Lecture on Genes and Evolution

Introduction

• Darwin's Observations: Variation in natural populations.
  • Traits inherited by offspring.
  • Mechanism unknown to Darwin.

Discovery of Genes

• Gregor Mendel: Discovered genes in the 1850s.
  • Austrian monk and high school teacher.
  • Experimented with pea plants (1856-1863).
  • Published results in 1866.
  • Became Abbot in 1887, ceased biological research.

Mendel's Experiments

• Traits Studied:
  • Stem length: Short or long/viny.
  • Flower distribution: Throughout or just at top.
  • Pod color (unripe): Yellow or green.
  • Pod shape: Inflated or pinched.
  • Flower color: Purple or white.
  • Seed interior: Yellow or green.
  • Seed shape: Round or wrinkled.
• Inheritance Systems:
  • Contributions from two parents.
  • Traits have dominant and recessive versions.
    • Dominant: Expressed if present.
    • Recessive: Expressed only if two copies are present.
  • Notation: Uppercase for dominant, lowercase for recessive.

Genetic Vocabulary

• Homozygous:
  • Two same copies of a gene.
  • Homozygous dominant (AA) or recessive (aa).
• Heterozygous:
  • Different copies of a gene (Aa).

Mendel's Ratios and Predictions

• Genetic Crosses:
  • Heterozygous cross: Aa x Aa.
  • 1/4 homozygous dominant, 1/4 homozygous recessive, 1/2 heterozygous.
  • Phenotypic expression: 3/4 dominant, 1/4 recessive.

Mendel's Contributions and Limitations

• Demonstrated binary system of inheritance.
• Traits can be dominant or recessive.
• Predict inheritance ratios.
• Controversy: Cooked data, statistical understanding limited.

Genes and Evolution

• Genotype: Genes an organism possesses.
• Phenotype: Expression of genotype.
• Sources of Variation:
  • Sexual reproduction: Recombines genes.
  • Genetic mutation: Rare beneficial mutations can create new species.
• Example: Cope's gray tree frog and gray tree frog species discovery.

Key Points on Evolution

• Darwin's Natural Selection:
  • Different traits affect reproduction.
  • Traits must be heritable.
• Mendel's Importance:
  • Discovery of genes.
  • Unrecognized in his time.

Natural Selection Beyond Biology

• Cultural Entities: Businesses, economic systems.
  • Requires variability, heritability, reproduction influence.

Types of Genes

• Structural Genes:
  • Code for proteins and enzymes.
  • Drive evolutionary change at a small scale.
• Regulatory/Informational Genes (Hox genes):
  • Control development, specify body regions.
  • Similar across vertebrates and arthropods.

Hox Genes and Evolutionary Change

• Complexity:
  • More Hox gene copies in vertebrates.
  • Example: Mutation in flies changing antenna to legs.

Skeletal Structures in Mammals and Dinosaurs

• Mammals:
  • Stereotypical skeletons (206 bones, 7 cervical vertebrae).
• Dinosaurs:
  • Flexible skeletal configuration (e.g., sauropods).
  • Hox genes in dinosaurs may allow more mutation and change.