BIG IDEAS Traits and Heredity Gregor Mendel Punnett

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

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

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

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

� 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.

� 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.

� 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.

� 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 CROSSPOLLINATED, MENDEL REMOVED THE ANTHERS SO THE PLANTS COULD NOT SELF-POLLINATE! � Then, he used the pollen from another plant to fertilize the plant.

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

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

� 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.

v v v 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… v. GREAT JOB MY JUNIOR GENETICISTS!!! So proud of you!