Genetics

What is Genetics?  Heredity: The passing of traits from parents to offspring.  Genetics: the scientific study of heredity.

Gregor Mendel  Born in 1822  When he was 21 he entered an Augustinian monastery, where he became a math and science teacher.  Began studying the plants.

Mendel’s Plant Height Experiment  Mendel started his experiment with pea plants.  Mendel used purebred plants.  A purebred plant is one that always produces offspring with the same form of a trait as the parent.

Mendel’s Plant Height Experiment 1. He bred pea plants so they always produce offspring with heights like parents:  Tall parent: tall offspring  Short parent: short offspring

Mendel’s Plant Height Experiment  Then, he bred a tall pea plant with a short pea plant  He found that the offspring were all tall.

Mendel’s Plant Height Experiment  Then he bred two of these tall offspring together  There were some tall and some short offspring.  This lead him to think that the peas had a trait for tallness and shortness.

Traits  He called them dominant and recessive traits.  A dominant trait is one that prevents another from appearing or showing themselves in the offspring  A recessive trait is one that will not appear when a dominant trait is present.

 An organism with a pure trait had ALL dominant or ALL recessive traits.  A pure bred is an organism that always produces offspring with the same form of a trait as the parent.

Mendel’s Peas  Mendel studied six other traits in pea plants.

Genes  Today we know Mendel’s traits as genes.  A dominant gene (represented by a capital letter) covers up or hides a recessive gene (represented by a lower case letter)

Genes  Genes are inherited in pairs – one gene from each parent.