© 2011 McGraw-Hill Higher Education. All rights reserved.

Chapter Two

Your Family Health History

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Creating a Family Health Tree

• Also called a genogram or genetic pedigree

• Visual representation of your family’s genetic history

• Illustrates the patterns of health and illness within a family

• Pinpoints areas of special concern or risk for you

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Sample Family Health Tree

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What can you learn from your family health tree?

• An early onset of disease is more likely to have a genetic component

• The appearance of a disease in multiple individuals on the same side of the family is more likely to have a genetic correlation

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What else can you learn from your family health tree?

• A family member with multiple cancers represents a greater likelihood of a genetic association

• The presence of disease in family members who have good health habits is more suggestive of a genetic cause than is disease in members with poor health habits

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You and Your Genes: The Basics of Heredity

• The nucleus of every human cell contains an entire set of genetic instructions stored in our DNA (deoxyribonucleic acid)

• DNA has four building blocks that can be arranged to form a distinct message (gene) that acts as the body’s instruction booklet

• Within the cell’s nucleus, DNA is divided into 23 pairs of chromosomes (one set of each pair comes from each parent)

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Chromosomes, Genes, and DNA

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The Human Genome Project

• Launched in 1990

• An international collaboration between 20 groups in 6 countries

• In April 2003, it was announced that the sequencing of the human genome was complete

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The Human Genome Project Discoveries

• Humans have only 20,000 to 25,000 genes (same as a mouse)

• Found many potential applications in medicine and pharmaceuticals

• Helped confirm that race has more to do with social and cultural interactions and has no biological basis

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The Role of Mutations

• A change in a gene is called a mutation

• Alternate forms of the same gene are called alleles

• Some mutations are harmful, other mutations can be beneficial, and some have no effect

• Mutations allow for human diversity

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Genetic Inheritance• Alternate forms of

genes, called alleles,are responsible for traits such as eye color

• Alleles can be dominant or recessive

• Most characteristics (such as height or skin color) are determined by the interaction of multiple genes at multiple sites of different chromosomes

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Single-Gene Disorders

• Some diseases are caused by the alteration (mutation) of a single gene

• Autosomal dominant disorder: Mutated gene is on a dominant autosome

• Autosomal recessive disorder: Two copies of a mutated gene on an autosome

• Sex-linked disorder: Mutated gene is on the sex chromosome

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Multifactorial Disorders

• Many diseases and traits can result from interactions between genes and the external environment

• Account for the majority of illnesses and death in the developed world

• Heart disease is one example of a multifactorial disease

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Multifactorial Inheritance in Personality and Behavior

• Genes appear to play a role in personality and everyday behavior

• Differing personality traits, sexual orientations, and inclination towards addiction may be caused by genetic differences

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Chromosomal Disorders• An inherited disorder caused by the addition,

loss, or alteration of an entire chromosome

• May lead to fetal death or death within the first year of life

• Individuals may exhibit a broad range of symptoms, called a syndrome, ranging from characteristic physical traits to developmental delays to growth abnormalities

• Down Syndrome is an example of such a disorder

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Genetic Counseling and Testing

• Genetic counseling helps individuals and families understand genetics, evaluate risks, learn about diagnostic tests, and discuss treatment options

• Popular tests include:– Diagnostic – Predictive – Carrier – Prenatal Screening– Newborn Screening

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Management and Treatment of Genetic Conditions

Treatments may include:

• Dietary Modification

• Medication

• Environmental Adaptation

• Gene Therapy

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Implications of Genetic Research

• Controversial issues in genetic screening and testing

• Issues of privacy and discrimination

• Workplace discrimination• Health insurance discrimination

• Eugenics (selective breeding)