Population Genetics

• Population Genetics: The study of genetic variation within populations, focusing on changes in genetic composition over time.

• Relevance:

  • Inheritance Patterns: Helps in understanding how traits pass from one generation to the next.
  • Genetic Diversity: Essential for a population's ability to adapt and survive.
  • Evolutionary Processes: Key to explaining adaptation and evolutionary changes.

Key Principles of Population Genetics

Genetic Variation

• Genetic Variation: Differences in genetic traits within a population.

• Sources and Examples:

  • Mutations: Random alterations in DNA sequences, such as mutations that change the colour of flower petals.
  • Gene Flow: Exchange of genes, for example, through pollen transfer, introducing new traits.
  • Genetic Drift:
    • Random changes in allele frequencies, particularly significant in small populations.
    • Example: Natural disasters may alter allele frequencies by random chance.
  • Natural Selection:
    • Traits that are advantageous become more prevalent.
    • Example: Moths that match their environment are less likely to be preyed upon, increasing their survival.

Hardy-Weinberg Principle

• Assumptions:

  • No mutations.
  • Large population size.
  • Random mating.
  • No migration.
  • No selection.

• Equation and Example: $p^2 + 2pq + q^2 = 1$

  • Example: In rabbits, where 1 in 10,000 shows a recessive white fur trait:
    • Step 1: Let $q^2 = \frac{1}{10000}$, so $q = 0.01$.
    • Step 2: Frequency of the dominant allele: $p = 0.99$.
    • Conclusion: Dominant alleles are common, suggesting the recessive trait remains rare, indicating genetic stability.

Diagram: Allele Frequencies

• Caption: Stability of allele frequencies under ideal conditions.

Reproduction and Species Continuity

Overview

• Reproduction: Essential for species continuity, critical for survival and adaptation.
  • Promotes genetic diversity.
  • Essential Processes: Meiosis and Fertilisation.

Biological Processes

• Meiosis and Gamete Formation:

  • Meiosis: Creates genetically diverse gametes.
  • Processes:
    • Interphase: DNA replication occurs.
    • Prophase: Chromosomes condense and crossing over occurs.
    • Metaphase: Chromosomes align.
    • Anaphase: Chromosomes move towards poles.
    • Telophase: Nuclear membranes reform.
    • Cytokinesis: Cell division completes.
  • Crossing Over: Exchange of genetic material.
  • Independent Assortment: Random segregation of chromosomes.

• Genetic Diversity:

  • Random Fertilisation: Combines diverse gametes, increasing variability.
  • Mutations: Spontaneously introduces new traits.

Visuals

• 

  • Flowchart: Crossing Over and Independent Assortment.

• 

  • Diagram: Comparison of sexual and asexual reproduction impacts.

Mechanisms of DNA Replication

• DNA Replication Process:

  • DNA helicase: Opens the DNA double helix.
  • DNA polymerase: Adds nucleotides forming a new strand.
  • Ligase: Seals any gaps.

• Semi-conservative Nature: Each new DNA molecule retains one original strand.

• Replication Fork:

  • Leading Strand: Synthesised continuously.
  • Lagging Strand: Synthesised in fragments.

Error-Checking

• Proofreading by DNA polymerase:
  • Corrects errors, acting as a quality control.
• Mismatch Repair:
  • Functions similarly to a spellchecker, correcting errors after synthesis.

Errors Consequences

• Mutations:
  • Can result in genetic disorders like Cystic Fibrosis and Sickle Cell Anaemia.
  • Types of Errors:
    • Point Mutations: Changes in a single base pair.
    • Insertions/Deletions: Larger changes that can lead to disorders.

Transcription and Translation

Transcription

• Process: Conversion of DNA into mRNA.
  • RNA polymerase: Facilitates the addition of RNA nucleotides.
  • Stages:
    • Initiation: Enzyme attachment.
    • Elongation: Formation of the RNA strand.
    • Termination: End of the sequence is reached.

Translation

• Decoding mRNA into proteins:
  • mRNA: Provides the sequence.
  • tRNA: Delivers amino acids.
  • Ribosomes: Assemble the polypeptide chain.

Introduction to Genetic Comparisons

• Genetic Comparisons: Reveal evolutionary relationships, species divergence, and trait development.

Methods for Genetic Comparisons

• DNA Sequencing:

  • NGS: A rapid technique for complete genome analysis.

• Molecular Markers:

  • SSRs and SNPs: Identify genetic characteristics and variations.

Phylogenetic Analysis

• Phylogenetic Trees: Illustrate evolutionary connections.

Visual Aid

Predicting Genetic Patterns

Methods for Prediction

• Computer Modelling:

  • Stochastic and Deterministic Models: Predict genetic trends and outcomes.

• Statistical Methods:

  • Regression Analysis, Probability Distribution: Enhance precision in predictions.

Large-Scale Data Projects

• Human Genome Project (HGP): Comprehensive genome mapping effort.

• International HapMap Project: Catalogued genetic variations.

• 1000 Genomes Project: Expanded genetic datasets.

Ethical Considerations

• Concern: Ensuring privacy and security in managing genetic data.

Visuals

Conclusion

• Population genetics supports evolutionary theories and conservation efforts by forecasting patterns, deepening our understanding of genetic trends, and aiding biodiversity management.