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(c) 2007 McGraw-Hill Higher Education. All rights reserved.

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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7/19(c) 2007 McGraw-Hill Higher Education. All rights reserved.

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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