Inheritance and Genetics

1. Inheritance and Genetics

2. Gregor Mendel • Studied the garden pea • studied height, flower color, seed coat color, and seed shape over many generations • he chose 1 or 2 traits per generation to watch • crossed plants with different traits and learned that offspring usually had dominate trait

3. Discovery • Mendel found that the inheritance of traits was not due to blending but instead specific traits or units of inheritance were passed from generation to generation • we call those units of inheritance genes

4. No matter what trait he selected for the second generation would show traits at a ratio of 3 to 1 (3 dominate for everyone recessive) • From this he deduced the presence of genes and alleles • Homozygous- same allele • Heterozygous - different allele

5. Alleles - alternate forms of the same trait or gene • similar genes are arranged in a similar orger in a chromosome, the location is called a locus • since 2 alternate forms are present we describe them with capital (dominant) and lower case (recessive) letters • In a homologous pair a dominant allele masks the presence of a recessive allele

6. Homozygous with dominant • Homozygous with recessive • Heterozygous ? • Genotype refers to the genetic makeup of an individual • Phenotype refers to the actual expression of the genetic makeup

7. Mendel’s Principles of Inheritance • Inherited traits are transmitted by genes which occur in alternate forms called alleles • Principle of Dominance - when 2 forms of the same gene are present the dominant allele is expressed • Principle of Segregation - in meiosis two alleles separate so that each gamete receives only one form of the gene • Principle of Independent Assortment - each trait is inherited independent of other traits (chance)

8. Punnett’s Square B b B b

9. Assignment • Draw a Punnett square for 2 genes • Use Bb for hair color and Ee for eye color