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12.1: Origins of Hereditary Science Objectives • Why was Gregor Mendel important for modern genetics? • Why did Mendel conduct experiments with garden peas? • What were the important steps in Mendel’s first experiments? • What were the important results of Mendel’s first experiments? Mendel’s Breeding Experiment • Gregor Mendel • A monk that did breeding experiments in the 1800s with the _______________________________ • The science of __________________ and the mechanism by which traits are passed from parents to _____________________ is called __________________. • ____________________________ is based on Mendel’s explanations for the patterns of heredity in garden pea plants. • Most of Mendel’s experiments involved crossing ______________ types of pea plants. In this case, the words ___________ means “to mate or breed two individuals.” Features of Pea Plants • The garden pea plant is a good subject for studying heredity because the plant has: • • • • In the study of heredity, physical features that are inherited are called ____________________. • A _____________is one of several possible forms of a character. • The offspring of a cross between parents that have contrasting traits is called a _________________. • In garden pea plants, each flower contains both ___________ and ______________ reproductive parts. This arrangement allows the plant to ___________________________, or fertilize itself. • ___________________________ occurs when ____________ from the flower of one plant is carried by insects or by other means to the flower of _____________________________. • Mendel cross-pollinated pea plants by removing the _________________ from some of the flowers then dusting the female parts with _________ from another plant. Features of Pea Plants (cont.) • The garden pea is a good subject for studying heredity because it _________________________________ and produces _______________________________. • Thus, Mendel was able to compare several results for each type of cross and collect repeated data. • Collecting repeated data is an important scientific method. Checkpoint • Who is called the father of genetics? • What did he study? – Why? • What is the difference between self and cross pollination? • What is a hybrid? Mendel’s First Experiment • A ______________________ is a cross that is done to study _________ pair of contrasting traits. • Ex.: Crossing a plant that has purple flowers with a plant that has white flowers. • Mendel’s first experiments used monohybrid crosses and were carried out in three steps. • Each step involved a new generation of plants. A _________________ is a group of offspring from a given group of parents. • Plants that _______________ for several generations produce offspring of the same type. Such a plant is said to be _______________________ for a given trait. • The first group of parents that are crossed in a breeding experiment are called the ________________________ or P generation. The offspring of the P generation is called the first filial generation, or ______________________. • Mendel allowed the F1 generation to _______________________ and produce new plants. He called this offspring the second filial generation, or _________________________. Ratios in Mendel’s Results • All of Mendel’s F1 plants expressed the __________ trait for a given character. The contrasting trait seemed to have _____________________. • The contrasting trait _______________________, however, in some of the F2 plants when the F1 plants were allowed to self-pollinate. • For each of the seven characters that Mendel studied, he found a similar _______ ratio of contrasting traits in the F2 generation. Checkpoint • What are two reasons garden peas good to study heredity? • What is a monohybrid cross? • What is true breeding? • How are the p, f1 and f2 generations related? • Which generation does the recessive trait disappear and which generation does it reappear? • What is the ratio of the f2 generation? Summary • Modern genetics is based on Mendel’s explanations for the patterns of heredity that he studied in garden pea plants. • The garden pea plant is a good subject for studying heredity because the plant has contrasting traits, usually self-pollinates, and grows easily. • Mendel’s first experiments used monohybrid crosses and were carried out in three steps. • For each of the seven characters that Mendel studied, he found a similar 3-to-1 ratio of contrasting traits in the F2 generation.