Lecture_3.1: intro to genetics

Introduction to Genetics

  • Basic genetic knowledge is essential for understanding evolution.

  • Evolution is defined as genetic change over time; it necessitates biological variation within species.

Biological Variation

  • Natural populations exhibit variability in traits; laboratory clones may lack variation.

  • No evolutionary change can occur without variation in a characteristic.

  • Focus on animals that reproduce sexually, as reproduction transmits biological variations.

Historical Context

  • Prior to Mendel's work (rediscovered in 1900), the particulate nature of inheritance was unknown.

  • Darwin proposed natural selection independent of how characteristics were inherited.

  • Genetic advancements in the 1930s to 1950s enhanced the credibility of evolutionary theories.

Levels of Genetic Analysis

  • Molecular Level: Concerns individual DNA and genes.

  • Chromosomal Level: Involves groups of genes on chromosomes; structure central to inheritance.

  • Population Level: Focus on evolutionary forces and gene frequency changes; foundational for evolutionary study.

    • Molecular and chromosomal basics needed for understanding population genetics.

Chromosomes and Heredity

  • Chromosome Definition: Structures in cell nuclei, identified by early 20th-century researchers.

  • Humans have 46 chromosomes arranged in 23 pairs (22 autosomes and 1 pair of sex chromosomes).

  • Chimpanzees have 48 chromosomes, indicating chromosomal fusions in human evolution.

  • Autosomes are homologous, while sex chromosomes differ in structure (XX for female, XY for male).

Definitions of Genes

  • A gene can be defined as:

    • A portion of DNA with a detectable function (unit of heredity).

    • A unit of DNA that produces a functioning protein.

    • Importance of proteins:

      • Enzymes catalyze reactions.

      • Proteins transport substances (e.g., oxygen, hormones).

      • Structural proteins (e.g., collagen) provide support.

      • Antibodies fight infections and proteins regulate gene expression.

Protein Synthesis and DNA

  • DNA consists of a sugar-phosphate backbone and four nitrogenous bases (A, T, C, G).

  • DNA is self-replicating, and its structure is a double helix.

  • During replication, the double helix unwinds, allowing complementary bases to pair.

  • Final result: Two identical DNA molecules, each with one old and one new strand.

  • The process of linking amino acids to build proteins is protein synthesis.