Ch. 2 Outline

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Unformatted text preview: 1/4 x ¼ x ¼ x ¼ )+( 1/4 x ¼ x ¼ x ¼ ) = 2/256 Rediscovery of Mendel Rediscovery of Mendel Mendel’s work was unappreciated and remained dormant for 34 years Even Darwin’s theories were viewed with skepticism in the late 1800’s because he could not explain the mode of inheritance of variation In 1900, 16 years after Mendels died, three scientists rediscovered and acknowledged Mendel’s work, giving birth to the science of 1900 ­ Carl Correns, Hugo deVries, 1900 ­ Carl Correns, Hugo deVries, and Erich von Tschermak rediscover and confirm Mendel’s laws Mendelian inheritance in humans Mendelian inheritance in humans Most traits in humans are due to the interaction of multiple genes and do not show a simple Mendelian pattern of inheritance A few traits represent single­genes. Examples include sickle­cell anemia, cystic fibrosis, Tay­Sachs disease, and Huntington’s disease (Table 2.1) In 2009, there were ~4300 single­gene traits known in humans In humans, we usually examine large groups of people from a particular region, ethnic group, or controlled breeding to gain more information about a disease Some of the most common single­gene traits caused by recessive alleles in humans Disease Thallassemia (chromosome 16 or 11) Sickle-cell anemia (chromosome 11) Effect Incidence of Disease Reduced amounts of hemoglobin; 1/10 in parts of Italy anemia, bone, and spleen enlargement Abnormal hemoglobin; sickle1/625 Africanshaped red cells, anemia, blocked Americans circulation; increased resistance to malaria Defective cell membrane protein; excessive mucus production; digestive and respiratory failure Missing enzyme; buildup of fatty deposit in brain; buildup disrupts mental development Missing enzyme; mental deficiency 1/2000 Caucasians Cystic fibrosis (chromosome 7) Tay-Sachs disease (chromosome 15) Phenylketonuria (PKU) (chromosome 12) 1/3000 Eastern European Jews 1/10,000 Caucasians Table 2.1 Some of the most common single­gene traits Some of the most common single­gene traits caused by dominant alleles in humans Disease Hypercholesterolemia (chromosome 19) Huntington disease (chromosome 4) Effect Missing protein that removes cholesterol from the blood; heart attack by age 50 Progressive mental and neurological damage; neurologic disorders by ages 40 - 70 Incidence of Disease 1/122 French Canadians 1/25,000 Caucasians Table 2.1 In humans we must use pedigrees to In humans we must use pedigrees to study inheritance Pedigrees are an orderly diagram of a families relevant genetic features extending through multiple generations Pedigrees help us infer if a trait is from a single gene and if the trait is dominant or recessive Anatomy of a pedigree Anatomy of a pedigree A vertical pattern of inheritance A vertical pattern of inheritance indicates a rare dominant trait A horizontal pattern of inheritance A horizontal pattern of inheritance indicates a rare recessive trait How to recognize dominant traits in How to recognize dominant traits in pedigrees Three key aspects of pedigrees with dominant traits: 1. 1. 1. How to recognize recessive traits in pedigrees How to recognize recessive traits in pedigrees Four keys aspects of pedigrees with recessive traits: 1. 1. 1. 1....
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This note was uploaded on 02/22/2011 for the course BIOL 2153 taught by Professor Larkin during the Spring '03 term at LSU.

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