Chapter 13 Lecture Outline

Chapter 13 Lecture Outline - Biology 100 Vandan Desai...

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Biology 100 Vandan Desai Chapter 13: Mendel and the Gene (Lecture Outline) ---------------------------------------------------------------------------------------------------------------------------- I. Mendel’s Experiments with a Single Trait A. Genetics —branch of biology that focuses on heredity B. Heredity —inheritance or transmission of traits from parents to offspring C. Trait —any characteristic of an individual D. Gregor Mendell —interested in basic patterns governing transmission of traits from parents to offspring (work precedes Darwin & understanding of meiosis, genes, etc) E. Hypotheses to explain how traits are transmitted from parent to offspring i. Blending Inheritance Hypothesis (favored by Nägeli, mentor of Mendell) a. Claimed that the traits observed in mother and father blend together to form the traits observed in their offspring b. Example: white sheep mates w/ black sheep, producing gray offspring ii. Inheritance of Acquire Characteristics Hypothesis (proposed by Lamarck & favored by Darwin ) a. Traits present in the parents are modified through use and passed on to their offspring in the modified form b. Example: adult giraffes strain their necks to reach food in trees, necks become longer, and their offspring inherit the longer neck trait F. Mendel chose an appropriate model organism to study i. Consists of individuals that are usually small, short lived, inexpensive to care for, prolific in producing offspring, and easy to manipulate experimentally ii. Conclusions drawn from studying them turn out to apply to other organisms G. Mendel chose the pea plant Pisum sativum as first model organism in genetics i. Can self-fertilize ; contain both male/female reproductive organs ii. Sperm cells produced in pollen grains ( anther —male reproductive structure) iii. Eggs produced in pistil —female reproductive structure iv. Fertilization begins when pollen grains are deposited on a tube-like section of the female reproductive organs H. Self-fertilization —pollen from one flower falls on female organs of the same flower I. Cross-pollination —remove male reproductive parts from a flower before any pollen formed to prevent self-fertilization and deposit pollen from another flower on that flower’s female reproductive organ; allowed Mendel to control mating of organism J. Mendel studied seven different traits in pea plants: seed shape, seed color, pod shape, pod color, flower color, flower and pod position, and stem length i. Each trait exhibited one of two forms ; two phenotypes —observable traits K. Obtained individuals from pure/true-breeding lines —individuals produce offspring identical to themselves when self-pollinated or crossed to another of same population L. Inheritance of a Single Trait—crossing pure lines that differed in only one trait i. Parental generation —adults used in initial experimental cross ii. F 1 generation —offspring of the parental generation iii. When two true-breeding pea plants (round vs. wrinkled seeds) are crossed, all of the offspring are round seeded iv. Reciprocal crosses demonstrated that the inheritance of seed shape is not affected
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This note was uploaded on 03/08/2010 for the course BIOL 100 taught by Professor Staff during the Fall '07 term at UMBC.

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Chapter 13 Lecture Outline - Biology 100 Vandan Desai...

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