Human Diseases A Systemic Approach CHAPTER 5 Heredity and Disease Human Diseases A Systemic Approach Seventh Edition Mark Zelman Elaine Tompary Jill Raymond Paul Holdaway and Mary Lou Mulvihill Copyright 2010 by Pearson Education Inc Upper Saddle River New Jersey 07458 All rights reserved Chapter 5 Objectives Describe DNA s composition and its role in heredity Describe general mechanisms of transmission of hereditary diseases and give examples Explain genetic diseases based on abnormal chromosome construction Highlight Down Syndrome Discuss screening techniques and the concept of gene therapy Distinguish between congenital and hereditary conditions Human Diseases A Systemic Approach Seventh Edition Mark Zelman Elaine Tompary Jill Raymond Paul Holdaway and Mary Lou Mulvihill Copyright 2010 by Pearson Education Inc Upper Saddle River New Jersey 07458 All rights reserved Heredity The Basics DNA the blueprint for directing cell activities Chromosomes assembled strands of DNA within the nucleus 44 autosomes 22 pairs 2 sex chromosomes Female XX Male XY Karyotype the complete chromosomal composition Human Diseases A Systemic Approach Seventh Edition Mark Zelman Elaine Tompary Jill Raymond Paul Holdaway and Mary Lou Mulvihill Copyright 2010 by Pearson Education Inc Upper Saddle River New Jersey 07458 All rights reserved Chromosomes can be extracted from the nucleus photographed under a microscope in order to detect abnormalities Figure 5 3 Normal human karyotype Custom Medical Stock Photo Human Diseases A Systemic Approach Seventh Edition Mark Zelman Elaine Tompary Jill Raymond Paul Holdaway and Mary Lou Mulvihill Copyright 2010 by Pearson Education Inc Upper Saddle River New Jersey 07458 All rights reserved Genetic Inheritance Genes for a particular trait e g hair color occupy a particular site on a chromosome Each person has 2 copies of each gene 1 from each parent Alleles alternate forms of a gene Homozygous the same e g BB or bb Heterozygous different e g Bb Dominant when only one allele is need to express a trait e g Bb results in brown hair Recessive when two are needed to express a trait e g the red hair allele is recessive Human Diseases A Systemic Approach Seventh Edition Mark Zelman Elaine Tompary Jill Raymond Paul Holdaway and Mary Lou Mulvihill Copyright 2010 by Pearson Education Inc Upper Saddle River New Jersey 07458 All rights reserved Autosomal Dominant Diseases Occur through transmission of a dominant allele Offspring have 50 chance of being affected if one parent has normal karyotype Males and females have equal chance of being affected Human Diseases A Systemic Approach Seventh Edition Mark Zelman Elaine Tompary Jill Raymond Paul Holdaway and Mary Lou Mulvihill Copyright 2010 by Pearson Education Inc Upper Saddle River New Jersey 07458 All rights reserved Doesn t mean if you have 4 kids that 2 will have the disease Know how to do these for exam Figure 5 4 Transmission of autosomal dominant disorders 50 chance for an affected child Human Diseases A Systemic Approach Seventh Edition Mark Zelman Elaine Tompary Jill Raymond Paul Holdaway and Mary Lou Mulvihill Copyright 2010 by Pearson Education Inc Upper Saddle River New Jersey 07458 All rights reserved Examples of Autosomal Dominant Diseases Polydactyly Achondroplasia Results in very short person Abnormal cartilage formation Marfan syndrome The connective tissue protein fibrillin is missing Results in very tall person Lincoln Familial hypercholesterolemia Human Diseases A Systemic Approach Seventh Edition Mark Zelman Elaine Tompary Jill Raymond Paul Holdaway and Mary Lou Mulvihill Copyright 2010 by Pearson Education Inc Upper Saddle River New Jersey 07458 All rights reserved Autosomal Recessive Diseases Disease manifests when individual is homozygous for the defective allele Heterozygous parents are carriers they do not have the disease Child has a 25 chance of being affected Recessive allele appears more frequently in close intermarriages Human Diseases A Systemic Approach Seventh Edition Mark Zelman Elaine Tompary Jill Raymond Paul Holdaway and Mary Lou Mulvihill Copyright 2010 by Pearson Education Inc Upper Saddle River New Jersey 07458 All rights reserved Figure 5 6 Transmission of recessive disorders 25 chance for an affected child Human Diseases A Systemic Approach Seventh Edition Mark Zelman Elaine Tompary Jill Raymond Paul Holdaway and Mary Lou Mulvihill Copyright 2010 by Pearson Education Inc Upper Saddle River New Jersey 07458 All rights reserved Examples of Autosomal Recessive Diseases Phenylketonuria PKU Missing enzyme Phenylalanine Hydroxylase Human Diseases A Systemic Approach Seventh Edition Mark Zelman Elaine Tompary Jill Raymond Paul Holdaway and Mary Lou Mulvihill Newborns are screened immediately If trait is found a synthetic diet is offered e g Lofenalac which greatly reduces risk Copyright 2010 by Pearson Education Inc Upper Saddle River New Jersey 07458 All rights reserved More Examples of Autosomal Recessive Diseases Sickle cell anemia The black population most at risk 1 in 12 are carriers Hemoglobin is abnormal results in deformed red blood cells Deformed cells lodge and block circulation SUPER INTERESTING FACT Heterozygous individual does not have the disease but will experience mild anemia BUT The defective allele confers increased resistance to Malaria 2 which kills million people a year http www youtube com watch v 2CsgXHdWqVs watch Human Diseases A Systemic Approach Seventh Edition Mark Zelman Elaine Tompary Jill Raymond Paul Holdaway and Mary Lou Mulvihill Copyright 2010 by Pearson Education Inc Upper Saddle River New Jersey 07458 All rights reserved More Examples of Autosomal Recessive Diseases Galactosemia Tay Sachs disease Albinism Research one of these for exam Human Diseases A Systemic Approach Seventh Edition Mark Zelman Elaine Tompary Jill Raymond Paul Holdaway and Mary Lou Mulvihill Copyright 2010 by Pearson Education Inc Upper Saddle River New Jersey 07458 All rights reserved Sex Linked Inheritance Defective gene on X chromosome Y chromosome is small and carries few genes Defective X on male is unmasked so the trait is expressed Far less common for females to inherit x linked diseases Heterozygous female is carrier for the disease Male transmits the defective allele to his daughters Human Diseases A Systemic Approach Seventh Edition Mark Zelman Elaine Tompary Jill Raymond Paul Holdaway and Mary Lou Mulvihill Copyright 2010 by Pearson Education Inc Upper Saddle River New Jersey