LECTURE CONNECTIONS 3 | Basic Principles of Heredity © 2009 W. H. Freeman and Company

Chapter 3 Outline 3.1 Gregor Mendel Discovered the Basic Principles of Heredity, Monohybrid Crosses Reveal the Principle of Segregation and the Concept of Dominance, Dihybrid Crosses Reveal the Principle of Independent Assortment, Observed Ratios of Progeny May Deviate from Expected Ratios by Chance, 62

3.1 Gregor Mendel Discovered the Basic Principles of Heredity Gregor Mendel and his success in genetics Genetic Terminology

What Monohybrid Crosses Reveal Predicting the Outcomes of Genetic Crosses The Testcross Incomplete Dominance Genetic Symbols 3.2 Monohybrid Crosses Reveal the Principle of Segregation and the Concept of Dominance

Conclusion 1: One character is encoded by two genetic factors. Conclusion 2: Two genetic factors (alleles) separate when gametes are formed. Conclusion 3: The concept of dominant and recessive traits. Conclusion 4: Two alleles separate with equal probability into the gametes. Monohybrid cross: cross between two parents that differ in a single characteristic

3.2 Monohybrid Crosses Reveal the Principle of Segregation and the Concept of Dominance Principle of segregation: (Mendel’s first law) Each individual diploid organism possesses two alleles for any particular characteristic. These two alleles segregate when gametes are formed, and one allele goes into each gamete. The concept of dominance: When two different alleles are present in a genotype, only the trait encoded by one of them – the “dominant” allele – is observed in the phenotype.

3.2 Monohybrid Crosses Reveal the Principle of Segregation and the Concept of Dominance Relating Genetic Crosses to Meiosis Chromosome theory of heredity

3.2 Monohybrid Crosses Reveal the Principle of Segregation and the Concept of Dominance Predicting the outcomes of genetics crosses The Punnett square

3.2 Monohybrid Crosses Reveal the Principle of Segregation and the Concept of Dominance The Testcross Incomplete Dominance Ratios in Simple Crosses

3.3 Dihybrid Crosses Reveal the Principle of Independent Assortment Dyhybrid Crosses The Principle of Independent Assortment Relating the Principle of Independent Assortment to Meiosis Applying Probability and the Branch Diagram to Dihybrid Crosses Dihybrid Testcross