Mendel’s Laws of Heredity Spring 2017

What are different forms of genes called? Question What are different forms of genes called? Answer: Alleles

Mendel’s Laws of Heredity Mendel concluded that: Biological inheritance is determined by factors. Factors are passed from one generation to the next. These factors that determine traits are called genes.

Mendel’s Laws of Heredity Alleles are different forms of genes. Example: A gene for height can produce genes for tall plants genes for short plants

Mendel’s 1st Law of Heredity Law of Segregation Every organism has two alleles of each gene When gametes are produced, the alleles separate. RECALL gametes are male and female sex cells

Mendel’s Laws of Heredity Phenotype The way an organism looks and behaves. Its what an organism PHYSICALLY looks like. Examples: Tall or short plants Purple or white flowers Green or yellow peas Round or wrinkled seeds

Mendel’s Laws of Heredity Genotype The allele combination of an organism Letter representation of alleles 3 ways to write a genotype: 2 capital letters 1 capital letter, 1 lower case 2 lower case letters

Mendel’s Laws of Heredity An organism is homozygous for a trait if the two alleles for the trait is the SAME TT- homozygous dominant tt- homozygous recessive Tt- heterozygous (homo means the same, hetero means different.)

Mendel’s 2nd Law of Heredity Law of Independent Assortment- Genes for different traits are inherited independently of each other. Alleles for a trait separate when gametes are formed. In a dihybrid cross (two traits) you can see both of Mendel’s laws at work.

Heredity