Chapter 9 – Fundamentals of Genetics Section 1: Mendel’s Legacy Section 2: Genetic Crosses

Section 1: Mendel’s Legacy Gregor Mendel is considered to be the Father of Genetics. He was a monk that taught mathematics and that spent lots of his time in his garden studying and observing the many characteristics of his plants – especially garden peas. He observed 7 different characteristics of pea plants: Plant height Flower position on stem Pod color Pod appearance Seed texture Seed color Flower color A trait is a genetically determined characteristic. Mendel collected seeds from his pea plants and carefully recorded each plant’s traits and seeds. The next year he planted the seeds and kept track of what grew and observed all the characteristics.

Pea plants normally reproduce through self-pollination. Mendel carefully controlled how the pea plants were pollinated and observed what traits were expressed in the plants that grew from the seeds. Pollination – occurs when the pollen grains of the anthers (male) are transferred to the stigma (female). Self-pollination – occurs when the pollen from a plant lands on the stigma of the same plant. Cross-pollination- occurs when the pollen from one plant lands on the stigma of a different plant. Pea plants normally reproduce through self-pollination. Self-pollination can be prevented by removing all the anthers from a plant. You complete cross-pollination by using the anthers from a different plant to transfer pollen to the antherless plant. Mendel selected plants for specific traits and observed traits found in the offspring.

Definitions True-breeding – plants or animals that always produce offspring with the trait desired through self-pollination. P generation – the true-breeding parent generation. F₁ generation (first filial) – the offspring of cross-pollinating the true-breeding P generation. F₂ generation (second filial) – the offspring of self-pollinating F₁ generation. Dominant trait Recessive trait Law of Segregation Law of Independent Assortment Molecular Genetics