I. Gregor Mendel A. Mendel performed 1 st experiments in heredity -the passing on of characteristics from parents to offspring. B. Mendel’s work founded Genetics - the study of heredity. 1. Characteristics that are inherited are called traits

C. Mendel used pea plants during his experiments. 1. Pea plants reproduce sexually. 2. Sex cells are called gametes 3. Male gamete – pollen. 4. Female gamete - ovule D. Pollination- transfer of the male pollen grains to the female ovule.

E. In Mendel’s experiments, he would sometimes take pollen from one plant and place it on the ovule of another plant. 1. This is called cross-pollination

II. Mendel’s Monohybrid Crosses A. Mendel crossed tall pea plants with short plants. 1. This cross is known as a hybrid. 2. Hybrid-offspring of parents that have different traits.

B. Mendel's results – all tall plants, F 1 generation 1. F stands for son or daughter. a. F 1 = First Generation b. F 2 = Second Generation C. Mendel’s F 2 generation. Some tall, some short

III. Rules and Laws of Heredity A. The rule of unit factors-two factors control an organisms traits. B. These factors are called Genes 1. Genes are located on chromosomes. 2. Different types of genes are called alleles.

Example: A pea plant could have : one allele for tallness and one for shortness two alleles for tallness or shortness.

3. An organism receives one allele from the male parent, and one allele from the female parent. C. The rule of dominance-alleles are either dominant or recessive. In pea plants, tallness is dominant to shortness. Shortness in this example is recessive.

1. A tall plant can have: a. One allele for tallness and one allele for shortness. b. Two alleles for tallness. 2. A short plant can only have two alleles for shortness.

D. When recording the results of crosses, we often use the 1 st letter of the genes we are crossing. A tall plant could have the following alleles: TT or Tt A short plant could have the following alleles: tt E. The law of segregation-gametes randomly pair up.

IV. Genotypes and Phenotypes A. Organisms can look alike, but have different genes. 1. The way an organism looks is known as it’s phenotype The phenotype of a tall plant is TALL B. The combination of alleles is the genotype 1. A tall plants genotype can be TT or Tt.

2. You can never know for sure an organisms genotype given it’s phenotype. 3. An organism is homozygous if it’s alleles are the same. TT or tt

4. An organism is heterozygous if it has one dominant allele and one recessive allele. Tt