Mendel and His Peas 5.1

Early Ideas About Heredity Heredity is the passing of traits from parents to offspring. Gregor Mendel (Father of Genetics) Genetics – the study of how traits are passed from parents to offspring.

Mendel’s Experimental Methods Mendel used pea plants for his experiments because they reproduce quickly, easily observed traits (flower color), control of plant reproduction. Pollination occurs when pollen (male plant reproductive organ) lands on the pistil (female plant reproductive organ) of a flower. 2 types of pollination: Cross-pollination (2 separate plants) and self pollination (same plant)

Pollination in Pea Plants Cross Pollination occurs naturally with wind, water, or animals. Mendel allowed one group of flowers to self pollinate and then he cross pollinated the plants himself. He used True breeding plants for each trait.

Mendel Pea Traits

True Breeding Plants True Breeding plants produce offspring with traits that match the parent. Ex. True breeding purple pea plants can only produced purple pea plants. Mendel cross pollinated true breeding plants to discover which traits were predictable.

Mendel’s Results Mendel realized as he crossed a true breeding purple with a true breeding white plant that all the offspring had purple flowers. He referred to the cross pollination of the purple x white as the parent generation The offspring of the parent generation are referred to as the first generation or F₁. These plants were considered hybrid (coming from true breeding plants with different forms of the same trait).

Second Generation Plants Mendel allowed the F₁ generation to self pollinate and 3 of the offspring were purple and 1 of the offspring were white. The offspring of the F₁ generation is called the second generation or F₂. He recorded all of his data and continued to cross pollinate more true breeding plants for different traits. The more data he collected the more precise his analysis was.

Mendel’s Conclusion He concluded that 2 genetic factors control each inherited trait. Also, that each reproductive cell (sperm and egg) contributes one factor for each trait.

Dominant & Recessive Traits Dominant Trait- is a genetic factor that blocks another genetic factor. Usually shows up in the first generation (F₁). Ex. Purple flower Recessive Trait – is a genetic factor that is blocked by the presence of a dominant factor. Usually shows up in the second generation (F₂). Ex. White flower.