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Chapter 2
Genetics: You and Your
Family Health History
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Genetic Pedigree
Also known as a genogram or family
health tree
A visual representation of your familysgenetic history
A diagram that illustrates the patterns of
health and illness within a family
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What can you learn from your
genetic pedigree?
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 relationship
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What else can you learn from
your genetic pedigree?
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 link than thosemembers who have disease due to poor
health habits
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The basics of heredity The nucleus of every human cell contains 23 pairs
of chromosomes that make up the human genome
Chromosomesare made up of tightly coiledmolecules of DNA
Deoxyribonucleic Acid(DNA) is the genetic material
passed from one generation to the next Genes, the units of heredity, are the segments of
DNA that encode a protein
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The Human Genome Project Launched in 1990
An international collaboration of 20groups in 6 countries
April 2003: announced that the
sequencing of the human genome wascomplete
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The Human Genome Project
discoveries
Humans have only 20,000 to 25,000
genes (same as a mouse)
2% of human DNA occurs in genes
Confirmed that there are no separate
biological races in the human species
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How do genes affect your health?
Alternate forms of genes called allelesare
responsible for different traits such as eye
color
Alleles can be dominant or recessive
A person can inherit two dominant alleles,
one dominant and one recessive allele, or
two recessive alleles
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Genetic mutations Many alleles arise because of mutations that
occur during meiosis
A mutation is an alteration in the DNA
sequence of a gene
Mutations can be neutral, beneficial, or
harmful to an organism and can cause a
disease or disorder
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Single-Gene Disorders Single-gene disorders are diseases caused
by a mutation within one gene
Autosomal dominant disorder: mutated geneis an autosome that is dominant
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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Polygenic and Multifactorial
Disorders
Polygenic disordersare caused by interactions
among mutations in multiple genes
Multifactorial disordersoccur as a result of
Interactions of genes with environmental factors
such as tobacco smoke, pollution, and diet
Multifactorial disordersinclude heart disease,cancer, diabetes, and schizophrenia
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Chromosomal Disorders
An inherited disorder caused by mutations involvingan entire chromosome
Many of these disorders lead to fetal death or deathwithin the first year of life
Individuals with chromosomal disorders exhibit abroad range of symptoms, called a syndrome,
ranging from physical traits to developmentaldelays
Down Syndromeand Turner Syndromeareexamples of such disorders
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Ethnicity and Genetic Disorders Some genetic patterns occur more frequently in
particular groups than in others
Geneticists have confirmed that closely knitpopulations, such as ethnic groups, share genes
The following are types of inherited disorders thatoccur more frequently within certain ethnic groups
Sickle Cell Diseaseaffecting people of African decent Tay-Sachs Diseaseaffecting people of Eastern European
Jewish ancestry
Cystic Fibrosisaffecting white people of European decent
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Genetics and Mental Disorders
Scientific evidence has suggested that a
genetic contribution exists with the following
mental disorders:
Schizophrenia
Mood and Anxiety Disorders
Alzheimers Disease
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Genetics and Behavior
Researchers are studying the genetic
contribution to a variety of behaviors such as:
Personality
Sexual orientation
Addiction
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Genetic Counseling and Testing The goal of genetic counseling is to help
families/individuals understand the role genetics
play in a particular disorder The more popular types of tests are listed below:
Diagnostic Tests
Predictive Tests
Carrier Tests
Prenatal Screening
Newborn Screening
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Management and Treatment of
Genetic Conditions
Dietary Modifications
Medications
Environmental Adaptations
Gene Therapy
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Implications of Genetic Research
Medical advances and cures
Issues in genetic screening and testing
Issues of privacy and discrimination Workplace discrimination
Health Insurance discrimination
Parental eugenics (selective breeding)
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Chapter 2
Genetics: You and Your
Family Health History
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