Microevolution Notes

Flu Vaccines

  • Selection of three flu virus strains is conducted in January.

  • Vaccine production, packaging, and shipping occur from July through October.

  • Vaccination typically takes place from November to January.

  • Importance of annual vaccine updates:

    • New flu vaccine is necessary each year due to mutation of the virus.

Antivirals Development

  • Reason for developing new antivirals:

    • The Hepatitis B virus (HBV) can develop resistance to existing antivirals.

    • Timeline event:

    • Initiation of antiviral therapy leads to the development of a mutant virus capable of more effective replication.

    • Virologic breakthrough occurs when resistant strains emerge.

    • Discontinuation of antiviral agents can lead to the re-emergence of wild-type viruses.

  • Source: Medscape.

Antibiotics Development

  • Necessity of developing new antibiotics:

    • Due to mutation and natural selection among bacterial populations, resistance is increasingly common.

Understanding Mutation

  • Definition of Mutation:

    • A mutation is defined as a change in the nucleotide sequence of a nucleic acid (DNA or RNA).

    • This includes the alteration, removal, or addition of one or more nucleotides (A, T, C, G in DNA; A, U, C, G in RNA).

DNA and Protein Synthesis

  • Definition of DNA:

    • DNA is a nucleic acid composed of nucleotides that carry the genetic instructions for building proteins.

  • Effects of DNA changes on RNA:

    • Any change in the DNA sequence (e.g., AAGTGCGT → UUCACGCA in RNA) leads to a change in the corresponding RNA sequence during transcription.

  • If the mRNA sequence is altered, the resultant amino acid sequence may also change, potentially impacting protein functionality.

Amino Acids and Protein Structure

  • The primary structure of a protein is determined by the amino acid sequence:

    • This structure determines secondary, tertiary, and quaternary protein configurations which directly influence function.

Types of Mutations

  • Point Mutations:

    • Silent: No effect on protein sequence.

    • Missense: Results in an amino acid substitution, affecting protein function.

    • Nonsense: Results in a premature stop codon, truncating the protein.

    • Frameshift Mutations: Involves insertions or deletions disrupting the reading frame, potentially introducing stop codons prematurely.

Implications of Mutations

  • Mutations create new versions of genes, and not all mutations yield negative consequences:

    • Some mutations are silent, some beneficial, and others harmful.

  • Example of a beneficial mutation: Sickle Cell Anemia

    • Normal DNA sequence (GAG) may change to (GTG), leading to abnormal hemoglobin.

    • Individuals with the sickle cell gene are resistant to malaria.

Sickle Cell Disease Facts

  • Inheritance patterns:

    • Sickle cell disease (SCD) occurs in individuals who inherit two sickle cell genes, one from each parent.

    • Individuals with one sickle cell gene have sickle cell trait (SCT).

  • Prevalence and common regions:

    • SCD is particularly prevalent among individuals with African ancestry.

  • Treatment options: Bone marrow transplants can cure SCD for some patients but carry risks.

  • Living with SCD:

    • Regular medical check-ups and healthy habits enhance quality of life and longevity for patients with SCD.

Characterization of Evolution

  • Definition of Evolution in biology:

    • Common descent with modification refers to changes in traits and frequencies due to mutation and natural selection.

  • Understanding “fitness” in evolution:

    • Fitness refers to the transmission of genes to subsequent generations, often indicated by the number of offspring.

    • Survival alone isn’t enough; reproductive success is key.

Fitness Example Analysis

  • Evaluating fitness among organisms:

    • Organism A: 5 offspring, 100 years.

    • Organism B: 6 offspring, 80 years.

    • Organism C: 10 offspring, 50 years.

    • Organism D: 1 offspring, 30 years.

    • Highest fitness: Organism C (10 offspring) despite shortest lifespan.

Key Principles of Natural Selection

  • For natural selection to occur:

    • Traits must be heritable

    • Variation in traits must exist within the population

    • Selective pressures must favor some traits over others

    • Example: antibiotic resistance illustrates natural selection principles directly.

Microevolution

  • Definition of microevolution:

    • Changes in allele frequencies in populations over generations.

  • Key agents of microevolution include:

    1. Mutations which introduce new alleles.

    2. Gene flow from migration altering allele distributions.

    3. Genetic Drift, primarily affecting small populations and creating random fluctuations in allele frequencies.

    4. Natural Selection acting based on the adaptive advantages of traits.

Further Exploration of Genetic Drift

  • Genetic drift impacts population dynamics:

    • More pronounced in smaller populations.

    • Example: a rare allele is more likely to be lost in small populations than in large ones.

Summary of Key Concepts

  • Natural selection leads to evolution through the survival and reproduction of organisms better adapted to their environment, while mutations, gene flow, and genetic drift contribute to genetic variability within populations.