Mendel and the Gene

Mendel and the Gene - Chapter 13: Mendel and the Gene The...

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Chapter 13: Mendel and the Gene The theory of evolution by natural selection clarifies why species change through time. The chromosome theory of inheritance explained how genetic information is transmitted from one generation to the next. An Austrian monk named Gregor Mendel worked out the rules of inheritance through a series of experiments on garden peas. Genetics is the branch of biology that focuses on the inheritance of traits. I. Mendel’s Experimental System A trait is any characteristic of an individual, ranging from height to primary structure of a particular membrane protein. a. What Questions was Mendel Trying to Answer? i. What are the basic patterns in the transmission of traits from parent to offspring? ii. Blending Inheritance 1. Claimed that the traits observed in a mother and father blend together to form the traits observed in their offspring. As a result, an offspring’s traits are intermediate between the mothers and fathers traits. When a black sheep and white sheep mate, their hereditary determinants blend to form a new hereditary determinant for grey wool. iii. Inheritance of acquired characters 1. Claimed that traits present in parent are modified, through use, and passed on to their offspring in the modified form. Giraffes extend their necks by straining to reach leaves high in the tops of trees, they subsequently produce longer-necked giraffe. b. Garden Peas Served as the First Model Organism in Genetics Peas are inexpensive and easy to grow from seed, have a relatively short generation time, and produce reasonably large numbers of seeds. This feature made is possible for Mendel to continue experiments over several generations and collect date from large numbers of individuals. Peas served as a model organism: a species that is used for research because it is practical and because conclusions drawn from studying it turn out to apply to many other species as well. Two additional features of the pea made it possible for Mendel to design his experiments: He could control which parents were involved in a mating and he could arrange mating between individuals that differed in easily recognizable traits, such as flower color or seed shape. i. How Did Mendel Control Mating? 1. Sperm cells are produced in pollen grains, which are small sacs that mature in the male reproductive structure of the plant. Eggs are produced in the female reproductive structure. Normally garden peas would self fertilize but Mendel removed the male reproductive system and transferred pollen from a different plant (cross-fertilization). 2. Mendel cut the pollen from one plant so that it only contained the female reproductive system. He then cross pollinated it with the pollen of a different plant. ii.
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This note was uploaded on 03/16/2011 for the course BIO 180 taught by Professor Chamberlain during the Spring '08 term at Staten Island.

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Mendel and the Gene - Chapter 13: Mendel and the Gene The...

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