Gregor Mendel

Gregor Mendel and Genetics

  • Known as the "Father of Genetics"; biologist, mathematician, and meteorologist.

  • Born July 20, 1822; studied at University of Vienna.

  • Conducted pea plant experiments from 1856 to 1863 to study heredity.

Key Concepts of Genetics

  • Genetics: Study of heredity; how traits are passed from parents to offspring.

  • Heredity: Passing of physical characteristics (traits) genetically.

  • Genes: Basic units of heredity made of DNA, organized on chromosomes in cell nuclei.

Mendel's Pea Plant Experiment

  • Initial Observation: Crossed purple and white flowered pea plants; all offspring were purple.

  • Noted segregation of traits in self-pollinated offspring: some purple and some white flowers.

Pea Plant Traits

  • Key characters observed by Mendel: height, flower position, pod color, seed texture, seed color, and flower color.

  • Traits are specific forms of characters (e.g., purple or white flowers).

Flower Anatomy and Types

  • Complete Flower: Both male (staminate) and female (pistillate) parts present.

  • Imperfect Flowers: Single sex organs; examples include corn and cucumber (monoecious) vs. papaya (dioecious).

Pollination Techniques

  • Manual transfer of pollen from anther to stigma; includes self-pollination and cross-pollination.

Experimental Design

  • True-breeding plants (P1 generation) were used; their hybrids (F1) self-pollinated to produce F2 generation.

  • Dominant (expressed) and recessive (not expressed when dominant is present) alleles were identified.

Key Terminology

  • Genotype: Genetic makeup; e.g., Pp for a purple flowered plant.

  • Phenotype: Physical traits; e.g., purple flower color.

  • Homozygous & Heterozygous: Homozygous has identical alleles (PP or pp), heterozygous has different alleles (Pp).

Punnett Squares and Inheritance Patterns

  • Punnett squares used to predict genetic crosses.

  • Types of dominance: Incomplete dominance, codominance, and multiple alleles are important concepts in inheritance patterns.

  • Example: Incomplete dominance occurs in snapdragons (Rr yields pink flowers).