9.1 Mendel’s Legacy : “Father of Modern Genetics”

Mendel Experimented with pea plants to figure out how different traits were inherited. He initially observed that tall plants usually produced other tall plants. However, they could also produce a short plant. Heredity - the transmission of characteristics from parents to offspring.

Mendel Mendel followed 7 different characteristics in pea plants. Trait - a genetically determined variant of a characteristic.

Controlling the Experiment Before Mendel could experiment, he had to control the way that plants reproduced. Pollination - pollen from anthers transfers to stigma. Self-Pollination - pollen is accepted from the same plant. Cross-Pollination - pollen is accepted from a different plant.

Mendel’s Experiment 3 Steps: 1)Produce “true-breeding” plants: “True breeding” - always passes down its own traits when self-pollinated. 2)Cross-pollinate opposing traits: Produces first filial generation “F 1 generation” 3)Self-Pollinate the F 1 Generation: Produces second filial generation “F 2 generation”

Conclusions For each individual trait, an individual has two copies of the gene - one from each parent There are alternative versions of genes (called alleles)

Conclusions When two alleles occur together, one of them may be completely expressed, while the other may have no observable effect on the organism’s appearance Dominant: Trait that is expressed Recessive: Trait that is expressed only when both recessive alleles represent

Conclusion cont. Law of Segregation: –An inheritable trait (gene) is controlled by a pair of alleles, which separate when making gametes. –No gamete will have two alleles for the same trait

Conclusion cont. Law of Independent Assortment: –The inheritance of one trait has no effect on the inheritance of another trait. –Ex: There is no relation between a cat’s color and tail length. –Only applies to traits located on separate chromosomes or far apart on the same chromosome.