Section 1 Mendel and His Peas Key Concept  The work of Gregor Mendel explains the rules of heredity and is the foundation of modern genetics. What You Will Learn • Heredity is the passing of genetic traits from parent to offspring. Gregor Mendel’s experiments with pea plants led to the discovery of dominant and recessive traits. Why It Matters Heredity explains why you have many of your traits.

heredity The passing on of traits from parents to offspring. These traits are passed on in genes.

Mendel Gregor Mendel was an Austrian monk who grew up on a farm and learned a lot about flowers and fruit trees. His favorite thing to study was pea plants. He performed experiments about heredity and established the science of genetics.

A trait that always appears whenever it is present A trait that always appears whenever it is present. Traits are carried in genes. dominant trait

recessive trait A trait that does not appear if there are genes for the dominant trait. It appears when there are two recessive genes.

1. Heredity is the passing of traits from parents to offspring. 2.Before Mendels ideas were accepted, people explained inheritance as the blending of traits from each parent. 3. Gregor Mendel’s experiments using pea plants eventually changed the way people thought about heredity. 4. When parents with different traits are bred, dominant traits are always present in the first generation. Recessive traits are not visible in the first generation but reappear in the second generation. 5. Mendel found a 3:1 ratio of dominant-recessive traits in the second generation. 6. Mendel’s ideas are the foundation of modern genetics.