Inheritance and Genetics

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

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

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

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

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

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)

B b BbBb Punnett’s Square

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