenotype).

• Recessive Alleles: Traits expressed only when two recessive alleles are present (aa), often linked to reduced protein expression, which can affect phenotype.

Negative/Purifying Selection

• Definition: A form of natural selection that removes deleterious alleles from a population, often enhancing the overall fitness of the population.

• Example: Individuals carrying harmful alleles tend to have lower reproductive success, leading to a decrease in those alleles in future generations.

Underdominance Selection vs. Random Genetic Drift

• Underdominance Selection: Occurs when heterozygotes have lower fitness compared to both homozygotes, which can lead to allele fixation or loss.

• Comparison with Genetic Drift: Genetic drift refers to random changes in allele frequencies, which can also affect fitness but without directional selection pressure.

Synonymous Mutations and Phenotypic Change

• Synonymous Mutations: Refers to mutations that do not change the amino acid sequence of the resultant protein.

• Phenotypic Effects: While typically not altering protein functions, they may influence gene expression, folding, and other factors that can impact phenotypic traits—illustrated by the example of structural changes in digits (e.g., resulting in 6 fingers).

• Nonsynonymous Mutations: These mutations change the amino acid sequence, potentially resulting in loss of function or gain of new functions, as seen in codon substitutions.

Upcoming Quiz

• Details:

  • Start Date: Wednesday, 12 PM, 5th April

  • End Date: Sunday, 11:30 PM, 9th April

Evolutionary Outcomes in Isolated Populations

Case Study: Panthers

• Scenario: A population of panthers is split into isolated northern and southern groups.

• Immediate Effects: Potential decline in genetic diversity due to reduced gene flow and increase in genetic drift, especially in the southern population facing resource challenges.

• Long-term Predictions:

  • FST Changes: Expect an increase in fixation index (FST) due to the drift that separates the populations over time.

  • Diversity Effects: Diversity within each population is expected to decrease, particularly in the southern population that is struggling to survive.

Exam Strategies

• Reading Questions: Emphasizes the importance of carefully interpreting exam questions to ensure all parts are answered adequately.

• Marks as Guidelines: Use the mark distribution to time management and point allocation in responses for structured answers.