Table of Contents

1
Table of Contents
Inheritance Patterns and Human Genetics
Chapter 12

• Section 1 Chromosomes and Inheritance
• Section 2 Human Genetics

2
Objectives
Section 1 Chromosomes and Inheritance
Chapter 12

• Distinguish between sex chromosomes and
  autosomes.
• Explain the role of sex chromosomes in sex
  determination.
• Describe how an X- or Y-linked gene affects the
  inheritance of traits.
• Explain the effect of crossing-over on the
  inheritance of genes in linkage groups.
• Distinguish between chromosome mutations and gene
  mutations.

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Chromosomes
Section 1 Chromosomes and Inheritance
Chapter 12

• Genes reside on chromosomes.

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Chromosomes, continued
Section 1 Chromosomes and Inheritance
Chapter 12

• Sex Chromosomes and Autosomes
• Sex chromosomes contain genes that determine an
  organisms sex (gender).
• The remaining chromosomes that are not directly
  involved in determining the sex of an individual
  are called autosomes.

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Karyotypes Male and Female
Section 1 Chromosomes and Inheritance
Chapter 12
6
Chromosomes, continued
Section 1 Chromosomes and Inheritance
Chapter 12

• Sex Determination
• In mammals, an individual carrying two X
  chromosomes is female.
• An individual carrying an X and a Y chromosome is
  male.

7
Effects of Gene Location
Section 1 Chromosomes and Inheritance
Chapter 12

• Sex-Linked Genes and Traits
• Genes found on the X chromosome are X-linked
  genes.
• A sex-linked trait is a trait whose allele is
  located on a sex chromosome.
• Because males have only one X chromosome, a male
  who carries a recessive allele on the X
  chromosome will exhibit the sex-linked trait.

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Effects of Gene Location, continued
Section 1 Chromosomes and Inheritance
Chapter 12

• Linked Genes
• Pairs of genes that tend to be inherited together
  are called linked genes.

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Effects of Gene Location, continued
Section 1 Chromosomes and Inheritance
Chapter 12

• Chromosome Mapping
• The farther apart two genes are located on a
  chromosome, the more likely a cross-over will
  occur.
• Researchers use recombinant percentages to
  construct chromosome maps showing relative gene
  positions.

10
Mutations
Section 1 Chromosomes and Inheritance
Chapter 12

• Germ-cell mutations occur in gametes and can be
• passed on to offspring.
• Somatic-cell mutations occur in body
• cells and affect only the individual organism.

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Mutations, continued
Section 1 Chromosomes and Inheritance
Chapter 12

• Chromosome Mutations
• Chromosome mutations are changes in the structure
  of a chromosome or the loss or gain of an entire
  chromosome.

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Chromosomal Mutations
Section 1 Chromosomes and Inheritance
Chapter 12
13
Mutations, continued
Section 1 Chromosomes and Inheritance
Chapter 12

• Gene Mutations
• Gene mutations are changes in one or more of the
  nucleotides in a gene.

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Gene Mutations
Section 1 Chromosomes and Inheritance
Chapter 12
15
Section 2 Human Genetics
Chapter 12
Objectives

• Analyze pedigrees to determine how genetic traits
  and genetic disorders are inherited.
• Summarize the different patterns of inheritance
  seen in genetic traits and genetic disorders.
• Explain the inheritance of ABO blood groups.
• Compare sex-linked traits with sex-influenced
  traits.
• Explain how geneticists can detect and treat
  genetic disorders.

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Section 2 Human Genetics
Chapter 12
Inheritance of Traits

• Pedigrees
• Geneticists use pedigrees to trace diseases or
  traits through families.
• Pedigrees are diagrams that reveal inheritance
  patterns of genes.

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Pedigree for Cystic Fibrosis
Section 2 Human Genetics
Chapter 12
18
Some Important Genetic Disorders
Section 2 Human Genetics
Chapter 12
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Section 2 Human Genetics
Chapter 12
Genetic Traits and Disorders

• Polygenic Inheritance
• Polygenic characters, such as skin color, are
  controlled by two or more genes.

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Section 2 Human Genetics
Chapter 12
Genetic Traits and Disorders, continued

• Complex Characters
• Complex characters, such as polygenic traits, are
  influenced by both genes and environment.

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Section 2 Human Genetics
Chapter 12
Genetic Traits and Disorders, continued

• Multiple Alleles
• Multiple-allele characters, such as ABO blood
  groups, are controlled by three or more alleles
  of a gene.

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Section 2 Human Genetics
Chapter 12
Comparing Single Allele, Multiple Allele, and
Polygenic Traits
Click below to watch the Visual Concept.
23
Section 2 Human Genetics
Chapter 12
Comparing Complete, Incomplete,and Co-Dominance
Click below to watch the Visual Concept.
24
Section 2 Human Genetics
Chapter 12
Genetic Traits and Disorders, continued

• X-Linked Traits
• The gene for colorblindness, an X-linked
  recessive gene, is found on the X chromosome.

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Section 2 Human Genetics
Chapter 12
Genetic Traits and Disorders, continued

• Sex-influenced Trait
• A sex-influenced trait, such as pattern baldness,
  is expressed differently in men than in women
  even if it is on an autosome and both sexes have
  the same genotype.

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Section 2 Human Genetics
Chapter 12
Detecting Genetic Disease

• Genetic screening examines a persons genetic
  makeup and potential risks of passing disorders
  to offspring.
• Amniocentesis and chorionic villi sampling help
  physicians test a fetus for the presence of
  genetic disorders.

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Section 2 Human Genetics
Chapter 12
Detecting Genetic Disease, continued

• Genetic Counseling
• Genetic counseling informs screened individuals
  about problems that might affect their offspring.

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Section 2 Human Genetics
Chapter 12
Treating Genetic Disease

• Genetic disorders are treated in various ways.
• Among the treatments are symptom-relieving
  treatments and symptom-prevention measures, such
  as insulin injections for diabetes.

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Section 2 Human Genetics
Chapter 12
Genetic Disorder
Click below to watch the Visual Concept.
30
Section 2 Human Genetics
Chapter 12
Treating Genetic Disease, continued

• Gene Therapy
• In gene therapy, a defective gene is replaced
  with a copy of a healthy gene.
• Somatic cell gene therapy alters only body cells.
  
• Germ cell gene therapy attempts to alter eggs or
  sperm.