Chapter 6: Introduction to Genetics Section 6-1: The Science of Inheritance and Gregor Mendel

Parents and Offspring Heredity = biological inheritance An organism’s heredity is the set of characteristics it receives from its parents. Genetics is the study of heredity. Heredity IS NOT just a blend of characteristics from both parents – look at page 124

Gregor Mendel Born in 1822, became a monk, but also studied science and math in Vienna In the monastery, Mendel’s job was to take care of the garden (monasteries are self-sustaining) He took an interest in pea plants – he began with true-breeding stock

True-Breeding Stock True-breeding stock refers to individuals that always pass on their characteristics to the next generation (ex. a tall pea plant with green pods will ALWAYS produce tall pea plants with green pods)

Reproduction in Pea Plants Peas use their flowers to reproduce (p.125) Male sex cell = pollen Female sex cell = egg Pea plants normally self-pollinate, meaning the pollen and egg come from the same plant (basically only one parent) True-breeding stock results from generations of self-pollination

Mendel and Pea Plants Mendel wanted to see what would happen if he crossed true-breeding stock with different characteristics Mendel removed all the male plant parts so that he could control pollination, making sure that pollen and egg came from different plants This is called cross-pollination

Mendel’s Seven Traits Trait = characteristic that identifies one individual from another Mendel focused on seven traits, each with two contrasting forms

Mendel’s Seven Traits Trait Form 1 Form 2 Seed shape Round Wrinkled Seed color Yellow Green Seed coat color Gray White Pod shape Smooth Constricted Pod color Flower position Axial Terminal Plant height Tall Short

Mendel’s Seven Traits Mendel used true-breeding stock to create hybrids – offspring of parents with different characteristics The hybrids were called the first filial generation (F1 generation) and the true-breeding stock were called the parental generation (P generation)

Mendel’s Seven Traits Mendel noticed the traits seen in the F1 generation were not a blending of the P generation’s traits The traits of only ONE parent appeared in the offspring while the traits of the other parent seemed to disappear