TAILIEUCHUNG - Lecture Biology 25 (Human Biology): Chapter 19, 20 - Prof. Gonsalves
Chapter 19, 20 includes contents: History of genetics, modern genetics, Mendel’s experiments, summary of Mendel’s results, Mendel’s conclusions, principles of Mendelian genetics, the stages of cell division, separation of homologous chromosomes,. | Chapter 19 & 20 Biology 25: Human Biology Prof. Gonsalves Los Angeles City College Based on Mader’s Human Biology,7th edition and Fox’s 8th ed Powerpoints Heredity: The transmission of traits from one generation to another. Variation: Offspring are different from their parents and siblings. Genetics: The scientific study of heredity and hereditary variation. Involves study of cells, individuals, their offspring, and populations. I. History of Genetics Blending Hypothesis: In 1800s biologists and plant breeders suggested that traits of parents mix to form intermediate traits in offspring. Parents Offspring Red flower x White flower Pink flower Tall height x Short height Medium height Blue bird x Yellow bird Green birds Fair skin x dark skin Medium skin color If blending always occurred, eventually all extreme characteristics would disappear from the population. Gregor Mendel: Established genetics as a science in 1860s. Considered the founder of modern genetics. II. Modern Genetics Began as a science in 1860s. Gregor Mendel: An Austrian monk, who was a farmer’s son. He was trained in mathematics, chemistry, and physics. Studied the breeding patterns of plants for over 10 years. Artificially crossed peas, watermelons, and other plants. Kept meticulous records of thousands of breedings and resulting offspring. Rejected blending hypothesis, and stressed that heritable factors (genes) retain their individuality generation after generation. II. Modern Genetics Gregor Mendel: Calculated the mathematical probabilities of inheriting many genetic traits. Published results in 1866. They were largely ignored due to fervor surrounding Darwin’s publications on evolution. Discouraged by the lack of attention from the scientific community, he quit his work and died a few years later. Importance of Mendel’s work was not appreciated until early 1900s when his paper was rediscovered. III. Mendel’s Experiments Used “true-breeding” or purebred plant varieties for seven pea .
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