Biology Chapter 12 Section 1

Key Ideas  Why was Gregor Mendel important for modern genetics?  Why did Mendel conduct experiments with garden peas?  What were the important steps in Mendel’s first experiment?  What were the important results of Mendel’s first experiment?

Mendel’s Breeding Experiments  Monk named Gregor Johann Mendel in the 1800’s in Austria.  Did breeding experiments with pea plants.  Modern genetics is based on Mendel’s explanations for the patterns of heredity in garden pea plants.

 He studied to be a priest. He went to the University of Vienna. He studies science.  Lived the rest of his life in a monastery, where he taught high school and cared for a garden.

 Most of Mendel’s experiments involved crossing different types of pea plants.  To cross means to mate or breed two individuals.  He crossed a plant with purple flowers with one that had white flowers. All of the offspring had purple flowers.  But when these flowers were crossed, some offspring had white flowers and some had purple flowers.

 Since the white flower reappeared in the second group (generation) he decided to investigate this strange occurrence.

Why Did He Use Pea Plants?  Contrasting Traits  Self-Pollination  Easy to Grow

Contrasting Traits  Physical features that are inherited are called characters.  A trait is one of several possible forms of a character.  The offspring of a cross between parents that have contrasting traits is a hybrid.

Self-Pollination  Each pea plant contains male and female reproductive parts. This allows them to self- pollinate.  The can also reproduce by cross-pollination. This happens when pollen from one pants is carried by insects or other means to the flower of another plant.  To make sure the plants couldn’t self- pollinate, he removed the male parts but did not remove the female parts. He dusted the female parts with pollen from another plant.

Easy to Grow  The small plants that need little care and they mature quickly.  They also produce many offspring.

7 Characters Studies By Mendel  Flower Color  Seed Color  Seed Shape  Pod Color  Pod Shape  Flower Position  Plant Height

Mendel’s First Experiment  Carried it out with a monohybrid cross (one purple and one white)  He allowed each one to self-pollinate first and create a “true-breed”. They are called the parental generation (P generation).  Then he crossed 2 P generation plants and called the offspring the first filial generation (f1 generation)

 He allowed the f1 generation to self- pollinate and produce new plants. He called them f2 generation.  He discovered that in the f2 generation the white flowers reappeared.

Ratios in Mendel’s Results  For each of the 7 characters that Mendel studies, he found a 3-to-1 ratio of contrasting traits in the f2 generation.