1. BIG IDEAS: Traits and Heredity Gregor Mendel Punnett Square Cross Pollination of Flowers

2.  Mendel was a monk who taught science and performed many experiments.  Mendel discovered the principles of heredity in the monastery garden.

3.  Mendel worked with plants and knew that inheritance patterns were not always clear.  EXAMPLE: Sometimes a trait that appeared in one generation (parents) was not present in the next generation (offspring).  BUT in the generation AFTER that the trait appeared.

4.  Mendel chose pea plants.  Pea plants were able to self-pollinate.  A self-pollinating plant has both male and female reproductive structures

5.  Eggs (in an ovule) and sperm (in pollen) from the same plant combine to make a new plant.  Mendel was able to grow true-breeding plants.  When true-breeding plants self- pollinates, all of its offspring will have the same traits.  EXAMPLE: A true-breeding plant with purple flowers will have offspring with purple flowers.

6.  Pea plants can also cross-pollinate.  Cross pollination: pollen from one plant fertilizes the ovule of a flower on a different plant.  Pollen can be carried by insects to a flower on a different plant.  Pollen can be carried by the wind from one flower to another.

8.  CHARACTERISTIC: a feature that has different forms in a population.  EXAMPLE: Hair color, eye color, skin color.  TRAITS: The different forms of these characteristics.  Mendel used different traits to study heredity.  He chose purple flowers and white flowers.

9.  Mendel used true breeding plants.  He decided to find out what would happen if he bred, or crossed, two plants that had different traits.  TO BE SURE THAT THE PLANTS CROSS- POLLINATED, MENDEL REMOVED THE ANTHERS SO THE PLANTS COULD NOT SELF-POLLINATE!  Then, he used the pollen from another plant to fertilize the plant.

10.  Mendel crossed purple flowers with white flowers.  RESULTS: All the offspring were purple.  Dominant Trait: Purple Flower  Recessive Trait: White Flower

11.  Mendel allowed the first-generation of plants to self-pollinate.  The recessive trait of the white flower reappeared in the second generation.

12.  The recessive trait did not show up as often as the dominant trait.  Mendel decided to figure out the ratio of dominant traits to recessive traits.  A ratio is a relationship between two different numbers that is often expressed as a fraction.  Look at page 60 and calculate the ratios for each of those plants that Mendel crossed pollinated.

13.  I can tell you that a recessive trait is…  I can tell you that a dominant trait is…  I can tell you what cross- pollination is…  I can tell you what true-breeding is…  I can tell you what a Punnett Square is…  GREAT JOB MY JUNIOR GENETICISTS!!! So proud of you!