MENDEL & MEIOSIS

Gregor Mendel Austrian Monk 1822-1884 Father of Genetics

Genetics Branch of biology that studies heredity.

Heredity The passing on of characteristics from parents to offspring.

Traits Characteristics that are inherited Eye color Size Hair, skin color etc.

Choosing a subject Mendel chose garden peas because Easy to grow Produce many offspring Can be self-pollinated

See drawing of typical flower Garden peas produced both egg and sperm. Gametes - sex cells

Pollination - transfer of male pollen grains to pistil of flower. Self pollination - occurs when pollen is transferred to the pistil of the same flower or plant.

Cross pollination - occurs when the pollen of one plant is transferred to the pistil of a different plant.

Fertilization - the uniting of the male and female gametes.

Pure breed - an organism that is true breeding for a trait. Hybrid - offspring of parents that have different forms of a trait.

Monohybrid crosses - A cross between two parents differing by one trait. See example.

Seven Traits Seed shape, Seed color Flower color, Flower position Pod color , Pod shape Plant height

Mendels Principles Principle of Dominance Principle of Segregation Principle of Independent assortment

Principle of Dominance One gene in a pair may mask the other gene, preventing it from having an effect.

Principle of Segregation The two factors for a characteristic segregate or separate during formation of eggs and sperm.

Principle of Independent Assortment Traits are inherited independently of each other.

Allele Different manifestation of a trait. Example: Trait = height Different manifestations are tall and short.

Phenotype Outward manifestation of a trait. It is what you see. The plant is: Tall, Blue, smelly, etc.

Genotype Actual gene combination from both parents. Example: TT, Tt, tt.

Homozygous Both alleles for a trait are the same. Example: tt, TT

Heterozygous The two alleles for a trait differ from one another. Example: Tt

Monohybrid cross A cross between two parents differing by a single trait. Example: short pea plant crossed to a tall pea plant

Dihybrid cross A cross between two parents involving two different traits. Example: Round yellow seeds crossed to wrinkled green seeds.

Reginald Punnett, 1905 Developed the Punnett square. Shortcut method for finding expected proportions of possible genotypes.

Calculating probability Divide the number of desired outcomes by the total number of possible outcomes. Example: Heads or tails = 2 possible outcomes. Heads desired = 1 desired outcome. 1/2 =1:2

Test cross Used to determine if an organism is homozygous dominant or heterozygous. Cross the unknown with a homozygous recessive.